Earth's Atmosphere: Structure and Contamination

• The atmosphere is Earth's smallest geological reservoir, making it vulnerable to contamination.
• The atmosphere's mixing time is rapid; debris from accidents can quickly spread globally.
• Contaminant spread in the ocean is slower, taking millions of years in other Earth reservoirs.

Atmosphere Definition

• A layer of gases surrounding a planet or material body held by gravity.
• Retention is more likely with high gravity and low atmospheric temperature.

Vertical Structure

• The troposphere is the layer nearest to Earth
• Temperature is highest near the surface and decreases with altitude.
• The average temperature gradient is 6.5°C per 1,000 m (3.6°F per 1,000 ft).
• Earth's surface heats the troposphere as rock, soil, and water absorb sunlight and radiate heat.
• Higher gravity and denser gases near the surface also contribute to higher temperatures.
• Warmer air beneath cooler air in the troposphere creates instability, causing mixing.
• All of the planet's weather takes place in the troposphere.

Temperature Inversion

• Air temperature increases with altitude, with warm air above cold air.
• Over land at night or in winter, cold ground cools the air above and forms inversions
• Near the coast, cold seawater cools the air, causing denser air to slide under warmer air inland.
• Temperature inversions are stable, trapping pollutants and causing unhealthy air conditions in cities.
• A thin layer at the troposphere's top has a temperature that does not change with height.
• Air from the troposphere and stratosphere rarely mix.

Stratosphere

• Temperature increases with altitude.
• Little mixing occurs between the troposphere and stratosphere, allowing materials to remain suspended for years.
• Pilots prefer flying in the lower stratosphere due to minimal air turbulence.
• The Sun is the direct heat source for the Stratosphere.
• Warm, less dense air sits above cooler, denser air, promoting stability and little air mixing.
• The ozone layer is located in the upper Stratosphere

Ozone Layer

• Located within the stratosphere at 15 to 30 km (9 to 19 miles) altitude.
• Its thickness varies by season and latitude.
• Ozone gas absorbs most of the Sun's harmful ultraviolet (UV) radiation, protecting life on Earth.
• Even with the existence of this layer, UVB radiation still reaches the surface.

Mesosphere

• Temperatures decrease with altitude.
• Because there are fewer gas molecules to absorb the Sun's radiation, heat source comes from the stratosphere below.
• Temperatures, especially towards the top, are extremely cold (approximately -90°C or -130°F).
• Air density is extremely low (99.9% of atmospheric mass is below).
• Very low air pressure.
• Without protection, an individual would experience severe burns from ultraviolet light.
• There is almost a complete lack of oxygen for breathing.
• The unprotected blood of a traveler would boil due to low pressure.
• Meteors burn in this layer.

Thermosphere

• The International Space Station (ISS) orbits the upper thermosphere at 320 to 380 km above Earth.

• Molecule density is so low that a gas molecule can travel approximately 1 km before colliding.

• Air feels very cold because of the lack of transferred energy.

• Solar radiation ionizes gas molecules, creating positively charged ions and negatively charged electrons in the ionosphere.

• Free electrons travel within the ionosphere as electric currents.

• Radio waves bounce off the ionosphere at night, enabling long-distance AM radio reception.

• Van Allen radiation belts are doughnut-shaped zones of highly charged particles, existing beyond the atmosphere in the magnetosphere.

• The solar wind carries particles from solar flares to Earth; trapped by Earth's magnetic field, they follow magnetic lines.

• Massive solar storms overload the Van Allen belts, causing auroras (nighttime aurora).

• Charged particles energize oxygen and nitrogen, emitting colored light.

Exosphere

• There is no true outer limit for the exosphere
• Gas molecules become very so scarce.
• Solar wind is beyond the atmosphere.
• Solar wind has high-speed particles (protons and electrons).

Atmospheric Composition

• Is a mix of several gases in differing amounts.
• Permanent gases include nitrogen (78%), oxygen (21%), and argon (0.9%).
• Trace gases include carbon dioxide, nitrous oxides, methane, and ozone.
• Water vapor concentration varies from 0-4% depending on location and time.
• Water vapor content is important in predicting weather.

Atmospheric Stability

• Measures the atmosphere's tendency to encourage motions.
• Vertical motion is tied to weather systems and their severity.
• In unstable conditions, lifted air parcels are warmer than surrounding air.
• Absolutely Unstable: The environmental lapse rate is greater than 9.8°C per kilometer
• Saturated or unsaturated parcels are warmer than the environment.
• Conditionally Unstable: The environmental lapse rate is between 4°C and 9.8°C per kilometer.
• Rising parcels become buoyant when saturated, depending on surface temperature and humidity.
• Absolutely Stable: The environmental lapse rate is less than 4°C per kilometer.
• Rising parcels are colder and sink.

Condensation

• The process by which water vapor in the air is changed into liquid water.
• Crucial for the water cycle and cloud formation.
• Clouds produce precipitation, returning water to Earth.
• The opposite of evaporation includes condensation nuclei like dust, carbon, and pollen.

Clouds

• Mass of small water droplets or ice crystals floating in the air.
• Form when air temperature is below the dew point.
• White in color because droplets and crystals scatter sunlight.
• Appear grey when blocking the sunlight.
• They are classified by shape and height.

High Clouds

• Made of ice crystals due to cold upper-sky air.
• 6000-18000m base in tropics; 3000-8000m in polar regions.

Cirrus Clouds

• Most common high cloud (5000-13000m).
• Composed of ice and consist of thin, wispy streamers (Mare's Tails).
• Typically white and predict fair weather.

Cirrostratus

• High cloud (5000-13000m).
• Thin clouds that cover the entire sky.
• The sun or moon can shine through.
• Sometimes a halo will appear around the sun or moon.
• Ice crystals refract light, creating haloes.
• Typically signals rain or snow in 12-24 hours, especially with middle clouds.

Cirrocumulus Clouds

• Small rounded puffs in long rows.
• Usually white, sometimes gray.
• Same size or smaller than the width of your littlest finger at arm's length.
• A mackerel sky appears if these clouds cover much of the sky.
• Usually seen in winter and indicate fair, cold weather.

Middle Clouds

• Altostratus and altocumulus clouds.
• Made of ice crystals and water droplets.
• 2000-8000m base in tropics; 2000-4000m in polar regions.

Altostratus

• Mostly covers the sky and appears grey or blue-gray.
• The sun or moon shine through, but appear watery or fuzzy.
• Usually forms ahead of storms with continuous rain or snow.
• A cloud becomes classified as a nimbostratus cloud if rain hits the ground.

Altocumulus

• They are grayish-white with one section of the cloud that is darker than the rest.
• Usually form in groups and are about 1 km thick.
• Thumb-sized at arm's length.
• Expect thunderstorms by late afternoon if seen in the morning on a warm, humid day.

Low Clouds

• Consist of water droplets.
• The base is from ground level to 2000m.

Stratus Clouds

• Uniform gray and can cover most or all of the sky.
• Looks like a fog that doesn't reach the ground.
• Can be associated with light mist or drizzle.

Stratocumulus Clouds

• Low cloud (surface-2000m) group.
• Low, lumpy, and gray.
• Look like cells under a microscope and line up in rows or spread out.
• Feature light precipitation, generally drizzle.
• Stratocumuls clouds look the size of your fist (distinguishes it from Altocumulus)

Nimbostratus

• Dark gray with a ragged base.
• Associated with continuous rain or snow.
• Sometimes cover the entire sky.

Clouds With Vertical Growth

• Cumulus and cumulonimbus clouds

• They grow high into the atmosphere and span all levels of the troposphere and can rise into the stratosphere.

• Develop by warm air rising from the surface.

• Cumulus and cumulonimbus clouds provide the some of the most interesting and severe weather on Earth.

Cumulus Clouds

• Puffy, white or light gray clouds that look like floating cotton balls.
• Have sharp outlines and a flat base.
• Approximately 1000m in base height and 1km meters in width.
• Can be is associated with good or bad weather.
• Cumulus humilis clouds are associated with fair weather.
• Cumulus congestus clouds are associated with bad weather.
• Tops look like cauliflower heads and mean light to heavy showers can occur.
• Cumulus cloud cells are about the size of a fist (or larger) at arm's length

Cumulonimbus

• Generally known as thunderstorm clouds.
• A cloud can grow to 10km high.
• High winds will flatten the top of the cloud into an anvil shape.
• Associated with heavy rain, snow, hail, lightning, and tornadoes.

Unusual Clouds

• They are: Lenticular, Kelvin-Helmholtz, Mammatus, and Contrails

Lenticular Clouds

• Form on the downwind side of mountains.
• Seemingly Stay in one place.
• Air moves up and over a mountain, and at the point where the air goes past the mountaintop, the cloud forms.

Kelvin-Helmholtz clouds

• Look like breaking waves in the ocean.
• Air continues flowing through mountains in a wave pattern.
• These clouds form when there is wind speed/direction differences.

Mammatus

• Pouches of clouds that hang underneath the base of a cloud.
• Usually seen cumulonimbus clouds that produce VERY STRONG STORMS.
• Described as looking like a field of tennis balls, melons, or breasts.
• Named after Latin word mamma (breast).

Contrails

• White streaks coming from high-flying jet airplanes .called condensation trails (contrails).

• Clouds formed.

• Water vapor condenses and freezes around exhaust particles.

• Source of water vapor is from the air around the plane and the exhaust.

• There are three types, Short-Lived, Persistent Non-Spreading, and Persistent Spreading

• Short-Lived: Air is somewhat moist, contrail forms right behind airplane.

• Persistent Non-Spreading: Air is moist, forms behind airplane; can stay for an extended time

• Persistent Spreading: This form will grow from the contrail

Solar Radiation and Earth's Energy Balance

• Earth's climate is solar powered.
• Earth absorbs 240 watts of solar power per square meter.
• Absorbed sunlight drives photosynthesis, evaporation, melts snow, and warms the system.
• Uneven solar radiation causes imbalances: The sun heats equatorial regions more than polar regions.
• The atmosphere and the ocean even out heating imbalances (Earth's heat engine)
• Earth's climate's heat engine must redistribute heat from and back to space.
• Earth's temperature doesn't infinitely rise because the surface/atmosphere radiate heat to space (Earth's energy budget).
• When incoming solar energy balances heat flow to space, Earth is in radiative equilibrium, stabilizing global temperature.

Topics to be covered

• Earth radiation budget
• Physics of radiative heat transfer.
• Effects of earth's spherical shape and the orbit through weather.
• Earth's vital statistics

Climate

• Typical weather state at a particular location and time.
• Encompasses variables mean, temperature, humidity, windiness, cloudiness, precipitation, visibility.
• The state of Earth's habitable environment involves the atmosphere, hydrosphere, land masses, cryosphere, and biota:
  • Atmosphere: The fast-responding medium.
  • Hydrosphere: Water in liquid form.
  • Land Masses: Affect the atmosphere flow
  • Cryosphere: Ice component of systems
  • Biota: Forms of Life

Energy From The Sun

• Drives the climate system, absorbed and converted to heat, which warms the planet.
• Solar radiation absorption is uneven in space and time, is what gives rise to climate patterns.

The Sun

• Star at the center of our Solar system, of mostly hydrogen and helium.
• Thermonuclear fusion reaction makes sun.
• Solar heat energy goes as electromagnetic waves i.e Radiation.
• Solar radiation occurs across wavelengths
• Solar radiation centers on the 0.2-2 micrometers range.
• This main range includes ultraviolet (UV, 0.001-0.4 µm), visible radiation (light, 0.4-0.7 µm), and infrared radiation (IR, 0.7-100 μm).

Radiative Heat Transfer

• Independent of matter; can move heat in empty space.
• Bodies emit radiation; wavelength and energy are determined solely by temperature.
• Energy flux drops with the square of emitting body distance.
• Radiation changes when contacting objects, transfers heat.

Radiation Transfer From Sun To Earth: Properties of Solar Radiation

• Sun is 150 X 106 kilometers from Earth.

• A surface temperature of 5780 K (DEGREES KELVIN = DEGREES C + 273.15)

• The energy flux at the surface of the Sun is approximately 63 X 106 W/M2 which is at the center of the visible part of the spectrum.

• Spectral properties stay consistent, but flux decreases over distance.

• Radiative flux is approximately 1360 W/M2 at the outer limit of the Earth’s atmosphere.

• The sun being located at one foci is what makes the earth elliptical.

• The earth is closer at time of year (PERIHELION)

• The "opposite" is APHELION.

• The greatest point of radiation is the true equator

• 0.3 of the surface that reflects

Effect of Orbits shape

• Radiation at the top of the atmosphere varies by 3.5% yearly.
• Earth's orbit is elliptical, with the Sun at one focus.
• Perihelion: Earth is closer to the Sun.
• Aphelion: Earth is farthest from the Sun.
• Perihelion's time varies, with a 21,000-year cycle.
• Perihelion happens mid-winter for the Northern Hemisphere currently.

Effect of Earth's Spherical Shape

• If a Disk the radiation would be equal
• Earths rays isn't equal since it's a sphere.

Axis Tilt and Seasons

• If the axis was perpendicular, the energy flux would decrease along with cosine latitude.
• But the axis tilts at 23.5°.
• Summer Solstice: North Pole points at the Sun, and South Pole is hidden.
• Winter Solstice: North Pole points away, with sunlight from the South, and South Pole receiving sunlight..
• Solstices has perpendicular radiation at the latitude Cancer or Capricorn.
• Spring/Fall Equinox: The axis tilts parallel
• Amount of radiation varies.

The Earths's Albedo

• Reflect sunlight to the moon.
• Clouds are good.

General Circulation

• Bodies of water influence temperature
• Bodies of water and land cool differently
• Small scale circulation is called Sea Breeze
• Mountain regions are called mountain/valley breeze.

Temperature

• Measurement of hot or coldness.
• Several scales exist: Celsius, Fahrenheit, and Kelvin
• COLD is absolute zero, measure to make a object is zero kelvin.

Geographical Tempretures

• Land/ocean distribution determines temperature.
• Latitude influences the received solar radiation.
• Higher latitude influences the angle of incidence and duration of day length
• Land surfaces behave differently from water surfaces due to specific heat.

Land and water Surfaces

• Solar radiation warms water, is heater.
• Water is mixed with energy
• Evaporating removes heat