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Geo Unit 2

Terms in this set (72)

zonal winds
winds blowing east to west or west to east
Hadley Cell
a system of vertical and horizontal air circulation predominating in tropical and subtropical regions and creating major weather patterns.
3 cell circulation model
Hadley cell, Ferrel cell, Polar cell
equatorial low
a low air pressure zone near the surface of the equatorial zone
ITCZ (intertropical convergence zone)
A region of low pressure near the equator where air masses meet. Also known as the doldrums.
Polar Cell
Weak circulation cell that occurs between 60 and 90 degrees latitude. It results from upper air masses moving northward and descending at the poles, while at the same time surface air flows south.
Ferrel Cell
Cell that moves air form 30 degrees to 60 degrees latitude
Westerlies
prevailing winds that blow from west to east between 30 degrees and 60 degrees latitude in both hemispheres
jet stream
a high-speed high-altitude airstream blowing from west to east near the top of the troposphere
Rossby waves
upper troposphere waves that play a large part in the formation of cyclones and anticyclones
sea breeze
The flow of cooler air from over an ocean or lake toward land during day
land breeze
the flow of air from land to a body of water at night
valley breeze
Warm air from the valley that blows UP the side of the mountain during the day.
mountain breeze
Heavy, cold air that flows DOWN the side of a mountain at night.
Santa Ana Winds
Winds flowing over Rockies and to West Coast/Calif. Bring dry hot weather and fuel wildfires
Foehn
a warm dry wind that blows down mountain slopes (leeward side)
Chinook
Foehn wind that descends the eastern slopes of the Rockies in N. America. "Snow eater"
Monsoon
Seasonal reversal of winds. Does NOT mean rainy season.
El Niño
Warmer than normal sea surface temps in eastern equatorial pacific
La Niña
Colder than normal sea surface temps in eastern equatorial pacific
air pressure
Force exerted against a surface by continuous collision of gas molecules
Isobar
lines of equal pressure
pressure gradient
The change in pressure from one area to another over a specific distance
3 forces affecting wind
Pressure gradient
Coriolis force
Friction
Pressure gradients
Provides movement of air; the strength of this determines wind speed
Vertical Pressure Gradient
There is a pressure gradient force directed upward

Pressure gradient force is much larger in the vertical than in the horizontal
hydrostatic equilibrium
Gravity balances strong vertical pressure gradients to create this; causes atmosphere to be held to earth's surface
Isohypse
line of constant elevation
Coriolis Force
causes the apparent deflection of winds from a straight path
Friction force
slows wind speeds and reduces Coriolis force close to the surface (looks like tumble weeds close to boundary layer)
geostrophic flow
driven by gravity and modified by the Coriolis force; Coriolis and Pressure gradient = this.
Cyclone
Low pressure; counterclockwise in North, clockworks in South
anticyclone
High pressure; counterclockwise on South, clockwise in North
Gradient flow
Straight or curved airflow pattern around a pressure center resulting from a balance of pressure gradient force and Coriolis force
Ridge
Elongated high
Trough
Elongated low
surface winds
-large winds due in part to pressures caused by global circulation of air
-winds blow from high to low pressure
dew
Condensation of water droplets onto objects; can start as liquid and solidifies into ice
drag
An opposing resistance, and gravity are two forces acting on a falling object
terminal velocity
Final speed obtained by an object falling through atmosphere. Small objects fall slower than large objects
collision-coalescence process
Large collector drop falls through a warm cloud and overtakes some of the smaller droplets
Bergeron Process
a process that produces percipitation; the process involves tiny ice crystals in a supercooled cloud growing larger at the expense of the surrounding liquid droplets
aggregation
Occurs when the joining of multiple ice crystals through the binding of surface water builds ice crystals to the point of overcoming updrafts
Virga
Visible rain shafts, but rain evaporates before reaching the ground
sleet
Forms when raindrops freeze in the air while falling - ice pellets
freezing rain
Rain that falls as a liquid but freezes into glaze upon contact with the ground.
hail
consists of layered ice, very strong updrafts required to allow precipitation this large to stay airborne
frost
Deposition (vapor to ice) of water vapor onto objects.
adiabatic process
A process in which no heat is transferred to or from the system by its surroundings.
Air parcel rising
Expansion and cooling
Air parcel sinking
Compression and warming
dry adiabatic rate
The rate at which unsaturated air cools as it rises, 10 degrees per 1000 feet
lifting condensation level
altitude at which air parcel becomes saturated
wet adiabatic rate
The rate at which saturated air is heated or cooled. 5 degree Celsius per 1000 feet
Atmospheric Stability
Refers to the tendency of an air parcel to move vertically
3 types of stability
Absolute stability, absolute instability, conditional stability
absolute stability
when the environmental lapse rate is less than the wet adiabatic rate. Air parcel remains cooler than environment and will resist rising
Entrainment
Ambient air is drawn into an air parcel
What causes air to stop rising?
A layer of stable air
Inversion
Layer of extremely stable air that causes temp to increase with altitude
Clouds
Visible aggregates of droplets of water or crystals of ice
Cirrus
wispy, feathery clouds
Stratus
clouds that form in sheets or layers
Cumulus
clouds having vertical development
low clouds
stratus, stratocumulus, nimbostratus
Middle Clouds
altostratus, altocumulus
high clouds
cirrus, cirrostratus, cirrocumulus
lenticular clouds
lens-shaped clouds that form in mountainous regions
mammatus clouds
Boob clouds
Radiation fog
Forms on clear and calm nights when temp cools to dew point
advection fog
warm, moist air moves over a cool surface
Contrails
Clouds formed as jets fly through the air. Look like long streaks.
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