cyclone
A swirling center of low air pressure
anticyclone
An atmospheric condition of high central pressure, with currents flowing outward.
isobar
A line on a weather map that joins places that have the same air pressure
pressure gradient
Pressure difference between two points
wind
Air moving in a specific direction
Coriolis effect
Causes moving air and water to turn left in the southern hemisphere and turn right in the northern hemisphere due to Earth's hemisphere.
friction
A force that opposes motion between two surfaces that are in contact
geostrophic
A theoretical horizontal wind blowing in a straight path, parallel to the isobars or contours, at a constant speed. The geostrophic wind results when the Coriolis force exactly balances the horizontal pressure gradient force.
windward
Facing toward the direction from which the wind is blowing
prevailing wind
Global winds that blow constantly from the same direction
trough
area of relatively low pressure
equatorial low
a belt of low pressure lying near the equator and between the subtropical highs
subtropical high
A belt of high pressure which pushes heavy subsiding air outward toward both north and south.
subpolar low
The pressure zone located at about the latitude of the Arctic and Antarctic circles.
polar high
Zone of high atmospheric pressure at high latitudes
polar easerlies
60 degrees and above
westerlies
Dominant winds of the mid-latitudes. These winds move from the subtropical highs to the subpolar lows from west to east.
trade winds
Prevailing winds that blow northeast from 30 degrees north latitude to the equator and that blow southeast from 30 degrees south latitude to the equator
northeast trades
winds above equator, below 30 N
southeast trades
winds below equator, above 30S
tropical easterlies
Band of easterly winds that exist where northern and southern trade winds converge
doldrums
a belt of calms and light winds between the northern and southern trade winds of the Atlantic and Pacific
intertropical convergence zone
An area of low pressure near or on the equator where the northeast trades and the southeast trades converge
polar front
boundary at which cold polar air meets the warmer air of the middle latitudes
jet stream
a high-speed high-altitude airstream blowing from west to east near the top of the troposphere
polar front jet stream
River of high-speed air in the upper atmosphere that flows along the polar front
subtropical jet stream
a stream near the equator used to transport moisture and energy from the tropics toward the poles
Rossby Wave
Undulations that develop in the polar front jet stream when significant temperature differences exist between tropical and polar air masses.
monsoon
A strong wind that brings heavy rain to southern Asia in the summer
Chinook
A warm, dry wind flowing from mountain areas is common in some regions. As this wind generally occurs in winter or spring, it has the beneficial effects of moderating temperatures and melting snow.
foehn
dry wind that blows from the leeward sides of mountains, sometimes melting snow and causing avalanche; term used mainly in Europe
Santa Ana winds
when high pressure forms in the great basin east of southern CA and warm dry air is forced over the mountains where it cools as it rises and then races down the other side of the mountain
drainage wind (katabatic wind)
downslope flow of cold, dense air that has accumulated in a high mountain valley or over an elevated plateau or ice cap
land breeze-sea breeze cycle
daily cycle of local winds that occurs in response to pressure differences caused by the differential heating of land and water (Page 127)
gyre
the large, circular surface-current pattern found in each ocean
upwelling
The movement of cold water upward from the deep ocean that is caused by wind.
El Nino
A warm ocean current that flows along the equator from the date line and south off the coast of Ecuador at Christmas time.
Southrrn Oscillation
the systematic variation in atmospheric pressure between the eastern and western pacific ocean.
La Nina
a change in the eastern Pacific Ocean in which the surface water temperature becomes unusually cool
North Atlantic Oscillation (NOA)
climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high.
Atmospheric Pressure
force exerted by gas molecules
Dynamic High
strongly descending air is usually associated with high pressure at the surface
Thermal High
very cold surface conditions are a\often associated with high pressure at the surface
Dynamic Low
strongly rising air is usually associated with low pressure at the surface
Thermal Low
Very warm surface conditions are often associated with relatively low pressure at the surface
Barometer
An instrument that measures atmospheric pressure
Millibar
Metric unit of atmospheric pressure
Ridge
an elongated area of relatively high pressure
Pressure Gradient
Pressure difference between two points
Wind
Air in motion
Horse Latitude
are regions of high pressure and gentle winds at about 30 degrees north and south latitude
antitrade winds
Tropical upper-atmosphere westerly winds at the top of the Hadley cells that blow toward the northeast in the Northern Hemisphere and toward the southeast in the Southern Hemisphere.
Valley Breeze
The movement of air created by warm air rising and flowing up the slope of a mountain.
Mountain Breeze
The movement of air caused by cool air sinking and moving down the slope of a mountain.
walker Circulation
An atmospheric circulation of air at the equatorial Pacific Ocean, responsible for creating ocean upwelling off the coasts of Peru and Ecuador. This brings nutrient-rich cold water to the surface, increasing fishing stocks.
Southern Oscillation
a reversal of airflow between normally low atmospheric pressure over the western Pacific; the cause of El Nino
El Nino Southern Oscillation
the periodic changes in winds and ocean currents, causing cooler wetter conditions in southeastern US and usually dry weather in southern Africa and southeast asia
Teleconnections
widely spaced interactions between ocean surface temperature and weather conditions.
Explain why atmospheric pressure decreases with altitude
The density of the atmosphere decreases with altitude, and so pressure decreases
Is descending air more likely to be associated with high or low atmospheric pressure at the surface? Rising air?
Decending air is most likely associated with high atmospheric pressure at the surface, whereas rising air is more likely to be associated with low pressure.
How does friction influence the direction of wind flow?
In the lowest 1000 meters of the atmosphere, friction slows the wind, and so the amount of Coriolis effect deflection decreases
What is the pattern of wind circulation associated with a surface cyclone in the Northern Hemisphere?
Wind converges in a counterclockwise direction in a surface cyclone in the Northern Hemisphere
Describe the direction of vertical air movement within an anticyclone
Air decends towards the surface in an anticyclone
Describe the pattern of air movement within the Hadley Cells
Warm air rises near the equator ; by an alititude of about 15 kilos, the air spreads north and south and decends towards the surface at about 30 N and S, where sis moves back towards the equator to be uplifted again in the Hadley Cells.
What are the 7 components of the general circulation?
intertropical convergence zone (itcz)
trade winds
subtropical highs
westerlies
polar front (subpolar low)
polar easterlies
polar highs
Describe the general locations and the kind of weather associated with the subtropical highs
Subtropical highs are generally located over the ocean, just off of the west coasts of continents at about 25 - 30 N and S. Weather is generally sunny and dry.
Describe the general location and kind of weather associated with the ITCZ
The ITCZ is generally near the equator; weather is characterized by clouds, thunderstorms and rain.
what is the relationship of the subtropical highs to the trade winds and the westerlies
The trade winds and westerlies diverge from the subtropical high
what are jet streams and where they are usually found?
Jet streams are high speed currents of air in the upper troposphere; in each hemisphere one jet stream is generally located just poleward of the subtropical highs, and on just eastward of the polar front.
Why does the location of the ITCZ shift north during the Northern Hemisphere summer?
The position of the ITCZ shifts with the seasons, following the location of the greatest insolation and surface warming.
How does wind direction in South Asia different from summer to winter?
During the summer monsoon, winds blow onshore, off the ocean; during the winter monsoon, wind blows offshore.
How do sea breezes form?
Warming of land during the day creates relatively lower pressure over land, so the wind blows off the water toward land
how do the trade winds differ during an el Nino event compared with the normal pattern?
During an el nino event the trades weaken or reverse directions.
What is a teleconnection? Describe one example of teleconnection
It is a connection between the weather or the ocean in one part of the wold with that in another. For example, during a strong el nino, the north atlantic ocean usually experiences fewer hurricanes