Atmospheric and Oceanic Science 100 Final Exam Review Weather Discussion: -Visible Satellite Image: Space is black (very cold) Low Clouds: brighter, because they?re warmer High Clouds: darker, because they?re colder -Infrared Satellite Image: Space is white (very cold) Low Clouds: darker, because they?re warmer High Clouds: brighter, because they?re colder -Weather Station Models: Temperature: depicted by top number on left side, should always be higher or equal to dew point temperature, actually depicts Kinetic energy Dew Point Temperature: depicted by bottom number on left side, expresses amount of moisture in the air Wind Direction: depicted by bar stemming out of center icon, expresses where the wind is coming from Wind Speed: depicted by slashes stemming off of the wind direction bar Each short bar represents about 5 mph of wind One Long Bar is two times as long as the short bar, meaning each long bar represents 10 mph of wind One flag represents 50 mph of wind Cloud Cover: depicted by the center circle If none of the circle is filled, clear skies 25% filled, few clouds 50% filled, scattered clouds 75% filled, broken clouds 100% filled, overcast Basic Symbols: located in between the temperature and dew point Fog: Two parallel lings Rain: dots 2 dots: light 3 dots: moderate 4 dots: heavy Haze: Infinity symbol Thunderstorm: Atmospheric Structure and Composition: -Composition of Earth?s Atmosphere: Nitrogen: 78.08% of earth?s atmosphere Source: Denitrification during decay of biological matter, volcano eruptions Sink: Source of energy for N-Fixing organisms (plants) Oxygen: 20.95% of earth?s atmosphere Essential for earth?s atmosphere Source: Photosynthesis Sink: Oxidation, decomposition, respiration Helium, Hydrogen: .00056% Composed early atmosphere Since it?s so light, it escapes earth?s gravitational pull, which is way, although there was so much before, there is very little now Water Vapor: Most important greenhouse gas Has large impact on weather Exists on earth as a gas, liquid, and solid It?s concentration is variable in earth?s atmosphere Tropical Regions: 4% Polar regions: 0% Carbon Dioxide: .037% Second most important greenhouse gas Source: Vegetation decay, fossil fuel combustion, deforestation, volcanoes Sink: Photosynthesis, dissolves into oceans, weathering on longtime scale Carbon dioxide concentration is steadily increasing due to anthropogenic fossil fuel combustion Carbon dioxide Concentrations are higher in winter and lower in summer due to photosynthesis Methane: .00017% Concentration has doubled since Industrial revolution Source: Cows, rice paddies, coal mining Nitrous Oxide: Source: soil denitrification, fertilizers Ozone: .000004% Major source of heating stratosphere Absorbs UV rays before they reach surface, which heats stratosphere Since UV rays are harmful, before ozone was present in the atmosphere, life could only exist in the oceans Source: photochemical reactions Sink: destruction in the atmosphere Aerosols: Dust, soot, salt Particles that are suspended in the air Cloud Condensation Nuclei Aid in cloud formation Without aerosols, there would be no clouds -Origin of the Atmosphere: Big Bang Theory Universe, approximately 10-20 billion years ago Mostly composed of He, H and Li Heavier elements were found in supernova explosion Atmosphere 1 Origin of solar system, approximately 4.7 billion years ago Earth formed through collisions of dust, rock, planetesimals, planets (in that order) Atmosphere 2 Volcanic outgassing Composed of carbon dioxide, 10%, water, 80%, Nitrogen, 2% and small traces of others Earth cooled forming Water Vapor, forming clouds Clouds brought precipitation, which brought oceans, glaciers and lakes Carbon Dioxide dissolved into oceans and deposited at the ocean floor Atmosphere 3 Origin of life, approximately 3.9 billion years ago Cyanobacteria evolves in ocean (Green blue algae, first form of life on earth) Begins photosynthesis which produces oxygen Oxygen in the atmosphere allows ozone to form Ozone blocks harmful UV rays, which allows life to form on the surface Sexual Reproduction 1.5 billion years ago Aerobic and anaerobic bacteria form symbiotic relationship Yields mitochondria eukaryotes Approximately 0.5-1 billion years ago sexual reproduction occurs Sharing of chromosomes begins, evolution occurs Plants at surface form -Vertical Structure of Atmosphere Red Line Depicts temperature Troposphere: Temp. decreases with altitude All weather occurs here 80% of earth?s mass located here Tropopause: Upper lid on weather patterns Height is function of latitude Higher near equator Lower in polar regions Stratosphere: Temperature increases w/ altitude Because ozone molecules, near the top of stratosphere, absorbs UV rays Mesosphere: Temperature decreases with altitude Thermosphere: Temperature increase with altitude -Other Key Notes: Density=mass/volume Warmer air is less dense than cooler air Pressure=force/area Pressure supports the weight of the air above a given level Density and pressure decrease with altitude Ideal Gas law: PV=nRT Energy, Temperature and Heat: - Energy: capacity to do work, energy is always conserved, Total Energy=PE+KE Kinetic energy: energy of motion KE=½mv2 Examples: falling rain drop, heat energy Potential energy: potential to do work PE=mgh Examples: Reservoir behind a dam Latent Heat: the heat required for a substance to change phase Heat is required when a substance converts to a less ordered state Heat is released when a substance converts to a more ordered state -Temperature and its relation to energy Temperature is actually a measure of average kinetic energy -Heat Transfer in the Atmosphere Conduction: heat transfer from molecule to molecule Heat flows from warm to cool Conductivity: rate of heat transfer by conduction Convection: vertical transfer of heat Convection is strong over deserts(sands give off heat to cool air above) Insufficient in poles where surface is cold Advection: horizontal transfer of heat Cooler air blown by the wind horizontally, cools warmer air Radiation: energy transfer by electromagnetic waves Example: solar radiation Radiation and Temperature: According to the Stefan Boltzmann Law, warmer objects emit more radiation than colder objects According to Wien?s law warmer objects have maximum emissions at shorter wavelength Solar Radiation: Scattering: molecules reflect radiation and radiation scatters Reflection: molecules reflect radiation Albedo=(amount of reflected radiation/amount of total radiation)x100% -Absorption and Emission: -The Greenhouse Effect: caused by selective nature of radiative absorption in the atmosphere Absorption Spectra: indicates the percent absorption at a given wavelength (depicted above) Atmospheric Window: region of spectrum between 8-11 micrometers Allows earth to cool because IR wavelengths are not absorbed, thus IR waves can escape into space Important Greenhouse gases: Carbon Dioxide and Water Vapor absorb long wave radiation, heating the atmosphere So, and increase in either gas will increase absorption, global temperatures Methane, Ozone, and Oxygen are also very important Atmosphere is transparent at .3-.7 micrometers, which is visible light Radiation and Satellite Imagery Infrared Imagery measures radiation, the warmer the clouds, the more radiation it will emit This means there is a larger greenhouse gas effect Seasonal and Diurnal Cycles, Local Temperature Variations -Geometry of Earth?s Orbit: Elliptical Orbit, sun being the foci of the orbit Perihelion: point when earth is closest to sun, at this point in time, the perihelion is approximately January 3rd Aphelion: point when earth is farthest from sun, at this point in time, the aphelion is approximately July 4th Earth rotates on an axis of about 23.5 degrees (Obliquity) Tilt determines seasons, the distance from the sun does not Angle of Incidence: measures the angle at which sunlight hits the earth?s surface Sunlight hitting the surface on an angle takes a longer path through the atmosphere, making it cooler due to: More sunlight being absorbed or scattered Sunlight hitting the surface directly is more powerful because it is concentrated on a smaller area Length of day: summer days are longer than winter days because of the tilt as well This also means that summer will be warmer than winter because there will be more time for the earth to absorb sunlight -Heat Capacity: the ability for one gram of a given substance to increase by one degree Celsius, although most sun comes at noon, its hotter in the early afternoon because most sun is absorbed Scattering/Albedo: not all sun will reach the surface Heat transport: radiation must be converted Elevation: temperature decreases with height in the troposphere Surface type: surface with lower heat capacities heat quicker Sand has a very low heat capacity, deserts are very hot Vegetation has a higher heat capacity Water has a high heat capacity and acts as a stabilizer of temperature Areas of land near water don?t fluctuate in temperature as much Clouds reflect a lot of radiation Less radiation flows to the surface, but more radiation is reflected back from the surface -The Diurnal Cycle: the balance between incoming solar radiation and earth?s outgoing long wave radiation During the day incoming solar radiation exceeds outgoing long wave radiation, so earth warms Maximum temperature occurs when solar radiation equals outgoing long wave radiation Around 5 pm -Inversions: Nocturnal Inversion: temperature inversion that develops near the ground during the evening (cooling during the evening) Clouds don?t allow an inversion to occur because they emit terrestrial energy towards earth?s surface Wind?s don?t allow inversion because they mix the cooling surface air with warmer air in the atmosphere Winter allows the inversion because nights are longer, so the sun warms the ground less and increases the inversion effects If the ground has a low specific heat capacity, it will increase the chances of the inversion because it can cool quicker Examples: very cool desert evenings Moisture in the Atmosphere -Humidity: the amount of water vapor in the atmosphere Measured by the mixing ratio Grams water vapor in air/kilograms dry air -Saturation: when air contains maximum amounts of water vapor, the air is considered saturated Actual mixing ratio/saturated mixing ratio Mass water vapor in air/mass water vapor required for saturation -Relative Humidity: indicates how close the air is to saturation A change in temperature or amount of water vapor will change relative humidity Warmer air lowers the relative humidity because molecules are more energetic, thus closer to gas phase Cooler air has a higher mixing ratio because molecules are less energetic, thus farther from gas phase If the amount of water vapor increases, the relative humidity increases -Dew Point temperature: temperature in which air must be cooled to reach saturation (actual mixing ratio) The more humid air is, the higher dew point temperature will be -Atmospheric Temperature Soundings: Inversions Types of clouds expected from different soundings -Air cools as it rises Since air expands as it rises, according to the ideal gas law, since pressure decreases with height, if volume increases, temperature decreases Moist air cools slower than dry air because as moist air rises, water condenses, slightly heating the parcel, combating the cooling process Clouds and Precipitation: -Dew formation: air cools to its dew point and then dew forms on objects -Cloud Condensation nuclei: Form from hygroscopic particles: water friendly aerosols Allows for condensation Allow clouds to form without 100% humidity -Fog: Radiation fog: occurs on long clear nights, overnight the ground cools radiatively, cooling the air, increasing the relative humidity Common in mountain and river valleys and in winter, especially in Midwestern winters Advection fog: warm air blows horizontally over a cold surface, driven by wind. Common in west coast summers Upslope fog: air cools by lifting to a higher elevation, driven by wind Common on mountain sides (upslope) Steam/Evaporation Fog: Water vapor warms enough to eventually evaporate Common in bathrooms, off the East Coast during Winter, lake Mendota during fall -Clouds: Stratus: layered, sheet like clouds Cumulus: heap, puffy like clouds Cirrus: hair, wispy like clouds Nimbus: rain clouds High Clouds (6-10km) take on the Cirro- prefix Middle clouds (2-6km) take on the Alto- prefix Low clouds (0-2km) don?t take on a prefix -Precipitation Formation: Condensation: Air cools to dew point, water vapor condenses to drops Process is too slow for drops to grow large enough Collision/Coalescence: Most likely form of precipitation to occur, occurs in warm clouds at the tops with temperatures greater than -15 degrees Celsius Drops grow larger via collisions of larger drops with smaller drops Larger drops fall faster than smaller drops causing collision and growth through coalescence -Bergeron Process: ice particles grow at the expense of liquid water droplets Occurs because saturated vapor pressure of ice is less than that of water Important process in cold clouds Creates ?hole punch clouds? Cirrus clouds are above alto cumulus clouds, ice crystals fall from cirrus clouds becoming saturated As crystals travel through alto cumulus clouds, super cooled water droplets latch onto ice crystals, causing them to evaporate and form the hole punch Stability and Lapse Rates: -Lapse Rates: the rate at which a parcel of air cools per kilometer traveled vertically -Dry vs. moist Adiabatic Lapse Rates: Dry Adiabatic Lapse Rate: -10 degrees Celsius/km Parcel cools at dry adiabatic lapse rate when it is not saturated Moist Adiabatic Lapse Rate: -6 degrees Celsius/km Parcel cools at moist adiabatic lapse rate upon reaching saturation Environmental Lapse Rate: given, varies on environment Lapse rates differ because as saturated air (cooling at the moist adiabatic lapse rate) rises, the water condenses. This process is a form of latent heating that warms the parcel, giving it negative feedback -Stability: a way of characterizing layers of air based on their temperature profiles Absolutely Unstable: environmental lapse rate>dry lapse rate Severe weather, cumulonimbus clouds Absolutely Stable: environmental lapse rate
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