Introduction to Physical Geography Study Guide PDF

Introduction to Physical Geography (GEOG1) Lecture 1: Introduction to Physical Geography ​ Physical Geography: The study of spatial and temporal patterns of Earth's physical environment, including energy, air, water, weather & climate, landforms, soils, animals & plants, & the Earth...

Introduction to Physical Geography (GEOG1) Lecture 1: Introduction to Physical Geography ​ Physical Geography: The study of spatial and temporal patterns of Earth's physical environment, including energy, air, water, weather & climate, landforms, soils, animals & plants, & the Earth itself ​ The Four 'Spheres' (Earth’s Subsystems): ○​ Lithosphere: The solid Earth, including mountains, soils, tectonic plates, volcanoes, and faults. ○​ Atmosphere: Weather, climate, greenhouse gases, aerosols, and water in its various forms. ○​ Hydrosphere: Oceans, rivers, lakes, streams, glaciers, snow, and ice. ○​ Biosphere: All living things (plants, animals, bacteria, humans, carbon, and agriculture). ​ Interactions Between the Spheres: ○​ Volcanic eruptions (lithosphere) impact atmospheric chemistry, temperature, and precipitation (atmosphere & hydrosphere). ○​ Climate changes can affect ecosystems and biodiversity (biosphere). ○​ Water cycles shape landscapes and influence climate patterns (hydrosphere & lithosphere). ​ The Role of Water in Geography: shapes Landscapes, Influences life distribution, climate regulation ​ Alexander von Humboldt (1769–1859): Mapped climate and vegetation across different regions, developed early theories explaining Earth’s physical variations. ​ Latitude – Measures distance north or south from the Equator. ​ Longitude – Measures distance east or west from the Prime Meridian. ​ Hemispheres: divided into Northern, Southern, Eastern, and Western Hemispheres. ​ Great Circles: the shortest distance between two points on Earth follows a great circle path. Lecture 2: Spherical Earth, Solar Energy, and the Seasons: ​ The sun is Earth’s primary source of energy, shaping the climate and physical environment. ​ Energy is a property of every physical system, including matter (anything that has mass and occupies space). ​ The energy that the sun provides the earth comes in the form of Electromagnetic Radiation. ○​ The Sun generates huge amounts of energy due to a continuous nuclear reaction that occurs in its interior, a process by which lighter elements (Hydrogen) combine to form heavier elements (Helium), and the excess energy is released ○​ Photons leave the sun (and all other objects) and travel through space in waves at the speed of light ​ The Sun is located about 150 million kilometers (~90 million miles) from the Earth at the center of our Solar System ​ Joule (J): 1 J = the energy required to lift a small 100g apple vertically 1 meter. ​ Watt (W): 1 W = 1 J per second. This is the RATE (“flux”) of energy entering or leaving a system ​ Why are the poles colder than the equator? ○​ The equator receives more direct sunlight, while polar regions receive sunlight at a lower angle, spreading the energy over a larger area (solar radiation = less intense) ​ Solar altitude angle: the angle between the sun and the horizon (where you see the sun in the sky) ○​ Higher latitude= smaller solar angle because sun is on horizon ○​ A higher Solar Altitude Angle means more direct sunlight and higher temperatures. ​ The Plane of the Ecliptic: all planets in our Solar System revolve counter-clockwise around the sun the same plane ​ Earth’s axis is tilted 23.5° off from being perpendicular to the plane of the ecliptic ​ Why does Earth’s tilt cause the seasons? ○​ The tilt changes how directly sunlight hits different parts of the planet throughout the year. ​ June 21-22: Summer Solstice in the Northern Hemisphere (longest day, sun over 23.5°N, start of summer); Winter Solstice in the Southern Hemisphere (shortest day, colder temps, start of winter). ​ December 21-22: Winter Solstice in the Northern Hemisphere (shortest day, sun over 23.5°S, start of winter); Summer Solstice in the Southern Hemisphere (longest day, warmer temps, start of summer). ​ March 21-22: Spring Equinox in the Northern Hemisphere, Autumn Equinox in the Southern Hemisphere (equal day/night, sun over Equator, seasonal transition). ​ September 21-22: Autumn Equinox in the Northern Hemisphere, Spring Equinox in the Southern Hemisphere (equal day/night, sun over Equator, seasonal transition). ​ Why is winter colder than summer? ○​ In winter, the sun’s rays hit at a lower angle, spreading the energy over a larger area and reducing heat intensity. During summer, sun gets higher in the sky, solar angle is larger, solar energy is more concentrated = warmer ​ Which latitude has the highest solar altitude angle on the Northern Hemisphere Summer Solstice? ○​ 23.5°N b/c 90° solar angle ​ Solar Declination Latitude: The latitude where the sun is directly overhead at noon on a given day. ​ December 21-22: Northern Hemisphere Winter Solstice/ Southern Hemisphere Summer Solstice ○​ Solar declination latitude = 23.5°S ○​ 66.5°S: Antarctic Circle ​ June 21-22: Northern Hemisphere Summer Solstice/ Southern Hemisphere Winter Solstice ○​ Solar declination latitude = 23.5°N  ○​ 66.N°S: Artic Circle ​ Tropics: (23.5°N to 23.5°S) receive the most intense solar radiation year-round. ​ Why does the North Pole receive the most solar radiation on the planet during June? ○​ The North Pole experiences 24 hours of daylight, maximizing solar input= more photons in any given day of the poles on the summer solstice ​ What latitude would you need to travel north or south to see 24 hours of sunlight on the Summer Solstice? ○​ 66.5°N (Arctic Circle) or 66.5°S (Antarctic Circle) ​ Permafrost: permanently frozen ground ○​ Low solar altitude angle and low solar intensity in the Arctic → cold condition → Frozen soil ○​ Important b/c soils in Arctic is carbon rich (stored carbon because Frozen) → releases carbon Lecture 3: Earth’s Energy Balance, the Greenhouse Effect, and Global Warming ​ The Electromagnetic Spectrum: ○​ Shortwave= most intense ○​ Longwave = least intense ​ Photons travel at speed of light through waves ​ Wavelength: The distance between two waves of electromagnetic radiation (measured in micrometers (μm)) ​ We can only see a few wavelengths ​ Objects need to be extremely hot to emit electromagnetic radiation that is in the visible part of the spectrum ​ Everything emits electromagnetic radiation ​ Rule #1: The hotter an object, the shorter the wavelengths it emits. ​ Rule #2: The shorter the wavelengths, the more *intense* the radiation ​ The sun emits shortwave radiation (visible light, ultraviolet), while Earth emits longwave radiation (infrared). ​ How do we know that this person is *reflecting* the visible light and *emitting* the infrared light? ○​ The person reflects visible light from an external source, making them visible in the left image. In the infrared image, they emit infrared radiation due to body heat, appearing bright. The trash bag is transparent to photons that are in the infrared portion of the spectrum. The glasses are okay to infrared light but transparent to visible light. ○​ A human body emits infrared radiation but only reflects visible light. ​ Applies to greenhouse gases ​ Movement from atoms warmer=faster the atoms are vibrating ​ If the earth is constantly being bombarded by solar radiation, why does it not heat up indefinitely? ○​ Because it emits energy (longwave radiation) back into outer space to remain at an equibiurm temperature ​ To maintain stable temperature, the earth must send radiation to outer space as fast as it comes in. ○​ Rate of photons receiving = rate of photons exiting. if not, temperature will change ○​ Shortwave radiation reflected to outer space ○​ Long wave radiation admitted to outer space ​ Radiative equilibrium: The amount of solar (shortwave) radiation entering earth’s atmosphere must be equaled by the amount of radiation sent back to outer space (reflection + longwave emission) in order for earth to maintain a stable temperature. ○​ Solar (shortwave) radiation entering the atmosphere = Longwave radiation emitted by Earth + Shortwave reflected to space ○​ Done in two ways: ​ Solar radiation is reflected off a surface. ​ The rest is absorbed into Earth and emits long wave radiation back to outer space ​ Emission: objects can emit energy away by sending photons outward. This is a way to lose energy and cool. ​ Reflection: objects can reflect (bounce) photons away without absorbing. The energy status and thus temperature of the object is unaffected. ​ Absorption: objects can absorb photons. This increases the energy status of the object and therefore increases the temperature. ​ Albedo: The fraction of incoming solar radiation that is reflected back into space. ○​ High albedo = More reflection (e.g., ice, snow). ○​ Low albedo = More absorption (e.g., oceans, forests). ○​ Earth’s average planetary albedo is ~30%, meaning 30% of sunlight is reflected back into space. ​ What happens to the other ~70% of solar radiation that enters Earth’s atmosphere? ○​ It is absorbed by the surface and atmosphere and later emitted as longwave radiation. ​ Incoming solar at top of atmosphere (342 W/m^2)- reflected solar back to space [0.30(342 W/m2)]= Longwave radiation the earth must emit to outer space in order to maintain a stable temperature (239 W/m2) ​ What are some parts of the globe with especially high albedos? Low albedos? ○​ High albedo: Ice caps, deserts, clouds, poles ○​ Low albedo: Oceans, forests, dark surfaces. ​ What is the main cause of geographic differences in the amount of radiation emitted by earth’s surface? ○​ Temperature: cold=less intense radiation (less longwave radiation + longer waves). Hotter= more long wave radiation because has to emit long wave radiation to cool off ​ Earth emits much more longwave radiation from its surface than it ultimately emits to outer space. WHY? ○​ Because of greenhouse effect: atmosphere is “transparent” for short wave radiation but opaque for long wave radiation  ​ Greenhouse effect: most of outgoing longwave radiation is absorbed by greenhouse gas molecules and re-emitted in all directions, warming the surface and lower atmosphere ○​ The sun's shortwave radiation passes through the atmosphere and heats the Earth's surface. ○​ The Earth emits longwave radiation upward. ○​ Greenhouse gases” in the atmosphere absorb much of the longwave radiation that earth’s surface emits toward outer space, which heats the atmosphere ○​ The greenhouse gases then re-emit longwave radiation, sending some downward and some to space. This slows the rate at which earth can cool off by emitting longwave radiation to space ○​ Bombardment from downward longwave radiation causes earth’s surface to warm. Warming, in turn, causes earths’ surface to emit more longwave radiation upwards (hotter objects emit more radiation). ○​ As longwave emission from earth’s warming surface continues to increase, more longwave radiation can escape to space despite the fact that most radiation emitted from the surface continues to be absorbed by greenhouse gases. Once radiative equilibrium is achieved, warming stop ​ Without the Greenhouse Effect, Earth’s temperature would be: ~ -15°C (5°F) (much too cold for human life). ○​ Instead, the Greenhouse Effect keeps it at ~18°C (65°F), making life possible. ​ 1850s: John Tyndall’s experiment to detect heat-trapping effects of gases ​ Greenhouse gases: ○​ Water Vapor (H₂O): The most abundant greenhouse gas. ○​ Carbon Dioxide (CO₂): Major contributor to human-caused global warming. ○​ Methane (CH₄): More powerful than CO₂ but present in smaller amounts. ○​ Ozone (O₃): Absorbs UV radiation and also acts as a greenhouse gas. ​ How does the greenhouse effect work? ○​ The ability of a gas molecule to absorb electromagnetic radiation, and the wavelength of radiation absorbed, depend on the frequency at which the molecule vibrates. Some molecules can vibrate in multiple directions and frequencies, making them very good absorbers longwave radiation ​ But humans are rapidly increasing the greenhouse gas concentration. ○​ Humans pull carbon out of Earths crust and burning for energy Lecture 4: Water, Latent Heat, Specific Heat, and Local Energy Balances ​ Net Radiation (Rnet): The rate of incoming radiation minus the rate of outgoing radiation (watts per square meter, W/m²). ○​ Needs to be zero to be at equilibrium ○​ Earths is close to zero, but not because of green house gases ○​ Poles = constant negative net radiation ​ Rnet at the earth’s surface is very positive (+106 W/m²) because the surface absorbs much more radiation than it emits. ​ How does Earth’s surface get rid of all this excess energy?  ○​ Evaporation, latent heat flux, and sensible heat flux move energy into the atmosphere. ​ Why doesn’t this pot of water heat up indefinitely? ○​ Net radiation at the bottom of the pot is very positive, but evaporation carries energy away, cooling the surface. ​ Evaporation requires energy from the surrounding environment. ○​ When evaporation occurs, the energy that caused the evaporation is carried away by water vapor molecules ○​ Because energy is required to convert liquid water into water vapor, energy is transferred from the site of evaporation to the water vapor molecules that float into the atmosphere. This COOLS the evaporation site ​ Latent Energy: The energy stored in water vapor molecules/ energy associated with water phase change ○​ Water phase change requires A LOT of energy ​ Hydrogen bonding: An attraction between water molecules that makes the molecules want to stick together. This makes it difficult to raise the temperature of liquid water ​ Specific Heat of liquid water: The energy required to heat 1 kg by 1 °C: 4186 J/(kg x °C) ​ Why are latent heat fluxes so high over the ocean? ○​ Oceans provide a continuous water source for evaporation, transferring large amounts of energy to the atmosphere. ​ Where do you expect latent heat fluxes to be lowest and why? ○​ Over dry land (e.g., deserts) because there is little water available for evaporation. ​ What time of year are latent heat fluxes the highest and why? ○​ They are the highest in the summer because that's when the solar energy is the most intense ​ Just as evaporation causes cooling, condensation causes warming. ​ Condensation: when water vapor molecules turn back into the liquid phase ○​ releases energy into the atmosphere, causing warming and wind. ​ Sensible Heat Flux: Exchange of energy through direct contact between two things of differing temperatures. ​ Sensible heat flux, on average, moves energy (heat) from surface to atmosphere. Why? ○​ Because it depends on temperature differences and there is a large temperature difference between the surface and atmosphere. ​ Why are upward sensible heat fluxes generally higher over continents than the ocean? ○​ It is hard to change the temperature of the ocean. If you put energy on the surface, that will go to evaporation, which causes cooling. ​ What time of year are upward sensible heat fluxes the most positive? ○​ Summertime because the surface is hotter. ​ What is happening when the upward sensible heat flux is negative?  ○​ heat is being transferred from the atmosphere to the surface, rather than from the surface to the atmosphere. This occurs when the surface is cooler than the air above it, causing a downward heat transfer. ​ Energetic balance: rate of incoming energy equals rate of outgoing energy ○​ For a planet, radiative equilibrium is necessary because the planet cannot exchange energy with outer space via water molecules or direct contact. ○​ For the Earth’s surface, energetic balance can be achieved with more than just radiation fluxes. ​ Shortwave absorbed = Longwave emitted + Upward latent heat flux + Upward sensible heat flux. ​ What is evaporation? ○​ The transition of a liquid to a gas (vapor) ​ Evaporation: As a liquid water molecule warms (gains energy), it starts vibrating faster, which allows it to distance itself from other liquid water molecules. If a fast-moving molecule is exposed to the atmosphere, it may escape its bonds to other liquid molecules entirely and become vapor. ○​ Vapor phase: more energy per molecule, molecules are moving fast. ○​ Liquid phase: less energy per molecule, molecules are moving slow ​ Phase change occur above surface ​ What is condensation? ○​ The transition of a gas (vapor) to a liquid. ​ Condensation: As a water vapor molecule cools (loses energy), it starts vibrating more slowly, which makes it more likely to spend time near other vapor or liquid water molecules and hydrogen bonding can occur, causing the molecules to congeal (liquify) ​ If condensation exceeds evaporation, there is net condensation. ○​ The air is saturated. ​ If evaporation exceeds condensation, there is net evaporation. ○​ The air is not saturated. ​ Specific Humidity: The fraction of an air mass’s mass that is water vapor (kg of H₂O vapor per kg of air). ​ Vapor Pressure: The contribution of water vapor to atmospheric pressure (measured in hectopascals, hPa). ​ What needs to happen for evaporation from a water surface to increase? 1)​ Add energy (heat) to the water molecules, causing them to speed up and be more likely to be in the vapor phase and less likely to settle into the liquid phase. a)​ Water/liquid + occurring faster than condensation, water vapor will accumulate in the atmosphere, role of condensation equals increase, concentration of water vapor increase (saturated) 2)​ Reduce the concentration of water vapor molecules (reduce the vapor pressure) above the liquid’s surface. ​ Saturation Vapor Pressure: The vapor pressure at which air becomes saturated, meaning that evaporation rate can no longer exceed condensation rate. Units: hectopascals (hPa), which is a unit of pressure The warmer the air, the higher the saturation vapor pressure.  ​ This is why warmer air can “hold” more water vapor than cooler air ○​ This response of saturation vapor pressure to temperature is known as the Clausius-Clapeyron relationship ○​ The exponential shape means that as air temperature rises, the amount of water vapor that the air can accommodate rises exponentially ​ Relative Humidity: The amount of water vapor in the air expressed as a percentage of the amount needed for saturation at a given temperature (%) ​ Dew Point: The temperature at which air with a given specific humidity becomes saturated (°C) ​ Why is the dew point temperature generally lower over continents than over neighboring ocean areas? ○​ Oceans provide unlimited supply of water constantly have water vapor flexing into atmosphere for evaporation, more water vapor in atmosphere →higher dew point= less need to cool air to saturate ○​ Land = water not constant & air is below saturation, less water vapor= lower dew points ​ What are the two ways to bring air closer to saturation? 1)​ Cool air, closer to saturation vapor pressure 2)​ Adding humidity ​ What is the relative humidity if the vapor pressure increases and/or the temperature decreases such that the saturation vapor pressure is reached? ○​ If the vapor pressure increases and/or the temperature decreases to the point where the saturation vapor pressure is reached, the relative humidity becomes 100%, meaning the air is saturated. ​ Mixing of air of differing temperatures is a great way to create fog. ○​ The warm air of our breath and cold air outside causes supersaturation for a few seconds which is the fog that comes when you breathe at night. ​ As temperature rises, saturation vapor pressure increases, and the atmosphere’s capacity to carry more water vapor increases. How should this affect the global water vapor content of the atmosphere? ○​ On average globally, as we warm the atmosphere the amount of water vapor in the atmosphere increases. ​ More water vapor in the atmosphere means that when atmospheric conditions allow for a storm, the storm will tend to be heavier. ​ Even though water is necessary for life, too much water can be disastrous. ○​ Increasing intensity of heavy storms may enhance flood risk globally.  ○​ Sea wall overtopped = flooding Lecture 5: Atmospheric Convection, Sea Breeze, and the ITCZ: ​ Vertical Structure of the Atmosphere ○​ Troposphere (~80-85% of atmosphere’s mass) ○​ Stratosphere (~15-20% of atmosphere’s mass) ○​ Mesosphere (