Weather and Climate Notes PDF

Weather and Climate Notes (Note to self: it is generally taboo to quote scientific literature, but for the sake of notetaking, I will directly quote the textbook on occasion, such as for definitions of terms. Sorry!!!) 8/30/24 Chapter 1: Introduction to the Atmosphere 1.1 Focus on the Atmosphere...

Weather and Climate Notes (Note to self: it is generally taboo to quote scientific literature, but for the sake of notetaking, I will directly quote the textbook on occasion, such as for definitions of terms. Sorry!!!) 8/30/24 Chapter 1: Introduction to the Atmosphere 1.1 Focus on the Atmosphere - Weather affects us! Who knew!! :D - Some severe weather events: tornados, flash floods, thunderstorms, hurricanes, blizzards (America gets a lot of these, more frequent + severe than other places; we get a variety of weather) - Severe weather impacts lives/health, and economy through agriculture, energy use, water resources, transportation - We also influence the weather: air pollution, climate change - Meteorology: “the scientific study of the atmosphere and the phenomena that we usually refer to as weather.” - Earth’s motion + energy from sun --> reactions in the atmosphere --> all sorts of weather, creating different climates around the world - Weather: “the state of the atmosphere at a given time and place [...] constantly changing, sometimes from hour to hour and at other times from day to day.” - Climate: “a generalization of [weather] variations [...] a description of aggregate weather conditions [...] based on observations that have been accumulated over many decades [...] the average of all weather data, including extremes, that helps to describe the environment of a place or region.” o Not ‘average weather’: “also include[s] variations and extremes, as well as the probabilities that such departures from the norm will take place.” o It is important to know when deviations in weather happen (such as the last frost) - Weather forecasts help us prepare for things! They are more accurate the sooner they are (the forecast for today is more likely to be correct than the forecast for some time next week) - This is why climate is important: it can tell you what the weather tends to be like during a certain period of time, say at the end of spring or in September, helping you  plan farther in advance (or get a sense of whether to bring a winter coat when you move into a new place out-of-state) - Average mins + average maxes + record highs + record lows - “Climate is what you expect, but weather is what you get.” (Climate is, after all, what the weather generally looks like; even hot places get cold!) - 6 most important elements of weather: o 1. Air temperature o 2. Air humidity o 3. Cloudiness (type & amount) o 4. Precipitation (type & amount) o 5. Air pressure o 6. Wind (speed & direction) - Many weather elements have special map symbols - They are interrelated: a change in one often creates change in another - Some natural disasters are geological (volcanos, earthquakes) while others are atmospheric - New severe weather list! o Storm-related: thunderstorms, hurricanes, tornados, blizzards, hail, freezing rain o Not storm-related: heat waves, cold waves, fog, wildfires, drought, floods - Death caused by extreme heat/cold sometimes exceeds death caused by other severe weather! - It costs a lot to clean up after severe weather... 1.2 The Nature of Scientific Inquiry - Science: making observations, and creating explanations for what we observe - Science assumes that there are consistent rules underlying the world’s functioning – rules which we can discover and understand through careful study - We try to understand things so we can predict how they’ll behave! - Hypothesis: “a proposed explanation for a certain phenomenon that occurs in the natural world [...] it must be testable.” o “hypotheses must fit observations other than those used to formulate them in the first place.” o Many get initially discarded after failing rigorous testing, or are later disproven by new data - Theory: “a hypothesis [that] has survived extensive scrutiny [while] competing hypotheses have been eliminated [...] a well-tested and widely accepted view that best explains certain observable facts.”  o Some of the best theories proceed to be comprehensive: for example, the theory of plate tectonics helps explain the genesis of mountains, earthquakes, volcanos, continents, ocean basins, etc. - The scientific method is not rigid, and involves a great amount of creativity, but more often than not includes the following (for the record, I am copy-pasting all of these bullet points): o A question is raised about the natural world. o Scientific data that relate to the question are collected [...]. o Questions that relate to the data are posed, and one or more working hypotheses that may answer these questions are proposed. o Observations, experiments, and models are developed to test the hypotheses. o The hypotheses are accepted, modified, or rejected, based on extensive testing. o Data and results are shared with the scientific community for critical examination and further testing. - Theoretical ideas, testing through simulations and models - Unexpected, enlightening occurrences during experimentation: not pure luck! According to Louis Pasteur, “In the field of observation, chance favors only the prepared mind.” - Methods of science > “THE scientific method” - Scientific Law: “a basic principle that describes a particular behavior of nature that is generally narrow in scope and can be stated briefly—often as a simple mathematical equation [...] shown time and time again to be consistent with observations and measurements [...] rarely discarded but may require modifications to fit new findings.” (think Newton’s laws) 1.3 Earth as a System - Spheres: the “many separate but highly interactive parts” comprising our planet o Each sphere can be studied independently, but they are inextricably linked to one another - Earth System: the “complex and continuously interacting whole” of Earth’s spheres - Usually split into three spheres, obvious from view of Earth from space: o Atmosphere: air o Hydrosphere: liquid water ▪ Of all of Earth’s water: 92.7% is in the oceans, while 0.62%  o Cryosphere: solid water ▪ Of all of Earth’s water: 2.15% ▪ (measurements like this are made via satellite, by the way) o Lithosphere: land o Biosphere: life (not visible from space like other three) - Interface: “a common boundary where different parts of a system interact” o The shoreline is an example: wind creates waves that crash along the sand - Atmosphere o A thin blanket of air covering the surface of the Earth o Provides air to breathe and protection from the Sun o “the energy exchanges that continually occur between the atmosphere and Earth’s surface and between the atmosphere and space produce the effects we call weather.” o No atmosphere = no weather - Hydrosphere o Earth’s water – what makes Earth unique o Always on the move: evaporating into the atmosphere, precipitating down to the ground, running back into bodies of water o Includes: the oceans, which cover 71% of the Earth’s surface; and freshwater (clouds, streams, lakes, glaciers, underground), which comprises a much smaller percentage of Earth’s water, but is vitally important (for instance, clouds are a necessary part of weather – and rain, which is needed for life on land) - Lithosphere o Earth’s rocky outer layer o Uneven surface: mountains and valleys o Otherwise known as the geosphere, which includes the Earth’s mantle and core o Soil can be thought of as part of all four spheres: weathered (hydro/atmosphere) rock debris (lithosphere) and organic matter (biosphere) - Biosphere o All life on Earth o Organisms are not only are affected by their physical environment: they alter it as well o The other three spheres would be drastically different without life o For reference (to other temperatures), the average human body temperature is 37°C - It is important to understand Earth as a system of these spheres, in which they all interact - System: “a collection of numerous interacting parts, or subsystems, that form a complex whole.” Most natural systems transfer matter and energy between regions o Closed System: matter or energy does not enter or leave the system o Open System: matter or energy enter and leave the system o Earth is a closed system for matter, and an open system for energy - Feedback: different than simple cause and effect, as there is a significant change from input to output – an amplification or a deadening o Negative Feedback Mechanism: stabilizes or maintains the system, resisting change (example: clouds, which deaden the amount of solar energy entering the atmosphere – adding solar energy to a cloud just makes more clouds, funnily enough, and the temperature doesn’t increase) o Positive Feedback Mechanism: enhances or promotes change (examples: hurricanes, melting of glaciers) - One of Earth’s subsystems is the hydrologic cycle (all copy-pasted) o Water enters the atmosphere through evaporation from Earth’s surface and transpiration from plants. o Water vapor (water in the gaseous state) condenses in the atmosphere to form clouds... o...which in turn produce precipitation that falls back to Earth’s surface. o Some of the rain that falls onto the land infiltrates (soaks into the ground) and is later taken up by plants or is stored as groundwater, while some flows across the surface toward the ocean. - A change in one part of the Earth system can easily affect the others o Example: heavy rainfall can cause destructive debris flows, dangerous to local plants and animals (hydrosphere --> atmosphere --> lithosphere --> biosphere) - Humans are part of the Earth system too, so whatever we do in one sphere can affect the rest of the system o Burning gasoline/coal o Disposing of waste o Clearing land - The Earth system is powered by energy from the Sun (atmosphere, hydrosphere, Earth’s surface) and interior heat leftover from Earth’s creation and from radioactive decay (volcanos, earthquakes, mountains) 1.4 Composition of the Atmosphere - Air: “a mixture of many discrete gases, each with its own physical properties, in which varying quantities of tiny solid and liquid particles are suspended. The composition [...] is not constant; it varies from time to time and from place to place.” - The atmosphere has a very stable makeup (up to about 80km/50mi) if variable components are removed o Nitrogen o Oxygen o Small amounts of other gases, including argon, carbon dioxide, and water vapor - Primitive atmospheric composition (very different from today): hydrogen, helium, methane, ammonia, carbon dioxide, and water vapor; most ended up scattered into space, due to lightness or solar winds - Outgassing: a process “through which gases trapped in the planet’s interior are released.” o Created Earth’s first lasting atmosphere: massive gas output from lots of internal heating and fluid movement o Early atmosphere: mostly water vapor, carbon dioxide, sulfur dioxide, minimal nitrogen, and small amounts of other gases - Molecular/free oxygen (oxygen not bound to other elements), O2, was not significantly present in Earth’s atmosphere for the first 2 billion years of the planet’s history - Earth’s surface cooled --> water vapor condensed and formed clouds --> torrential rains filled low-lying areas to create the oceans --> cyanobacteria in the oceans begin to perform photosynthesis, releasing oxygen into the water (nearly 3.5 billion years ago) --> oxygen consumed by other molecules in the water, until they no longer needed it, and more organisms begin producing oxygen --> oxygen begins to build up in the atmosphere - Oxygen levels only increased to around today’s levels 550 million years ago, leading to a new abundance of aerobic organisms - In addition, upon absorbing UV radiation, O2 rearranges to become O3 (ozone), which would go on to protect life on land from the sun’s harmful radiation as the ozone layer in the stratosphere (UV is particularly bad for DNA; marine life was protected by the water) - Breakdown of clean, dry air in today’s atmosphere o Nitrogen (N2): 78.084%  o Oxygen (O2): 20.946% o Argon (Ar): 0.934% o Carbon Dioxide (CO2): 0.0405% (405 parts per million) o Neon (Ne): 0.00182% (18.2 ppm) o Helium (He): 0.000524% (5.24 ppm) o Methane (CH2): 0.00015% (1.5 ppm) o Krypton (Kr): 0.000114% (1.14 ppm) o Hydrogen (H2): 0.00005% (0.5 ppm) - Despite making up most of air, and being very important for life, nitrogen and oxygen don’t really affect the weather - Variable components of the atmosphere, based on time and place -- small percentage of atmospheric composition, big impact on weather and climate: o Carbon dioxide ▪ Absorbs energy efficiently, thus influencing the heating of the atmosphere ▪ Generally uniform proportion across the globe and at different elevations, but is variable temporally: for over a century, its atmospheric percentage has been steadily rising ▪ Increased burning of fossil fuels (coal and oil) leads to the increase in CO2 ▪ Some excess CO2 is absorbed by the ocean or used by plants, but over 40% is still in the air ▪ By sometime in the second half of the 21st century, atmospheric carbon dioxide is expected to be double its pre-industrial level ▪ This CO2 has contributed to global warming o Water vapor ▪ Humidity: “the amount of water vapor in the air.” ▪ The amount of water vapor in the air varies considerably (from almost 0 to 4%) ▪ The source of all clouds and precipitation ▪ Absorbs heat given off by Earth as well as some solar energy ▪ Latent Heat: the energy absorbed or released by water as it changes states; “water vapor in the atmosphere transports [it] from one region to another, and it is the energy source that helps drive many storms.” ▪ It is evaporated water (evaporation is caused by heat), so the hotter the atmosphere is, the more water vapor ends up in the atmosphere o Aerosols  ▪ The large quantity of tiny solid and liquid particles suspended in the atmosphere by atmospheric movement ▪ Visible dust (which can obscure the sky) is too heavy to remain in the atmosphere long ▪ Many other particles are microscopic and so can stay suspended for a long time (these can be natural or man-made) ▪ Most numerous in the lower atmosphere, near the Earth’s surface (whence they originate); aerosols in the upper atmosphere can come from rising currents bringing lower particles, or from the disentegrated matter of meteoroids ▪ Very important meteorologically: they provide a surface on which water vapor can condense (to create clouds or fog), they can absorb or reflect radiation from the Sun (in extreme cases, measurably limiting the amount of sunlight reaching Earth), and they contribute to the red/orange color of sunrises and sunsets ▪ SOME AEROSOLS ARE CONSIDERED POLLUTANTS o Ozone ▪ Three oxygen atoms, O3, instead of breathable oxygen’s two (O2) ▪ Accounts for only 3 out of every 10 million molecules! ▪ Not distributed uniformly throughout the atmosphere: concentrated in the stratosphere, 10-50km (6-31mi) above Earth’s surface ▪ In the stratosphere, UV rays split O2 into single O molecules; a neutral molecule catalyzes the reaction between O2 and O into O3 ▪ Ozone is concentrated in the stratosphere, as there is enough UV radiation to produce O, and there are enough gas molecules to catalyze the reaction to produce O3 ▪ Ozone is essential to land-dwelling organisms: it absorbs large amounts of UV radiation, making life on land hospitable where it otherwise wouldn’t be Thus, any reduction in ozone in the atmosphere can be catastrophic for life on land – and it is indeed vulnerable to human activities, even if it is high up in the atmosphere Ozone depletion has occurred worldwide over the past 3 decades, especially over the poles o “What you spray here does not stay here” -- obviously CFCs (mentioned below) were not produced in Antarctica, but they sure as hell ended up there to create the ozone hole (which, notably, is now fixed due  to the impact of the Montreal Protocol, also mentioned below) o THE OZONE HOLE HAS NOTHING TO DO WITH GLOBAL WARMING. IT WAS NOT CAUSED BY GLOBAL WARMING, AND IT DID NOT CONTRIBUTE TO IT Chlorofluorocarbons, or CFCs (developed in the 30s and used as coolants in air conditioners and refrigerating equipment, as cleaning solvents, and as propellants for aerosol sprays), are inert in the lower atmosphere, causing some of them to rise to the ozone layer, where they destroy thousands of ozone molecules by releasing a single catalyzing chlorine atom o In humans, UV radiation causes or promotes sunburn, skin cancer, immune system impairment, cataracts, and blindness o The 1987 Montreal Protocol was a treaty developed to halt the production and use of CFCs, ratified by over 190 nations; it has induced strong action to that effect, but CFC molecules spend a long time active in the atmosphere, so there is no rapid fix ▪ Ozone is a pollutant when produced at ground level, damaging vegetation and harming human health; it is a major component in photochemical smog, a mixture of gases and particles emitted by motor vehicles and industries IN THE LOWER ATMOSPHERE, OZONE IS CONSIDERED A POLLUTANT ▪ OZONE IS NOT RELATED TO THE GREENHOUSE EFFECT AT ALL 1.5 Vertical Structure of the Atmosphere - The atmosphere is very thin when compared to the bulk of the solid Earth - It does not end abruptly in space – it dissipates out, gas molecules becoming more and more sparse until they’re undetectable - Atmospheric Pressure: “the weight of the air above.” o Pressure is a force applied over an area (pressing down on a table with your finger is just a force; doing so with your whole palm is exerting pressure) - The millibar (mb) is used to measure atmospheric pressure - At sea level, the average air pressure is slightly above 1,000 mb, a weight of 14.7 lbs per square inch; the pressure of higher altitudes, having less air on top of them, is lower - “The rate of pressure decrease with an increase in altitude is not constant. Pressure decreases rapidly near Earth’s surface and more gradually at greater heights. Put another way, the figure shows that the vast bulk of the gases making up the atmosphere is near Earth’s surface and that the gases gradually merge with the emptiness of space.” - - 50% of atmosphere within an altitude of of 5.6km (3.5mi) - 90% of atmosphere within an altitude of 16km (10mi) - 99% of admosphere within an altitude of 30km o For reference, Mount Everest is 9km tall; the mariana trench is 11km deep; the ocean’s average depth is 4km - Less air than in any artificial vacuum at 100km, but it’s still there! In fact, the atmosphere – air molecules – continue into space for thousands of km above Earth’s surface - “to say where the atmosphere ends and outer space begins is arbitrary and depends on what phenomenon one is studying.” o The atmosphere is, one could say, a negotiation between space and the surface of the Earth - Air pressure falls at a decreasing rate as altitude increases (I just know you can do some calculus to this) - Air is highly compressible: “the gases that make up air expand with decreasing pressure and become compressed with increasing pressure.” - How to figure out what percentage of the atmosphere is below you based on your altitude and the air pressure - Air temperature decreases as altitude increases: hence, snow-capped mountains – though it levels off between 8-12km (5-7.5mi), and the shifts in temperature vary based on different levels of the atmosphere - - ^The avergage atmospheric temperature profile. Day-to-day, though, it is variable, especially in the lower atmosphere - Homosphere: zone of homogeneous composition extends up to 80km (mesopause) - Heterosphere: zone of heterogeneous composition extends from mesopause through thermosphere - Planetary Bound of Atmosphere: 1-2km level of atmosphere - Layered structure according to atomic weight: o Hydrogen o Helium o Oxygen o Nitrogen - Troposphere: “The bottom layer in which we live, where average temperatures decrease with an increase in altitude [... the name] means the region where air “turns over,” a reference to the appreciable vertical mixing of air in this lowermost zone.” o Note: The temperature at 2 meters of altitude is basically surface temperature o Environmental Lapse Rate: “The temperature decrease in the troposphere” ▪ Normal Lapse Rate: the average value of the environmental lapse rate, "6.5°C per kilometer (3.5°F per 1000 feet)” ▪ The environmental lapse rate is not regular, and highly variable: it must be regularly measured by radiosonde  ▪ Radiosonde: “an instrument package that is attached to a balloon and transmits data by radio as it ascends through the atmosphere”. “[They] are used to measure the actual environmental lapse rate, as well as gather information about vertical changes in air pressure, wind, and humidity.” ▪ Weather fluctuations, season, and location can all cause variations in the environmental lapse rate over a day ▪ Temperature Inversions: “shallow layers where temperatures actually increase with height [...] observed in the troposphere [...] reversals” o Tropopause: “the top of the troposphere”, where the temperature ceases to decrease ▪ The elevation of the tropopause (where the troposphere ends and where the tropopause begins) is, on average, 12km (7.5mi), but is higher in the tropics – over 16km (10mi) – and lower in polar regions – 7-8km (~5mi) ▪ “Warm surface temperatures and highly developed thermal mixing as the warmed air rises are responsible for the greater vertical extent of the troposphere near the equator.” ▪  o Basically all significant weather phenomena occur in the troposphere (most clouds, all precipitation, all violent storms), hence it is meteorologists’ primary focus and called the “weather sphere” o Unstable due to cold on hot – this is what makes the troposphere energetic and gives us weather - Stratosphere: the layer of atmosphere above the troposphere, where “the temperature at first remains nearly constant to a height of about 20 kilometers (12 miles) before it begins a sharp increase that continues until the stratopause is encountered” o Stratopause: the upper boundary of the stratosphere, 50km (30mi) above Earth’s surface o High concentration of ozone, which, by absorbing energy from the sun, accounts for the increase in temperature o "Although the troposphere is dominated by large-scale turbulence and mixing, very little vertical mixing occurs in the stratosphere. This is because the stratosphere experiences a temperature inversion, where cold air lies beneath warm air, in contrast to the opposite occurrence in the troposphere.” o Stable due to hot on cold - Mesosphere: the layer of atmosphere above the stratosphere, where “temperatures decrease with height until the mesopause [...] is reached” o Mesopause: the upper boundary of the mesosphere, “located about 80 kilometers (50 miles) above the surface, where the average temperature approaches a chilly −90°C (−130°F)—the coldest temperatures anywhere in the atmosphere.” o Abundant vertical mixing on account of temperatures decreasing with height o Inaccessible to highest airplanes and research balloons and lowest satellites, making it the least-explored layer of the atmosphere - Thermosphere: the layer of atmosphere above the mesosphere, and the outermost layer, with no well-defined upper boundary; “temperatures again increase as oxygen and nitrogen atoms absorb very shortwave, high-energy solar radiation” o "only a tiny fraction of the atmosphere’s mass”; rarified, low-pressure o Temperatures rise to over 1000°C (1800°F)! But if an astronaut were to stick their hand into the thermosphere, they wouldn’t feel hot. The gases in the thermosphere move at high speeds, making them hot by temperature’s definition), but the molecules are so few and far between that their thermal energy is very low  ▪ “the temperature of a satellite orbiting Earth in the thermosphere is determined chiefly by the amount of solar radiation it absorbs, and not by the high temperature of the almost nonexistent surrounding air.” o Unstable due to cold on hot - Ionosphere: an electrically-charged layer of the atmosphere situated in the lower portion of the thermosphere – between 40-80km (50-250mi) above the Earth’s surface o Ionization: “a process in which the affected molecule or atom loses one or more electrons and becomes a positively charged ion, and the electrons set free then travel as electric currents.” o Nitrogen molecules and oxygen atoms are ionized by absorbed short-wave, high-energy solar radiation o Has little to no impact on weather o The site of the auroras: aurora borealis (northern lights) and aurora australis (southern lights): ▪ “Sometimes the displays consist of vertical streamers in which there can be considerable movement. At other times, the auroras appear as a series of luminous expanding arcs or as a quiet glow that has an almost foglike quality.” ▪ Aligned with Earth’s magnetic poles ▪ Correlated with solar storms, like solar flares ▪ Solar Flares: “massive magnetic storms on the Sun that emit enormous quantities of fast-moving atomic particles. As these charged particles (ions) approach Earth, they are captured by its magnetic field, which in turn guides them toward the magnetic poles. Then, as the ions impinge on the ionosphere, they energize the atoms of oxygen and molecules of nitrogen and cause them to emit light— the glow of the auroras.” Solar storms are associated with sunspots, so there are more auroras the more sunspots there are 9/3/24 Lab - Weather: Atmospheric conditions at certain place and time (things like temperature, humidity, air pressure, and density)  - Climate: Patterns of weather conditions over decades - “Climate is what you expect, weather is what you get” Mapping - Different (2D) map projections: Mercator, Gall-Peters, Goode-Homolosine, Watermelon, Albers, Robinson o It’s hard to reflect a 3D shape in 2D! Different projections sacrifice different things (size, shape) to do so - “Maps are not neutral. Maps are not, inherently, ‘true.’ Maps have points of view. Maps carry cultural bias. Maps tell stories.” -Elizabeth Alexander - Global Address o Latitude (horizontal, read north-south); goes from 0 to 90 in either direction (north/positive or south/negative) o Longitude (vertical, read east-west); goes from 0 to 180 in either direction (east/positive or west/negative) o Equator – 0 degrees latitude; widest part of the earth o Prime Meridian – 0 degrees longitude; passes through British Royal Observatory o In more detailed maps, latitude and longitude fractions of degrees can be used. (1 degree is 60 minutes, 1 minute is 60 seconds) ▪ Not time! Just same terminology! o Distance between latitude and longitude lines ▪ Each degree of latitude is approximately 69 miles apart; latitude can also be estimated by multiplying the circumference of the Earth (40,000km) by the proportion of degrees traveled out of 360 How many km have you moved by traveling 20 degrees north? o 20/360 * 40,000km = 2,222.22km ▪ You can’t really do it with longitude lines, because the distance between them is smaller near the poles and greater near the equator o High/middle/low latitude – refers to the number ▪ Low latitude has a small latitude number, north or south (near equator) ▪ High latitude has a big latitude number, north or south (near poles) ▪ Middle latitude is... in the middle Measurements and Conversions - Area = length * width - Volume = length * width * height - Density = mass/volume - Speed = distance/time - Pressure = mass/length * time^2 - Km –x1000-> m –x1000 -> cm –x1000 -> mm - Conversion chart: left to right = multiply, right to left = divide o Doing it in the opposite direction will give basically the same answer, but slightly off - Original units should cancel out - Don’t forget to show your work and include the units! - Original amount * (unit you want/unit you have) = converted amount o For (unit you want/unit you have), have it as 1/conversion when dividing and conversion/1 when multiplying - If you’re converting units to some power (say, ft^2 to m^2), you must do the conversion as many times as the power (so ft^2 x ft/m x ft/m) - Finding the conversion factor o At 1000ft, the atmospheric pressure inHg is 28.86 inHg, and 977.166 millibars. A pressure of 50 inHg would be what in mb? ▪ 50inHg x 977.166m/28.86inHg ▪ Simplify: 50inHg x 33.86mb/1inHg = 1,693mb - Isolines/Isotherms: a way to display gradients of things like temperature, elevation, and pressure across space. Isolines connect points of equal value. o Isoline guidelines: ▪ Isolines should either form a closed loop or run off the sides of the map ▪ All values on one side of the line will be higher than the line value and the value on the other side should be lower ▪ There should be a consistent factor that the isolines increase by and it should be apparent in the key ▪ The lines should not intersect ▪ Only values of equal value should be together in a line ▪ Estimate between data points where integer values would be for isolines ▪ (These guidelines are not the observations we’ll be making.) - High gradient: lots of change, isolines close together - Low gradient: not a lot of change, isolines far apart 9/6/24 Chapter 2: Heating Earth’s Surface and Atmosphere 2.1 Earth-Sun Relationships - The Earth receives solar energy unequally: the amount at any given location depends on latitude, time of day, and season of the year o An easy example is the poles vs the tropics/equator - This uneven heating of Earth’s surface is what creates wind and ocean currents, which transport heat to the poles in a constant attempt to balance the energy inequality - If there were no sun, we’d have no wind or ocean currents; we’d have no weather. So long as the sun persists, so do they - Earth moves in two ways: it rotates about an axis and orbits around the sun - Rotation: “the spinning of Earth on its axis, which is an imaginary line connecting the North Pole to the South Pole[. It] takes 24 hours (1 day) and produces the cycle of day and night." o Spins over 1,000 km/hr (over approximately 24 hrs) - Orbit: Earth’s “slightly elliptical [revolution] around the Sun that takes about 365¼ days (1 year). Because Earth’s orbit is not perfectly circular, the distance [between the Earth and the Sun] varies during the year” o Revolves 67,000 km/hr (over approximately 365 days) o Leap days help us keep our dates in line with the seasons we associate with them - Perihelion: A position Earth takes “Each year, on about January 3, [when] our planet is about 147 million kilometers (91.5 million miles) from the Sun, closer than at any other time.” o The Earth receives up to 7% more energy than at the aphelion (this has only a minor role in determining the seasons) - Aphelion: A position Earth takes each year, “on July 4, [when] Earth is about 152 million kilometers (94.5 million miles) from the Sun, farther away than at any other time.” - Average distance between the Earth and the Sun: 150 million km (93 million mi) - The length of daylight gradually changes over the span of a year, with summer having longer daylight and winter having shorter o More noticeable farther from equator: the north pole gets continuous daylight from March 21-August 21!  o Longer daylight = warmer temperatures, which is part of why the temperature is higher in summer and lower in winter - The sun’s angle/altitude over the horizon (the angle between the ray of light and the surface) affects the amount of solar energy reaching Earth’s surface o When the Sun has a 90° angle (directly overhead), the solar rays are most concentrated and intense; the rays are dimmer and more spread out at lower angles ▪ The lower the angle, the points at which the rays of light hit the ground are farther apart, making the solar energy more diffused ▪ ▪ ▪ Beam Spread = 1 unit / sine(Sun angle) o Tropical areas get higher Sun angles more often, while polar areas get lower Sun angles o Noon Solar Time: “when the Sun is highest in the sky.” o The Sun’s angle also depends on the time of year: for a place like Chicago, the highest noon solar time is from June 21-22 (this would coincide with the longest period of daylight); as the season changes from summer to fall and then winter, however, the noon Sun gets gradually lower in the sky (coinciding with a decrease in daylight and earlier sunsets) -- the lowest noon solar time and earliest sunset are on December 21-22.  ▪ There is a temperature lag, though – the lowest temperatures of the year are not during this lowest noon solar period, but rather a few weeks later, in January o The angle of the Sun also determines how far through the atmosphere a ray of light must travel to reach Earth’s surface: 90° angles hit the Earth straight- on, taking the most direct and shortest path; smaller angles spend more time traveling through the atmosphere before reaching the surface. Any time the energy spends in the atmosphere is time it can be absorbed or dispersed, meaning smaller angles of sunlight are more likely to diminished on their approach o - The Earth’s orientation to the sun continually changes, causing variation in the angle of the Sun and the length of daylight - Plane of the Ecliptic: “the plane of [the Earth’s] orbit around the Sun” - Inclination of the Axis: the Earth’s axis’ tilt, 23.5° from the plane of the ecliptic - The Earth’s axis is not perpendicular to the plane of the ecliptic, instead having an inclination of the axis; if not for this inclination, Earth would have no seasons, as the angle of sunlight would be consistent year-round - “Because the axis is always pointed in the same direction (toward the North Star), the orientation of Earth’s axis to the Sun’s rays is constantly changing” - - On one day in June, because of Earth’s position in orbit, the northern hemisphere is inclined 23.5° towards the Sun; inversely, on one day in December, the northern hemisphere is inclined 23.5° away from the Sun o On the days between, the northern hemisphere’s inclination towards or away from the sun is less o On account of this change in orientation, the latitude at which the Sun’s rays strike the atmosphere at an angle 90° shifts across the year from 23.5° latitude north of the equator to 23.5° latitude south of the equator ▪ “this migration causes the angle of the noon Sun to vary 47° (23½° + 23½°) for all midlatitude locations during a year. New York City, for instance, has a maximum noon Sun angle of 73½° when the Sun’s vertical rays have reached their farthest northward location in June, and a minimum noon Sun angle of 26½° 6 months later—a difference of 47°” ▪ “a city on the equator will experience an annual migration of half that amount, 23½°.” - Only one line of latitude receives 90° rays of sunlight on any given day; the angle decreases as we move north or south of that latitude: “Thus, the closer a place is situated to the latitude receiving the vertical rays of the Sun, the higher will be its noon Sun, and the more concentrated will be the radiation it receives.” - Solar Declination/Subsolar Point: “the latitude receiving the vertical [90°] rays of the Sun [at solar noon]” - Zenith Angle: The angle between a point directly overhead and the Sun at solar noon (the number of degrees latitude a location is from the subsolar point) - Solar Elevation/Sun Angle: The angle of the Sun above the horizon at solar noon - 1° of latitude away from the subsolar point = Sun angle is 1° less - Noon sun angle = 90° – (current latitude +– subsolar point) o (+ if in different hemisphere, - if not) o Or 90 – zenith angle o Where I am: about 41° N; summer solstice subsolar point is the tropic of cancer, 23.5° N; 41° - 23.5° = 17.5°; 90° - 17.5° = 72.5° (my sun angle during the summer solstice) - - Summer solstice (June 21/22): subsolar point is the tropic of cancer, 23.5° north of equator -- “official” start of summer - Winter solstice (December 21/22): subsolar point is the tropic of capricorn, 23.5° south of equator -- “official” start of winter - Vernal equinox (March 21/22) and autumnal equinox (September 22/23): subsolar point is the equator -- “official” start of spring and autumn respectively - It’s perfectly possible (and common) for the weather typical of a season to occur before or after its “official” period o Difference between astronomical seasons (delineated by the solstices/equinoxes mentioned above) and climatological seasons, the latter of which actually coinciding with the weather associated with each season Season Astronomical Climatological Season Season Spring March 21/22 - March, April, May June 21/22 Summer June 21/22 - June, July, August Sept. 22/23  Autumn Sept. 22/23 - September, October, November Dec. 21/22 Winter Dec. 21/22 - December, January, February March 21/22 o Being more accurate to our notion of the seasons (which is weather-based), meteorologists are more likely to find the climatological definition useful and relevant - Solar Insolation: the total incoing solar radiation (depends on number of daylight hours AND Sun angle) - Circle of Illumination: "the boundary separating the dark half of Earth from the lighted half.” - Length of daylight is determined by Earth’s position relative to Sun’s rays: established by comparing dark and light fractions of line of latitude across circle of illumination o In summer, all of the northern hemisphere has longer daylight than darkness o In winter, all of the northern hemisphere has longer darkness than daylight o o Seasonal change of daylight hours is the main factor affecting seasonal temperature change o o Midnight Sun: “a natural phenomenon in which the Sun is visible at midnight” o The farther north you are, the longer your daylight is on summer solstice (places on or north of the arctic circle, 66.5° N, experience the midnight Sun) ▪ Sun does not set for 1 day – arctic circle  ▪ Sun does not set for 4 months – 80° N ▪ Sun does not set for 6 months – the north pole ▪ The sun never drops below the horizon! ▪ The equivalent latitudes in the south experience that amount of darkness during the summer solstice - - All locations on the same latitude line get the same Sun angle and daylight hours o “If the Earth–Sun relationships were the only controls of temperature, we would expect these places to have identical temperatures as well. This is not the case. Other factors, such as a location’s elevation or its proximity to a large body of water, also influence local temperature” 2.2 Energy, Temperature, and Heat - Matter and energy - Energy: “having the capacity for doing work, such as making an object move [...] energy takes many forms and can also change from one form to another.” - Energetic: energy exchange between space and atmosphere, and between the atmosphere and the Earth’s surface - Some forms of energy: thermal, chemical, nuclear, radiant, and gravitational energy - Kinetic Energy: “Energy associated with an object by virtue of its motion” o Increased speed or mass increase kinetic energy o “when a solid, liquid, or gas is heated, its atoms or molecules move faster, and the material possess more kinetic energy.” - Potential Energy: “has the potential or capacity to do work.” o Gravitational potential energy, chemical potential energy - Collquially, “temperature” describes how hot or cold something is using a standard measure - Temperature: “formally defined as a measure of the average kinetic energy of the atoms or molecules in a substance.” o When heated --> atoms/molecules move faster --> higher temperature o When cooled --> atoms/molecules move slower --> lower temperature - Temperature is NOT a measure of an object’s TOTAL KINETIC ENERGY  o A cup of boiling water has a higher temperature than a bathtub of lukewarm water, but it has a smaller total kinetic energy because it has much less water (a larger quantity of ice would melt in the tub than in the cup) o “The temperature of the water in the cup is higher because the atoms and molecules are vibrating faster, but the total amount of kinetic energy (also referred to as heat, or thermal energy) is much smaller because there are far fewer atoms and molecules. ▪ So, scientifically, the cup of boiling water has less heat than the bathtub of lukewarm water! ▪ Measured in degrees (Farenheit, Celsius, Kelvin) - Heat: “energy transferred into or out of an object because of temperature differences between that object and its surroundings.” o Your hands are colder than a mug of hot cocoa, so heat travels from the mug to your hands (making them feel warm) o Your hands are warmer than an ice cube, so heat travels from your hands to the ice cube (making them feel cold) o “Heat flows from a region of higher temperature to a region of lower temperature. Once the temperatures become equal, heat flow stops.” o Measured in calories, joules (energy measurements) - HEAT IS THE TOTAL ENERGY OF THE MOTION OF THE MOLECULES IN A SUBSTANCE; TEMPERATURE IS THE AVERAGE ENERGY - Thermal Energy (AKA Heat): “the energy contained in a substance as a result of its temperature” (hot objects have more thermal energy than cold objects) o To go back to the cup and bathtub from before: if the cup held the same amount of water as the bathtub, it would have more heat/thermal energy because it has a higher temperature. However, the quantity of water is smaller - Phase Change: The process by which “Heat is released or absorbed when water changes from one state of matter to another” o During evaporation, water absorbs heat from its environment, causing its molecules to move faster; when this movement is great enough to overcome the surface tension holding the water molecules together, some of the molecules escape – they evaporate – to become water vapor. Because it is these most energetic molecules that escape, the average kinetic energy/temperature of the remaining water decreases. “Therefore, evaporation is considered a cooling process because it removes heat from the environment." (this is why you feel cold after stepping out of a pool or shower) - Latent Heat: “the energy required to convert a solid into a liquid (or vapor), or a liquid into a vapor, without a change of temperature." o This is the energy that was absorbed by the water molecules that turned highly energetic and escaped; called latent, or hidden, because the energy is stored inside these molecules instead of being out in the environment o This energy is eventually released back into the environment (usually the atmosphere) during condensation – such as during the formation of clouds, in which water vapor returns to being a liquid ▪ As condensation (the opposite of evaporation) releases heat back into the environment, it is considered a warming process o (heat energy = latent heat) o ▪ It takes less heat energy to move directly from solid to gas or gas to solid than to go through each state of matter in steps (100°C vs 620°C)  - Sensible Heat: “the heat that we can feel and measure with a thermometer but that does not involve a phase change.” o Can be sensed and, like latent heat, can be moved from one location to another 2.3 Mechanisms of Heat Transfer - “The flow of energy can occur in three ways: conduction, convection, and radiation [...] Although we will present them separately, all three mechanisms of heat transfer can operate simultaneously and, working in tandem, these processes can transfer heat between the Sun and Earth and between Earth’s surface, its atmosphere, and outer space.” - - Conduction: “the transfer of heat through molecular collisions from one molecule to another.” o Needs an agent o Remember, heat is the fast movement of molecules! So they can bump into each other, causing molecules down the line to move fast as well – and be hot o Metals are good conductors (heat travels well through it) o Air is a good insulator (heat does not travel well through it) ▪ Fun fact: the reason why bathroom tile feels so much colder than the bathmat despite having the same temperature is that the tile is a better conductor of heat, meaning the heat from your feet travels to the tiles faster, making your feet colder, than it would for the bathmat (which is an insulator) o “conduction is important [to meteorology] only between Earth’s surface and the air immediately in contact with the surface. Conduction is the least significant means of heat transfer for the atmosphere as a whole, and we can disregard it when considering most meteorological phenomena.” - Convection: “heat transfer that involves the actual movement or circulation of a substance.” o Needs an agent  o For water in a pan, the heat from the pan warms up the water at the bottom via conduction. This heat causes the water molecules to move, making the water less dense and more buoyant. This buoyant water rises, while the dense (non-heated) water sinks; the water at the top now cools off, and the water on the bottom warms up, continuing the cycle. ▪ This is called conductive circulation! o The same happens with air in the atmosphere, with the warm ground heating up the bottom layer of air ▪ Thermal: a warm parcel of rising air ▪ The rising thermals, aside from carrying heat, also carry water vapor, which is what causes more clouds to form on warm summer afternoons ▪ o “On a much larger scale is the global convective circulation of the atmosphere, which is driven by the unequal heating of Earth’s surface. These complex movements are responsible for the redistribution of heat between hot equatorial regions and frigid polar latitudes” o Convection is vertical; advection is horizontal o Advection: “the horizontal component of airflow”, including wind ▪ This is what brings freezing Canadian air into the midwest during January to make bitterly cold weather, among other things - Radiation: “the only mechanism that can transfer thermal energy through the vacuum of space and thus is responsible for solar energy reaching Earth.” o Does NOT need an agent o A self-propagating wave that can travel through the void of space ▪ Wave: any signal that repeats itself after a certain period; all are described by amplitude, wavelength, period o Radiation/electromagnetic radiation ▪ Has a constant speed, the speed of light o o The Sun emits visible light, ultraviolet, and infrared o Speed of light: 300,000 km (186,000 mi) per sec o Wavelength: “the distance from one crest to the next” within electromagnetic waves ▪ Used to classify types of radiation o Infrared Radiation: radiation “Located adjacent to the color red, and having a longer wavelength [...] cannot be seen by the human eye but is detected as heat.” o Ultraviolet Radiation: radiation “located next to violet [...] consists of shorter wavelengths that may cause skin to become sunburned.” o “When an object absorbs any form of electromagnetic energy, the waves excite subatomic particles (electrons). This results in an increase in molecular motion and a corresponding increase in temperature.” ▪ The Sun’s waves of radiant energy do this to our atmosphere, Earth’s surface, and us! o Short-wave radiation is more energetic than long-wave radiation, which is why UV can give us suburns while infrared cannot; the shorter the wavelength, the more concentrated and harmful it is ▪ “The UV index is determined by taking into account the predicted cloud cover and reflectivity of the surface, as well as the Sun angle and atmospheric depth for each forecast location. Because atmospheric ozone strongly absorbs ultraviolet radiation, the extent of the ozone layer is also considered.” o The Sun emits all forms of radiation: of the energy it emits, 49% is infrared, 43% is visible light, 7% is ultraviolet, and less than 1% is X-rays, gamma rays, microwaves, and radio waves o ▪ ^ When talking about solar radiation in this class, we mostly focus on visible light and infrared radiation ▪ The atmosphere is largely transparent to visible light, which is why we can see things! This is also the sun’s most intense radiation o Laws of Radiation: ▪ 1) “All objects continually emit radiant energy over a range of wavelengths." (So long as its temperature is above absolute zero) ▪ 2) “Hotter objects radiate more total energy per unit area than do colder objects.” ▪ 3) “Hotter objects radiate energy in the form of shorter-wavelength radiation than do cooler objects.” The hotter the radiating body, the shorter the wavelength of maximum radiation 𝐶 Wien’s Displacement Law: 𝜆 max = 𝑇 o 𝐶 = 2898𝜇𝑚𝐾 o 𝜆𝑠𝑢𝑛 = 0.483 o 𝜆𝑒𝑎𝑟𝑡ℎ = 9.66 ▪ 4) “Objects that are good absorbers of radiation are also good emitters.” Earth’s surface and Sun both absorb and radiate with almost 100% efficiency Blackbodies: “Bodies that absorb and radiate all wavelengths well” The gases in our atmosphere are selective absorbers and emitters of radiation  o “most atmospheric gases are good absorbers (emitters) of radiation only in certain wavelengths but are poor absorbers(emitters) in other wavelengths.” o Stefan-Boltzman Law: 𝐸 = 𝜎𝑇 4 𝑊 ▪ 𝜎 = 5.67 ⋅ 10−8 𝑚 2 𝐾4 (constant) ▪ Small additions of temperature to the Earth System change the overall temperature more than you’d expect 2.4 What Happens to Incoming Solar Radiation? - - “Solar radiation may be transmitted, absorbed, or reflected and scattered once it reaches the atmosphere.” - Radiation Fluxes o SW↓: shortwave; global solar radiation received at Earth’s surface – depends on location, season, time of day, and cloudiness o SW↑: shortwave; solar radiation reflected by the surface – depends on surface albedo o LW↑: longwave; infrared radiation emitted by the surface – depends on surface temperature o LW↓: infrared radiation received at surface (from the atmosphere) – depends on atmospheric temperature, moisture, and clouds  o Net surface radiation = SW↓ - SW↑ + LW↓ - LW↑ ▪ When greater than zero, there is an energy surplus Surplus radiation can be expended in three general ways: o Sensible Heat Flux: energy is expended in heating the air at Earth’s surface o Soil Heat Flux: energy is expended in heating the soil o Latent Heat Flux: energy is used in evaporating moisture from the surface ▪ When less than zero, there is an energy defecit - - Transmission: “the process by which energy passes though the atmosphere (or any transparent media) without interacting with the gases or other particles in the atmosphere.” - Absorption: “The amount of energy absorbed by an object depends on the wavelength of the radiation and the object’s absorptivity [...] The atmosphere is a less effective absorber because gases are selective absorbers (and emitters) of radiation.” o When energy is absorbed, the kinetic energy increases - Reflection: “the process whereby light bounces back from an object at about the same angle and intensity at which it was received.” o Albedo: “The fraction of radiation that is reflected by an object” ▪ The atmosphere, overall, has a 30% albedo o Light-colored objects have a higher albedo than dark-colored objects  o Land has a higher albedo than water o Angle of Impingment: the angle of reflection - Scattering: “a general process in which radiation bounces off an obstacle in many directions.” o “Although incoming solar radiation travels in a straight line, small dust particles and gas molecules in the atmosphere scatter some of this energy in different directions. The result, called diffused light, explains how light reaches the area under the limbs of a tree and how a room is lit in the absence of direct sunlight.” o About half of of the solar radiation absorbed at Earth’s surface is diffused light o Rayleigh Scattering: “Scattering of visible light by atmospheric gases” o Mei Scattering: “Scattering of visible light by dust or smoke” - Why is the sky blue during the day? o Rayleigh scattering! o “Atmospheric gases scatter shorter-wavelength (blue/violet) light more effectively than they scatter longer-wavelength (red/orange) light. Because shortwave radiation is selectively scattered, when you look in any direction away from the direct Sun, you observe the short-wavelength (blue) light” - Why is the Sun/sky red during sunrise and sunset? o Rayleigh scattering! o “The Sun appears reddish when viewed near Earth’s horizon at sunrise or sunset because solar radiation must travel a greater distance through the atmosphere before it reaches your eyes. During its travel, shorter- wavelength blue and violet wavelengths are preferentially scattered away, so the light that reaches your eyes consists mostly of red and orange hues.” ▪ In other words, if sunlight had to travel as long through the atmosphere during the day as it does during sunrise/sunset, then the Sun and sky would always be red! - What makes REALLY spectacular sunsets? o Mei scattering! - What makes clouds and the sky white/gray? o “Large particles associated with haze, fog, and cloud droplets scatter light more equally at all wavelengths. Because no color predominates over any other, the sky appears white or gray on days when large particles are abundant.” - Crepuscular Rays: “bands (or rays) of sunlight [...] These bright fan-shaped bands are most commonly seen when the Sun shines through a break in the clouds” --  these are caused by “Scattering of sunlight by haze, water droplets, or dust particles” - “Numerous small particles produce red sunsets, whereas large particles produce white (gray) skies. Thus, the bluer the sky, the less polluted the air.” 2.5 The Role of Gases in the Atmosphere - - The atmosphere is not an efficient absorber of the shortwave radiation that makes up most of the Sun’s energy, which means that the atmosphere is really heated by the Sun at all (oxygen and ozone pick up the UV, and water vapor gets a bit of the longer-wave stuff, but that’s about it) - On the other hand, the atmosphere is an efficient absorber of the longwave radiation that the Earth emits – especially the water vapor in the atmosphere – which means that the atmosphere gets practically all of its heat from the Earth o Atmospheric Window: the select window of wavelengths to which the atmosphere is transparent – in this case, 8-12 micrometers, where the Earth’s radiation is most intense. This has a cooling effect on the Earth, as “it allows longwave radiation from Earth’s surface to pass directly to space without being absorbed.”  o Clouds composed of tiny droplets of liquid water (not water vapor), however, block the atmospheric window: they absorb this longwave radiation and radiate it much of it back towards Earth’s surface, mitigating the window’s cooling effect - “Because the atmosphere is largely transparent to solar (shortwave) radiation but more absorptive of terrestrial (longwave) radiation, the atmosphere is heated from the ground up.” o Very important to the dynamics of weather o This is why the temperature drops as one gets higher in the troposphere: you’re further away from your radiator! - “Earth’s atmosphere “recycles” some of the outgoing radiation, which makes our planet habitable.” - Greenhouse Gases: “Gases that absorb longwave radiation” including water vapor, carbon dioxide o GREENHOUSE GASES ARE NOT CONSIDERED POLLUTANTS - Greenhouse Effect: The following process: “As Earth’s radiation heats these absorptive gases, the temperature of the atmosphere increases. The atmosphere, in turn, radiates some of this energy out to space, but more important, it radiates an equivalent amount back toward Earth’s surface, where it further warms the lower atmosphere.” o If not for this process, the Earth’s average temperature would be 0° F! Brr! ▪ THE GREENHOUSE EFFECT IS NOT A BAD THING!!!! ▪ WE WOULD NOT BE ALIVE WITHOUT IT!!!!!!! ▪ IT IS NOT THE SAME THING AS GLOBAL WARMING!!!!!!!!!! ▪ HUMAN ACTIVITY IS JUST COMPOUNDING THE EFFECTS OF AN OTHERWISE NATURAL PROCESS!!!!!!!!!!!!!!!!! o A positive feedback mechanism, amplifying the heat the Earth emits o Venus has an extreme version of this, with lots of greenhouse gases, which is why it’s so hot; the moon has no atmosphere and no greenhouse gases, so it's colder than Earth o Not actually much like a greenhouse at all, as greenhouses trap solar energy... which is precisely what the greenhouse effect doesn't do (it’s still a reasonable way to describe the trapping of energy within the system) 2.6 Earth’s Energy Budget - Even with fluctuations in hot and cold, the Earth’s average temperature is generally constant; this stability must mean there’s a balance between incoming and outcoming solar radiation and Earth radiation - “This surface-to-atmosphere equilibrium is accomplished through conduction, convection, and the transfer of latent heat as well as by the transmission of longwave radiation between the Earth’s surface and the atmosphere.” - Annual Energy Budget: “The annual balance of incoming and outgoing radiation, as well as the energy balance that exists between Earth’s surface and its atmosphere” - - Over time, Earth returns 100% of the energy it receives back into space “(minus small quantities of energy that become locked up in biomass that may eventually become fossil fuel)” - “A balance is maintained because all the energy absorbed by Earth’s surface is returned to the atmosphere and eventually radiated back to space.” - “The quantity of incoming solar radiation is, over time, balanced by the quantity of longwave radiation that is radiated back to space.” - There might be a balance of incoming and outgoing radiation over the whole planet, that balance is not maintained at each latitude - - Latitudes near the equator receive more radiation than they emit, and latitudes farther from the equator emit more radiation than they receive. This is why the equator is hot and the poles are cold  o This temperature difference remains stable (the equator is not constantly getting hotter, and the poles are not constantly getting colder) because winds and (to a lesser extent) the oceans are always trying to settle the imbalance by transferring heat from the equator to the poles o This constant energy transfer is what drives Earth’s weather system! o Areas where this transfer occurs, therefore, get stormier weather – which is over middle latitudes like 30° or 50° 9/13/24 Chapter 3: Temperature 3.1 For the Record: Air-Temperature Data - Daily Mean Temperature: “determined by averaging the 24 hourly readings or by adding the maximum and minimum temperatures for a 24-hour period and dividing by 2.” - Daily Temperature Range: “computed by finding the difference between” the maximum and the minimum - Monthly Mean Temperature: “calculated by adding together the daily means for each day of the month and dividing by the number of days in the month.” - Annual Mean Temperature: “an average of the 12 monthly means.” - Annual Temperature Range: “computed by finding the difference between the warmest and coldest monthly mean temperatures.” - Means are useful for making weather/climate comparisons between times or places - Ranges help show extremes, which is important for understanding weather/climate - Death Valley had the highest recorded temperature of anywhere on Earth – 134° F – and it regularly reaches the 120s otherwise. Why? It has the lowest elevation in the Western Hemisphere, it is a desert, mountains cut off the nearby ocean’s moisture and moderating effect, the skies are clear, and there’s no humidity to absorb sunlight - The Endicott Mountains in Alaska had the lowest recorded temperature in America – -80° F – due to its high latitude, high elevation, and lack of oceanic moderation - Isoline/Isotherm: “a line that connects points on a map that have the same temperature (iso = equal, therm = temperature). Therefore, all points through which [one] passes have identical temperatures for the time period indicated.” o (Isobars show the gradient of air pressure)  o Any interval may be used between isotherms, though 5° or 10° are the most common o Often, the temperature value of a given weather station won’t exactly equal the temeprature value of any isotherm, and so must have the relevant isotherms drawn on either side, estimated on how far away they are o o Isothermal maps, rather than labelling the isotherms themselves, can label the zones between them, marking them with the range of temperatures they encompass based on the isotherms on either side (for example, the zone between 20° and 30° would be labelled “20s”) o Temperature Gradient: “the amount of temperature change per unit of distance” ▪ Closely-spaced isotherms = high temperature gradient ▪ Widely-spaced isotherms = low temperature gradient o Isothermal maps turn many discrete points on a map into easily-identifiable patterns: min/max temperature and temperature gradient among them 3.2 Cycles of Air Temperature - Daily temperature cycle vs annual temperature cycle - Daily Temperature Cycle o Meteogram: “a graph that shows how meteorological variables changeover time” o On most days, temp minimums around sunrise and temp maximums around noon (of course, there are exceptions) o Earth’s daily rotation is the primary control of the daily temperature cycle, with a location getting sunlight for some amount of time before being moved into darkness o The Sun’s angle increases throughout the morning = the sunlight’s intensity increases. It peaks at noon and diminishes afterward o The atmosphere and Earth’s surface cool off at night, radiating heat back into space, until sunrise, at which point the Sun begins to heat Earth again (which is why the minimum is right before this happens) o o ^ At an equinox o As long as the amount of radiation received is greater than the amount of radiation lost, the temperature will rise – so, while the amount received is greatest at noon, the temperature reaches its peak right before the amount of radiation received stops being greater than the amount lost, which is later on (vice versa for the loss of temperature due to the amount of radiation lost being greater than the amount received) o Drier regions reach their maximum temperature later in the afternoon, while more humid regions reach their max earlier o "If temperature records for a station are examined for a period of several weeks, apparently random variations are seen. Such irregularities are caused primarily by the passage of atmospheric disturbances (weather systems) that are often accompanied by variable cloudiness and winds that bring air having contrasting temperatures. Under these circumstances, the maximum and minimum temperatures may occur at any time of the day or night.” o During the day, satellites capture visible light/solar radiation (color images); at night, satellites capture infrared radiation (black-and-white images)  o In cloudy areas, like NYC, it is hotter in the morning and cooler throughout the day: clouds keep warm, stale air in all night and convection cools it down - Annual Temperature Cycle o Generally speaking, temperature range increases the farther you are from the equator. The equator gets consistently warm temperatures all the time, while higher latitudes have more variety seasonal changes ▪ As a reflection of this, when looking at isotherms, the annual temperature gradient near the equator is much lower than the annual temperature gradient at higher latitudes o In the Northern Hemisphere, the most intense solar radiation is received on the summer solstice in June, and the least intense on the winter solstice in December – however, the hottest and coldest periods tend to occur in the following couple of months rather than on the solstice itself ▪ Why? It takes time for everything to heat up/cool down! ▪ The length of this lag can vary; in the US, the average is 27 days, while in regions close to a large body of water, the average is 36 days (and it can get longer than that) 3.3 Why Temperatures Vary - Temperature Control: “any factor that causes temperatures to vary.” - Earth’s primary temperature control is latitude, as it determines the Sun angle and length of daylight throughout the year - But it is not the only one! If it were, every location at a single latitude would have the same temperature – which they don’t - Elevation o In the troposphere, temperature decreases with height o Looking at two locations at the same latitude, the one with the higher elevation will have a lower mean temperature than the one with the lower elevation o Elevation also affects temperature range – the air thins as elevation increases, meaning less solar radiation is absorbed, reflected, and scattered; this increases the intensity of the solar radiation, making daytime heating more rapid – and likewise, nighttime cooling is also accelerated o Aside from the monthly temperature mean being lower, though, the annual temperature range is similar to one at a lower elevation - Land and Water o The heating of the Earth’s surface is the main factor heating the atmosphere o Different land surfaces absorb and reflect solar radiation in different ways (they have different albedos), thereby affecting atmospheric temperatures differently ▪ Differential heating of the Earth’s surface also creates areas of different air pressure o The biggest contrast in heating is between the land and the water o Land-surface heats and cools faster and to higher extremes than water- surface. Why? ▪ Because water is fluid and highly mobile, convection distributes heat through a larger mass, while the relatively static and solid land concentrates most of its heat where it is received, at the surface, as its only means of heat transferral is slow conduction. The land’s thin layer of heat can quickly cool down or heat up, while the water can store heat and move it around through convection, evening things out and thus requiring a higher amount of the water to change temperature for the total temperature to change significantly ▪ Because water has some transparency, allowing solar radiation to penetrate beyond the surface, while the land does not, with only the surface absorbing solar radiation ▪ Because water’s specific heat is over 3x that of land’s – so water needs more heat to increase in temperature than land Specific Heat: “the amount of heat needed to raise the temperature of 1 gram of a substance by 1°C” Heat Capacity: the amount of heat needed to raise the temperature of 1 gram of a substance by some amount of degrees (more general than specific heat) (Calorie: the amount of heat needed to raise the temperature of 1 gram of water (specifically) by 1°C) ▪ Because evaporation is greater from water bodies than from land surfaces – and evaporation is a cooling process, as energy used for evaporation does not serve to increase temperature o Hotspots occur over land ▪ (Temperature) Hotspot: Closed isotherm surrounding a small area with an extreme temperature, hot or cold; these move seasonally o “Collectively, these factors cause water to warm more slowly, store greater quantities of heat, and cool more slowly than land.”  ▪ Thus, locations near water have more moderate temperatures, while locations far or separated from water have more extreme temperatures ▪ As we’ll see with windward/leeward coasts, when the wind blows from continental regions to coastal regions, the latter will take on the more extreme temperature range of the former o Temperature variations between Northern and Southern Hemispheres: more water covers the Southern Hemisphere than the Northern, accounting for the smaller temperature range in the Southern Hemisphere ▪ The annual migration of isotherms is less dramatic in the Southern Hemisphere than in the Northern for the same reason (less land/water differential heating) o Unlike most bodies of water, the Mediterranean has some pretty extreme temperature changes; baffling; partly due to being mostly surrounded by land o ▪ Remember that the average ocean depth is 4km or 4000m ▪ Mixed layer from 0 to 80m depth ▪ Shallow thermocline between mixed and deep thermocline (if it is present; seasonal changes) ▪ Deep thermocline from 80m to 120m - Ocean Currents o Surface currents, like the Gulf Stream, are created by the wind: friction of the air on the water causes the water to move ▪ “major horizontal movements of surface waters are closely related to the circulation of the atmosphere.” ▪ These occur in the mixed layer of the ocean o The tropics get more solar radiation from the poles, and this excess heat is transferred from the former to the latter to keep their relative temperatues  stable (the tropics don’t keep getting hotter and the poles don’t keep getting colder) o This heat transfer is ¾ done by wind, ¼ by water o o Warm ocean currents move from the tropics towards the poles, whose most apparent impact is lessening winter cold at middle latitudes (the North Atlantic Drift, an extension of the Gulf Stream, brings warm water to much of western Europe, making their winters warmer than they would normally be at that latitude) o Cold ocean currents move from the poles toward the tropics, whose most apparent impact is lessening summer heat at middle latitudes and cooling the tropics (the Peru Current and California current bring cold water to the coasts of South America and southern California respectively, making their summers cooler than they would normally be at that latitude) o The movement of currents bends isotherms o The Antarctic circle polar current connects all of the ocean currents - Geographic Position and Prevailing Wind Direction o Wind flows from high pressure to low pressure o Prevailing Wind: a surface wind that blows predominantly from a certain direction ▪ Part of why New Yorkers hate New Jersey is because wind blows their pollution to us >:( o Windward Coast: “A coastal station where prevailing winds blow from the ocean onto the shore” ▪ Cooler summers and milder winters on account of the ocean having its full moderating effect o Leeward Coast: “a coastal location where prevailing winds blow from the land toward the ocean” ▪ Much larger temperature range on account of the ocean not moderating temperature  o Westerlies: “The prevailing winds in the midlatitudes [which] flow from west to east” ▪ Winds go east to west at the equator, west to east at midlatitudes o “If there is an ocean current along the coast, then the moderating effect of the ocean current can also be blown inland. Because of the prevailing westerly winds, the moderating effects of the North Atlantic Drift are carried far inland [in Europe].” o Mountains cut off the moderating effect of the ocean o Windward/Upslope Side: The side of a mountain facing towards the prevailing wind; tends to be cooler o Leeward/Downslope Side: The side of a mountain facing away from the prevailing wind; tends to be warmer ▪ The air coming down the mountain compresses as it descends, becoming warmer than when it started (due to adiabatic processes, which will be elaborated on later) - Albedo Variations o Albedo = reflectiveness – in other words, the higher something’s albedo is, the more solar energy it reflects back into space, preventing it from heating up Earth’s surface (and vice versa) - Cloud Cover o During the day: clear days are warmer than cloudy days, as clouds reduce the amount of incoming solar radiation and thereby reduce temperature; cloud albedo can vary from 25-90% o During the night: clear nights are colder than cloudy nights, as clouds absorb outgoing Earth radiation and emit some back to the surface, and thereby increase temperature o Overall, clouds decrease the temperature range by making days cooler and nights warmer o Extensive cloud cover can disrupt the typical seasonal cycle because of its temperature-reducing effect (for instance, if it’s stormy and cloudy throughout the summer, then the hottest part of the year will be the preceding spring) o Because the time scale of cloud movement is so rapid, they create uncertainty in weather reports – because at any moment a cloud (or clouds) can always come by... ▪ Time Scale: The amount of time it takes for a significant change to occur o NYC is usually very cloudy - Influence of Snow and Ice o Surfaces covered in snow/ice have a high albedo, and so reduce temperatures by reflecting solar radiation o Particularly significant is Arctic sea ice; it predictably expands in winter and contracts in summer, but it has been considerably shrinking since the 70s. This lowering of the Arctic’s albedo has lead to increasing temperatures in the region - Other Factors o The type of land surface: highly vegetated areas have cooler summers than other areas (on account of plants’ transpiration and shade) o Urban Heat Island: “a phenomenon in which the built environment alters a city’s air temperature. [...] Changes in the way cities absorb and emit radiation generally increase temperatures compared to surrounding rural areas.” ▪ Stone, steel, asphalt, concrete (materials of a city) absorb and store more solar radiation ▪ These surfaces are impermeable, causing greater runoff and thus a reduction in evaporation rate (and, as evaporation removes heat energy from an environment, this makes cities hotter) ▪ At night, the surfaces of the city, which have been storing heat energy accumulated in daylight, gradually release it, keeping the city aur warm ▪ Waste heat produced by vehicles, heating, air conditioning, power plants, factories, etc. ▪ Blanket of pollutants over the city performs the greenhouse effect and emits the heat the surface radiates back down ▪ “Not only are most cities heating up more rapidly than the planet— they tend to heat up at double the rate.” The surfaces of a city become much hotter than the air (on a hot day, asphalt can become blisteringly hot) ▪ The location of a city (in vegetated or arid land) has little impact on the urban heat island effect o Humidity also affects daily temperature range: water vapor absorbs and re- emits the heat the Earth’s surface radiates while cooling off at night, keeping the surface warmer (conversely, dry air causes the Earth to cool quickly at night, as the heat disappears into space)  o Atmospheric circulation patterns are also a big factor, moving warm and cold air across a region and influencing weather patterns (including cloud cover, which is a factor mentioned above) 3.4 Global Distribution of Temperature - - - Isotherms tend to follow latitude (as in, they lie horizontally and change as you go north or south) o This makes sense, as latitude is a major part of temperature - “because temperatures do not fluctuate as much over water as over land, the north–south migration of isotherms from January to July is greater over the continents than over the oceans.” o Likewise, the shift is greater in the Northern Hemisphere than in the Southern Hemisphere, as the former is covered by more land than the latter - Warm currents (moving from tropics to poles) push isotherms toward the poles, while cold currents (moving from poles to tropics) push isotherms toward the tropics  - - ^ Annual temperature range - Higher annual temperature range: o Higher latitude o Continental regions o Northern Hemisphere - Lower annual temperature range: o Closer to equator o Coastal regions o Southern Hemisphere 3.5 Temperature Measurement - Thermometer: “an instrument that measures temperature—either mechanically or electrically [...] To accurately measure airtemperature, [it] must be placed in the shade and mounted at 1.5 meters (5 feet) above the ground.” - Mechanical Thermometers o Liquid-in-glass Thermometer: “a bulb containing a fluid and a stem that has been bored to form a thin capillary tube” ▪ Heat causes the liquid to expand and rise up the tube; when it cools down, the liquid shrinks and returns to the bulb ▪ Meniscus: the curve of the end of the liquid thread in the tube; to measure the temperature, you compare the apex of this curve (whether it be convex or concave) with the thermometer’s scale o Maximum Thermometer: a mercury-in-glass thermometer which has a narrow passage – the constriction – just above the bulb; the mercury is forced through the constriction as it expands, but it is not able to easily able to return through it when temperatures fall, leaving the mercury lined up with the maximum temperature it had risen to (the thermometer is reset, with the mercury returning to the bulb, by shaking or whirling it)  o Minimum Thermometer: a low-density-liquid-in-glass (such as alcohol) thermometer, mounted horizontally, which contains a dumbbell-shaped index at the top of the liquid column; when temperatures drop, the index gets pulled toward the bulb with the liquid, but when it rises again, the liquid moves past the index, leaving the index lined up with minimum temperature the liquid had dropped it to (the thermometer is reset, with the index again sitting at the top of the liquid column, by tilting it) o Bimetal Strip: “two thin strips of metal that are bonded together and have widely different expansion properties. When the temperature changes, both metals expand or contract, but they do so unequally, causing the strips to curl. This change corresponds to the change in temperature.” - Electrical Thermometers o Thermistor/Digital Thermometer: a thermometer that " works on the concept that the flow of electricity through a metallic oxide disk or bead, called a resistor, is temperature dependent. As the temperature of the resistor changes, it alters the flow of electricity in a predictable way. Thus, an electric thermometer measures the flow of electricity and calibrates and displays that data as degrees of temperature.” ▪ Provides an instant reading in any temperature scale ▪ Used in the medical field, to measure vehicle oil temperature, in radiosondes, and in National Weather Service ground-level readings - “Accuracy depends not only on the design and quality of the instruments but also on where they are placed.” - The thermometer needs to be out of direct sunlight and away from heat-radiating surfaces (like buildings or the ground), and it must have sufficient air ventilation - Instrument Shelter: the ideal location for a thermometer, “a white [for high albedo] box with louvered sides to permit the free movement of air through it, while shielding the instruments from direct sunlight, heat from nearby objects, and precipitation [...] placed over grass whenever possible and as far away from buildings as circumstances permit [...] must conform to a standardized height so that the thermometers are mounted at 1.5 meters (5 feet) above the ground.” - Farenheit, Celsius/Centigrade, and Kelvin/absolute temperature scales  - - Celsius (°C): ice melts at 0°, water boils at 100° (difference of 100°) - Farenheit (°F): ice melts at 32°, water boils at 212° (difference of 180°) - Kelvin (°K): ice melts at 273°, water boils at 373° (difference of 100°; same scale as celsius, but numbers shifted) - Celsius to Farenheit:°𝐹 = 1.8(°𝐶) + 32 °𝐹 − 32 - Farenheit to Celsius:°𝐶 = 1.8 - Absolute Zero: 0° Kelvin, “the temperature at which all molecular motion is presumed to cease” (K has no negative temperatures, unlike C and F) 3.6 Applying Temperature Data - Heating Degree Days: an index of determining how much energy consumption is used for heating, assuming heating is only required when the outdoor daily mean temperature is 65° F or lower. A day’s heating degree days equals 65° F minus the outdoor daily mean temperature (if the outdoor daily mean is above 65°, the heating degree days equals zero). o I’ll abbreviate it to HDD cuz I feel like it o “Fuel consumption for a location can be estimated by calculating the total number of heating degrees for an entire year.” o “The amount of fuel required to maintain a certain temperature in a building is proportional to the total heating degree days.”  o One can imagine that colder places will have a higher total HDD than warmer places during the winter, as they need to spend more energy to reach the same warm temperature - o ^ Yeah. Hotter places spend more energy on cooling and colder places spend more energy on heating - Cooling Degree Days: an index of determining how much energy consumption is used for cooling, assuming cooling is only required when the outdoor daily mean temperature higher than 65° F. A day’s cooling degree days equals the outdoor daily mean temperature minus 65° F (if the outdoor daily mean is 65° or below, the cooling degree days equals zero). o CDD has the same principles as HDD; see above - Growing Degree Days: “The number of growing degree days for a particular crop on any day is the difference between the daily mean temperature and the base temperature of the crop, which is the minimum temperature required for it to grow.” o Used to approximate when a crop will be done growing – there's a number of total growing degree days a crop needs to be mature, and it should be ready to harvest by the time it reaches that number (doesn’t include other factors, like moisture or sunlight, but it’s useful nonetheless) - Apparent Temperature: “the perceived increase or decrease in temperature felt by the human body.” o Windchill, humidity, things that make it feel colder or hotter than the actual temperature - Heat Wave: “a prolonged period of abnormally hot and usually humid weather that typically lasts from a few days to several weeks. The impact [...] on individuals varies greatly, but it can be serious and even deadly.” o Worth noting that heat waves disproportionately affect people in poverty who can’t afford air conditioning o Cause more deaths on average than any other weather-related event, but they don’t get as much buzz as the others o Has the greatest impact in cities due to the urban heat island; the stagnant air of a heat wave also increases air pollution in cities o Climate change is likely to bring about more severe and more frequent heat waves - As the human body is constantly producing and emitting heat, anything that affects the rate of heat loss will affect our perception of temperature - Hot humid days are especially uncomfortable for people because the heat makes us sweat and the humidity prevents the sweat from being evaporated, which would cool us down o Heat Stress Index/Heat Index: an index “which combines temperature and to establish the degree of comfort or discomfort.” o o ^ The numbers in the colored boxes are the apparent temperature. Apparent temperature and heat stress increase as humidity increases ▪ Length of exposure to direct sunlight, wind speed, general health of the individual, and the bodily acclimation of the individual to such weather (if it rarely reaches that level of heat/humidity in your area,  your body will not be used to it and will not take it as well) also impact the level of stress the individual will experience - Windchill: “the perceived decrease in air temperature felt by the body due to the flow of air.” o Penetrates regular clothing, reduces the body’s retention of heat, rapidly chills exposed parts of the body, heightens cooling by evaporation, carries heat away from the body by replacing surrounding warm air with cold air o Windchill Temperature Index: an index “designed to calculate how the wind and cold feel on human skin [...] includes a frostbite indicator, which shows where temperature, wind speed, and exposure time produce frostbite.” o o ^ The numbers in the colored boxes are the apparent temperature. Apparent temperature and time until frostbite sets in decrease as wind speeds increase ▪ Age, physical condition, state of health, and level of activity (as well as clothing, obviously) also impact the level of discomfort the individual will experience 9/17/24 Lab Earth-Sun Geometry - https://www.earthspacelab.com/app/seasons/ 9/20/24 Chapter 4: Moisture and Atmospheric Stability 4.1 Water on Earth - >97% of Earth’s water is in the oceans; 100%) can occur, but in the lower atmosphere, the excess water vapor condenses into liquid water o o When taking a hot shower, the high temperature water has a high evaporation rate, adding water vapor to the air in the bathroom until the air is saturated and foggy  o Moisture enters the atmosphere primarily through the evaporation of ocean water, but plants, soil, and smaller bodies of water also play a role ▪ “the natural processes that add water vapor to the air generally do not operate at rates fast enough to cause saturation to occur directly” Unless it’s really cold out: then you’re able to see the hot moisture from your breath condense as you exhale it and promptly evaporate o TL;DR: + water vapor = + RH, - water vapor = - RH - Changes in Temperature: o In the hot shower e