Term
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Definition
• Lower portion
• Tempearture decreases with height (altitude)
• 75% of atmospheric mass
• Nearly all of the water vapor and aerosols
• Deeper in the tropics; shallower at the poles
• All important weather phenomena
• Pressure also decreases with height |
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Term
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Definition
• beyond troposphere
• properties of air are independent of turbulence
• concentration of ozone
• ozone absorption of UV radiation heats the stratosphere
• higher temperatures result |
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Term
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Definition
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Term
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Definition
• High temps but very low pressure
• O2 and N2 absorb solar shortwave energy
• So little atmosphere that it doesn’t feel hot – low heat content |
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Term
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Definition
• Air is a mixture of discrete gases
• O2 and N2 make up ~99% of atm. but are largely irrelevant to weather
• CO2 present in minute amounts
• CH4 (methane) in even more minute amounts
• O2 and N2 make up ~99% of atm. but are largely irrelevant to weather
• CO2 present in minute amounts
• CH4 (methane) in even more minute amounts
• Both CO2 and CH4 concentrations have risen in recent century |
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Term
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Definition
• CO2 is 1.21 times more abundant than in the 1960s
• CH4 is 1.5 times higher than in 1750 from 700 to 1745 ppbv
• CH4 rise has recently slowed: 200 ppbv/decade in 70s, 0-130 ppbv/decade now
• Still, CH4 is more potent as GHG, 20x the CO2 effect
• Warming from a 20% rise in CO2 is like a 1% rise in CH4 |
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Term
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Definition
• Near zero to 4% by volume
• Source of all clouds and precipitation
• Hugely important for heating of the atmosphere
• Its change of phase from solid to liquid to gas absorbs or releases heat without a change in temperature
• This latent (or hidden) heat is moved with water and is a critical energy source driving some storms |
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Term
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Definition
• Ejected and suspended particles, transported by atmospheric motions and kept aloft
• Dust, soil, smoke, soot, sea salts, pollen, microorganisms
• Even some in the upper atmosphere (meteorites decompose or break apart) |
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Term
| Insolation and Heating [Section] |
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Definition
More than 99.9% of the energy that heats Earth’s surface comes from solar radiation
Not evenly distributed… varies with latitude, time of day, season of year
Unequal heating of Earth contributes to winds, ocean currents which in turn move heat from the tropics toward the poles |
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Term
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Definition
capacity to do work
Kinetic – motion
Potential – stored kinetic |
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Term
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Definition
how warm relative to some standard
Formally: the average kinetic energy of the molecules of some object
When substance gains energy… particles move faster… temperature rises OR there is a phase change |
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Term
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Definition
transfer of energy into/out of object because of temperature difference between an object and its surroundings
- Flows from high to low until equal
- heated objects take on internal energy, typically as increased molecular motion |
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Term
| Mechanisms of Energy Transfer |
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Definition
1. Conduction: direct transfers between molecules in contact (collisions)
-objects can be good or poor conductors
metals and stone are good; wood and air are poor
-here, only active for contact of Earth’s surface and air just above
2. Convection: transfer involving the movement or circulation of a substance (fluids)
-fluids flow and carry heat with their motions
-convection cells in boiling water
-thermals used by hawks, vultures, hang-gliders
3. Radiation: emission and propagation of energy in forms of waves or particles and through some material or space
-does not require a medium to travel (e.g. sun’s energy through space)
-spread across wide range of electromagnetic spectrum, waves of different sizes (frequencies or wavelengths)
-short waves are more energetic, potentially damaging, solar radiation is short |
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Term
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Definition
1) All objects emit unless at absolute zero
2) Hotter objects emit more energy (Stefan-Boltzman Law)
3) Hotter objects emit in shorter wavelengths (Wien’s Law)
4) Good absorbers are good emitters
-can be wavelength specific
-theoretical blackbody is perfect across all wavelengths
Radiation is distributed Across Frequencies of the Electromagnetic Spectrum |
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Term
| What happens to incoming solar radiation? |
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Definition
1) Absorbed: molecules vibrate faster, temp. increases
2) Transmitted: passes through the object
3) Redirected: reflection or scattering
-reflection is bouncing back at same angle and intensity
-scattering is weaker rays in different directions |
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Term
| How does Earth lose energy to space? |
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Definition
Radiant emission
Being cooler than the Sun, this emission is of longer wavelength and less intense
Incoming Radiation = shortwave
Outgoing Radiation = longwave
Gases with high absorption heat the atmosphere
The atmosphere is transparent to incoming solar radiation, the atmosphere is a good absorber of longwave radiation |
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Term
| Atmosphere is heated from |
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Definition
the bottom-up
Largely transparent to incoming shortwave radiation
- Largely absorbing of outgoing longwave radiation
- Thus, cooler with altitude in troposphere |
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Term
| Calculating the Total Absorption of a Constituent |
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Definition
intensity (I) x absorptivity (A)
I and A are functions of wavelength (l)
Wind and ocean currents Redistribute energy from Solar Radiation |
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Term
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Definition
| Short wave radiation is absorbed by earth’s surface, surface radiates long-wave radiation which is absorbed by greenhouse gasses, Greenhouse gasses re-radiate some energy back toward earth, thus trapping heat in the lower atmosphere |
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Term
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Definition
| a line that connects points on a graph (map) that have the same temperature |
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Term
| Isothermal Contour Maps show |
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Definition
1) Temperature in space
2) Temperature gradient in space… or how temperature changes with distance and direction |
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Term
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Definition
1) Latitude (variations in sun angle, length of daylight)
2) Differential heating of land and water
a. Water is a fluid and convection redistributes heating from solar radiation
b. Water, being more transparent, distributes heat vertically
c. The specific heat is three times greater for water (see next slide)
d. Evaporation of water carries heat away from wet surfaces
3) Ocean currents: responsible for about 1/4th of latitudinal redistribution of heat, wind is responsible for other 3/4ths
4) Altitude: Temperature drops about 6.5°C per km rise in the troposphere
5) Geographic position
6) Cloud cover and Albedo : Cloud cover associated with seasonal rains prevents solar radiation from reaching the surface. |
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Term
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Definition
The amount of heat needed to raise the temperature of 1 gram of a substance by 1 degree Celsius
Water has an uncommonly high specific heat capacity
It takes more energy to warm water than to warm rock, soil, plant biomass, roads, etc. |
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Term
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Definition
-Powered by energy from the Sun
-Drives evaporation into the atmosphere…
-Moisture and associated energy is carried by winds
-Precipitation and dew return it to oceans and land
-Some of this ends up as runoff, meaning leaving continental surfaces via rivers |
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Term
| To break molecular attractions |
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Definition
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Term
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Definition
is the term for how much energy is required or released by a change in phase.
This energy associated with phase change does NOT change the temperature
latent means “hidden”, hence stored energy |
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Term
| Vapor Pressure and Saturation |
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Definition
Another measure of water vapor in air is its pressure exerted on air (this is really a partial pressure)
Parcels with more water vapor exert more pressure on air
The amount of water that can be held by air is controlled by air’s temperature
If water is freely available and in contact with air in a closed system, air will demand water until it is saturated and at equilibrium |
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Term
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Definition
| : the ratio of actual to potential absolute humidity, it is defined by: (actual vapor pressure / saturated vapor pressure) |
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Term
| Adiabatic Temperature Changes result from |
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Definition
| expansion or compression of air |
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Term
| What causes air parcels to rise upwards? |
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Definition
1) Orographic lifting – air is forced to rise over a topographic barrier
2) Frontal Wedging – warmer, less dense air forced over cooler, denser air
3) Convergence – horizontal air flow piles up and is forced upward
4) Localized Convective lifting – unequal surface heating causes local pockets of hot air that then rise |
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Term
| Stability: air’s tendency to |
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Definition
| rise, sink, or stay where it is, controlled by parcel’s temperature compared to its surroundings |
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Term
| If air parcel is cooler than surrounding air it |
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Definition
| sinks and is called stable. Stability is enhanced when: Earth’s surface is radiatively cooled after sunset, an air mass is cooled from below when passing over a cold surface, there is subsidence within an air column. |
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Term
| If air parcel is warmer than surrounding air it |
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Definition
| rises and is called unstable. Instability is enhanced when: solar heating is intense, an air mass is heated from below when passing over a warm surface, lifting mechanisms are active, cloud tops are radiative cooled |
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Term
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Definition
| Two necessary conditions: 1) saturation, 2) surface for condensation |
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Term
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Definition
| Low temperature, Small water vapor source, Thin, white, icy |
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Term
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Definition
| Prefix “Alto”, typically water droplets |
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Term
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Definition
| Commonly Sources of heavy precipitation, lightning, thunder, hail |
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Term
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Definition
| a cloud with its base at or near the ground, differs in place and method of formation |
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Term
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Definition
1) By Cooling to Saturation (radiation, advection, upslope types)
2) By Addition of Water Vapor (steam, frontal types) |
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Term
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Definition
| from radiative cooling of the ground and adjacent air, requires clear skies and high relative humidity, Cold, dense air sinks into landscape lows; thick in valleys, Dissipates by evaporation, not actually through physical “lifting” |
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Term
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Definition
| Warm, moist air blown over a cold surface, then chilled by contact to its dew point; Often thick and persistent |
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Term
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Definition
| Adiabatic cooling of moist air to its dew point from winds carrying it upslope |
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Term
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Definition
| Cool air over warm water, Evaporation from water surface saturates the air just above, Shallow fog, evaporates with mixing |
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Term
| Frontal Fog (precipitation fog) |
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Definition
| Occurs after rain from frontal wedging falling where surface air is cold and nearly saturated Evaporation of rain water saturates the air and creates clouds at the surface |
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Term
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Definition
| Condensation of water vapor onto objects that are radiatively cooled to below the air’s dew point, Sometimes the grass transpires locally creating pockets of high humidity |
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Term
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Definition
| Not frozen dew, direct deposition, gas to solid, Dew point of air is below freezing |
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Term
| Conditions Needed for Precipitation |
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Definition
1. Saturation: warm air holds more water vapor
2. Condensation
3. Accumulation to Precipitable Size: Snow crystal Growth (Bergeron process): Water in three phases in the same place ( ice crystals, supercooled droplets, water vapor). Ice has a stronger affinity for gaseous water vapor than liquid droplets do, thus ice attracts and accumulates water from surrounding droplets. Collision-Coalescence Large cloud droplets fall, collide with smaller, grow, flatten from friction, split, and they fall |
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Term
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Definition
| drive winds, which influence temperature and moisture |
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Term
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Definition
| horizontal pressure differences |
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Term
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Definition
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Term
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Definition
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Term
| More Water = Lower Density |
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Definition
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Term
| Wind is nature’s attempt to |
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Definition
balance inequalities in air pressure
1) Pressure-gradient
2) Coriolis force
3) Friction |
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Term
| Unequal heating of Earth’s surface generates |
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Definition
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Term
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Definition
| Wind often deviates from the high to low path due to Earth’s rotation: Right in the North; Left in the South. Strength varies with latitude and wind speed. |
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Term
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Definition
1) Slows wind
2) Surface feature
3) Acts opposite to airflow direction
4) Thus reduced Coriolis effect that depends on wind speed |
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Term
| Convergence / Divergence Aloft |
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Definition
Air flowing together or spreading out in the upper atmosphere
Cyclones and anticyclones would not be sustained for very long without them
Surface convergence (Low Pressures) are maintained by divergence (spreading out) aloft with corresponding upward motion
Surface divergence (High Pressures) are maintained by convergence aloft with corresponding downward motion |
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Term
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Definition
| Land is heated more intensely than water. Cooler air over the water moves onto land. |
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Term
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Definition
| Land cools more rapidly than the sea, causing a land breeze |
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Term
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Definition
| Air along mountain slopes is heated more intensely than air at the same elevation over the valley floor. |
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Term
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Definition
| Rapid radiation heat loss along the mountain slopes cools the air, which drains into the valley below |
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Term
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Definition
| Cold ice sheet/snow surface cools adjacent air relative to air over ocean. Cold, dense air sinks with gravity and flows over the water. |
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Term
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Definition
| 2 Convection cells, S and N hemisphere |
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Term
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Definition
1) Radiative cooling of upper-level air
2) Coriolis force increases deflection to being nearly east-west
3) Air piles up (converges) aloft, causing subsidence
This is where we get many of the world’s deserts, reasons for dry air:
Adiabatic heating with subsidence lowers the relative humidity
Water has ‘rained out’ over the equator |
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Term
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Definition
wind systems with pronounced seasonal reversal in direction
winter cold continents, air blows off shore summer warm continents, air blows landward |
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Term
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Definition
| Narrow ribbons of high speed winds that meander for thousands of kilometers (100 – 500 km; 200 – 400 km per hour) |
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Term
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Definition
| Strong temperature gradients at the surface, generate steep pressure gradients aloft, hence faster upper air winds |
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Term
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Definition
-General west to east flow
-Shear generates a meander
-Southward excursion of cold air creates a steep temperature gradient and strong flow aloft, and…
-Steep pressure gradients which can organize rotating cyclonic systems
-These rotating systems transfer heat!
-Eventually they weaken the temperature gradient causing the system to dissipate
-Cycles last 1 to 6 weeks |
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Term
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Definition
follow the winds: Westerlies, Trade Winds, similarly deflected by Coriolis force
Upwelling: offshore winds promote rising of cold, nutrient rich water up to the surface
Cold Currents also create stable conditions over adjacent land masses, sometimes also creating fog and cool air conditions over a desert environ |
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Term
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Definition
- Cold Peruvian current and easterlies prevail
- Westward ocean current
- Warm, wet low pressure in Australia
- Cold, dry, high pressure off Western South America |
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Term
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Definition
- Strong counter current, weak Peruvian current and tradewinds
- Associated with excursions of jets
- Brings abnormally warm, wet low pressures to Ecuador
- Cooler and dryer off Indonesia |
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Term
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Definition
| - Exaggerated version of “Normal” |
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Term
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Definition
- pressure drop over southeastern Pacific
- pressure rise over western Pacific |
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Term
| Subtropical, oceanic high-pressure centers |
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Definition
| have most pronounced subsidence on the eastern side: Creates strong temperature inversion and stable atmospheric conditions, leading to dry western sides of continents and wetter eastern sides. |
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Term
| Gradient Winds and Westerlies |
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Definition
| idealized flows around low and high pressure systems located in the upper atmosphere. Circular flows parallel to the concentric isobaric surfaces in direction determined by the Coriolis force: R in N hemisphere, L in S hemisphere. |
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Term
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Definition
tropical = warm
polar = cold
arctic = coldest |
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Term
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Definition
maritime = wet
continental = dry |
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Term
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Definition
k = colder than the underlying surface
w = warmer than the underlying surface |
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Term
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Definition
| stagnant, uniform region, Air mass comes into equilibrium with the surface conditions |
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Term
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Definition
| to a region with different surface characteristics does two things: 1) modifies the conditions of the new region, 2) air mass is modified itself |
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Term
| Köppen-Geiger Classification [Section] |
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Definition
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Term
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Definition
| humid tropical, monthly T > 18°C …. winterless |
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Term
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Definition
| dry, Potential Evaporation > Precipitation |
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Term
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Definition
| humid middle-latitude, mild winters, monthly T of coldest month < 18°C, but > -3°C |
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Term
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Definition
| humid, middle-latitude, severe winters, monthly T of coldest month < 18°C, but < -3°C |
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Term
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Definition
| polar, monthly T max is < 10°C… summerless |
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Term
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Definition
Water deficiency is the key
annual precipitation < annual potential water loss to evaporation
hot, low humidity = high demand for water mainly driven by solar radiation
We define the Bs – A or C boundary based on:
1) annual precipitation
2) annual temperature
3) their seasonality… wet, warm different from wet, cold season |
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Term
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Definition
boundary surfaces that separate air masses of different densities
- typically one is warm and has more moisture
- air masses can move together
- often of different speeds and thus they “clash”
- there is little mixing when they clash, meaning they retain their character
- displacement occurs: cold, more dense air displaces warm, less dense air
- Overrunning: warm air gliding over a cold air mass |
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Term
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Definition
1. Warm front: warm air overruns cold air
2. Cold Front: cold air pushes up warm air
3. Stationary Front: cold and warm masses flow adjacent and opposite
4. Occluded Front: cold front catches up to warm front
5. Dryline: moist air lifted over denser dry air |
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Term
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Definition
red line, semicircles protruding into colder air
mT air (Gulf) meets receding cooler air
warm air wedged (overruns) over cold
surface friction slows the advance of the cold relative to the warm air
gradual sloping surface of about 1:200
cirrus clouds foretell approaching front
as front approaches, clouds get closer to surface, and more dense
low to moderate precipitation unless warm air is conditionally stable |
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Term
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Definition
cold cP air advances into a region occupied by warmer air
steeper slope of surface, with 1:100, again linked to surface friction
are more violent, with air lifted faster, thus towering clouds develop, dark band
cumulonimbus clouds, heavy downpours, vigorous winds
cold fronts generally move faster than warm fronts; important for mid-latitude cyclones |
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Term
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Definition
warm and cold fronts meet
- warm sector mT air overruns cP or mP air
- cP air pushes up mT air at the cold front |
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Term
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Definition
- fast cold front overtakes warm front
- warm air is wedged between the two cold air masses
- complex precipitation (mostly from warm air being lifted, can also be from one of the cold air masses being lifted)
- purple line and alternating triangles and semicircles pointing in direction of motion |
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Term
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Definition
- airflow parallel to the line of the front
- front does not move, hence the name
- blue triangles point on one side of line, red semicircles on the other
- can involve stalling of a cyclone or storm and hence threat of flooding
- often linked to polar easterlies on one side, westerlies on the other |
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Term
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Definition
formation of a cyclone
- stationary front
- wave develops, warm invades cold, cold invades warm
- creates low pressure and cyclonic, counterclockwise flow
- convergence, lifting, overrunning, clouds
- occlusion: the beginning of end, storm may intensify but pressure gradient weakens as the horizontal temperature difference at the surface is eliminated |
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Term
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Definition
- generated by a density gradient from humidity (not temperature)
- wet = lower density
- just like a cold front picture but hot dry (cT air) meets hot wet (mT air)
- mT air is lifted vigorously, generates intense weather, squall line, and tornadoes |
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Term
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Definition
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Term
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Definition
| lifting by unequal heating, commonly mT air becomes unstable when heated from below often in mid-afternoon, when surface temperatures are highest. 3 stages of development: A. cumulus, B. mature, C. Dissipating |
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Term
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Definition
| unequal heating plus frontal or mountain lifting, involve strong vertical wind sheer that tilts updraft portion. strong vertical wind shear from changes in wind direction or speed with height: tilts updrafts, do not extinguish themselves and allows storm to be sustained |
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Term
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Definition
| single, very powerful cell up to 20 km, persist for many hours, have rotating updrafts and hence can produce tornadoes, requires huge quantities of latent heat (warm, moisture-rich lower troposphere) |
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