Winds And Air Masses *G11 Flashcards
What are planetary winds
Major winds that blow all year over large expanses of earth’s surface
Do planetary winds blow directly north/south
No, they are deflected by Coriolis force
Land and water surfaces heat and cool at different rates, therefore…
They have differences in pressure
Air mass definition *3
A large volume of air with consistent temperature,
atmospheric pressure and
humidity
What does is mean when an air mass is unstable
Air within is likely to rise, condense and rain
What does is mean when air masses are stable
Air within is subsiding and warm so rain is unlikely
Air masses cover areas that are…
Uniform
What are the types of air masses *4
*equatorial
*polar
*tropical
*arctic + antarctic
Give characteristics of equatorial air masses *3
*covers equatorial oceans
*unstable
*hot moist air
Give characteristics of tropical air masses *3
*near the tropics
*hot,dry air
*stable
Give characteristics of polar air mass *3
occurs 50and 60* of equator
*cool air
*unstable
Give characteristics for arctic/antarctic air masses *3
*occur at poles
*very cold
*stable
Maritime air masses form…
Over sea
Continental air masses form…
Over land
What are monsoons
Seasonal winds that blow in particular tropical regions
Explain how monsoons affect weather in winter *3
Inner land is colder than the seas (Siberian plateau)
*cold air sinks and causes high pressure
*these winds (from the north) blow over land (SE Asia)
*this creates dry, pleasant weather
Explain how monsoons affect weather in summer *3
Inner land is hotter than seas (Siberian plateau)
*winds (from the south) blow towards the land (SE Asia), bringing moist air
*condensation occurs and there are heavy downpours of rain
*this creates wet and warm weather
What are fohn winds
Warm dry winds that descend from the leeward side of the mountain
Leeward side definition
Side where winds descend and warm up
Windward side definition
Side where winds (usually from sea) rise and cool down
Lapse rate definition
Rate where temperature changes in the atmosphere with altitude
Or rate of cooling
What is the Dry Adiabatic Lapse Rate *2
The rate which unsaturated air decreases with temperature an increase of height
1C per 100m
What is the the Wet Adiabatic Lapse Rate *2
The rate which the temperature of saturated air decreases with an increase of height
0.5C per 100m
Explain the cycle of fohn winds *4
*moist air rises, then cools at DALR
*when condensation begins, rising air cools at WALR
*cooling > condensation > rain/snow on windward side
*cold air sinks, then warms as it descends at leeward side
What do fohn winds cause
Serious natural disasters (drought, wildfire, floods)
