desertification
transformation of fertile land to desert, usually by overgrazing of livestock, deforestation, or natural drought
anemometer
instrument used to measure wind speed
wind vane
instrument used to measure wind direction
aerovane
combination of anemometer and a wind vane; measures wind direction and speed
prevailing wind
direction the wind blows most frequently during a specified window of time
onshore wind
coastal wind flowing from sea to land
offshore wind
coastal wind flowing from land to sea
barometer
instrument used to measure air pressure
thermal pressure
air pressure resulting from changes in temperature
dynamic pressure
air pressure caused by air movement
pressure-gradient force
force resulting from changes in barometric pressure across earth’s surface
sea-level pressure
air pressure that has been adjusted to sea level
isobar
a line drawn on a map connecting points of equal pressure. isobars are quantitative representations of the changing molecular density of the air over a geographic region
coriolis effect
the perceived deflection of moving objects in relation to Earth’s surface
boundary layer
layer of the atmosphere where wind is slowed by friction with Earth’s surface; extends about 1km above the surface
Cyclone
meteorological system in which air flows toward a low-pressure region, creating counterclockwise circulation in the Northern Hemisphere and clockwise circulation in the Southern Hemisphere
anticyclone
meteorological system in which air flows away from a high-pressure region, creating clockwise circulation in the Northern Hemisphere and counterclockwise circulation in the Southern Hemisphere
ITCZ (intertropical convergence zone)
global band of unstable, buoyant air parcels that tracks the migration of the subsolar point
subtropical high
discontinuous belt of aridity and high pressure made up of anticyclones roughly centered on 30° north and south latitude
subpolar low
belt of low pressure roughly centered on 60° north and south and made up of cyclonic systems that bring frequent precipitation
polar high
area of cold, dense air at each pole that forms a zone of thermal high pressure
trade winds
easterly surface winds found between the ITCZ and the subtropical high, between 0° and 30° north and south latitude
doldrums
a low-wind region near the equator, associated with the ITCZ
horse latitudes
the low-wind regions centered on 30° north amd south
westerlies
surface winds that come from the west and are found in both hemispheres between the subpolar low and the subtropical high
polar easterlies
cold, dry winds originating near both poles and flowing south amd east
polar jet stream
a discontinuous narrow band of fast-flowing air found at high altitudes between 30° and 60° latitude in the Northern Hemisphere
rossby wave
a large undulation in the upper-level westerlies
sea breeze
local onshore breeze created by heating and cooling differences between water and land
land breeze
local offshore breeze created by heating and cooling differences between water and land
monsoon
seasonal reversal of winds, characterized by summer onshore airflow and winter offshore airflow
valley breeze
local upslope breeze produced by heating and cooling differences in mountainous areas
mountain breeze
local downslope breeze produced by heating and cooling differences in mountainous areas
chinook wind
local downslope wind that forms on the leeward side of the Rocky Mountains
foehn wind
downslope wind that forms on the leeward side of the European Alps
santa ana winds
winds that originate in the Great Basin and are heated adiabatically as they descend to sea level on the southern California coast and northern Baja California; often associated with major wildfires
katabatic wind
(or gravity wind) Wind that forms mainly over ice sheets or glaciers when intensely cold, dense, and heavy air spills downslope by the force of gravity