global atmospheric pressure Flashcards
what is the word called when the sun heats the earths surface unevenly? and where is it greatest at?
insolation and at the equator
winds blow from the areas of high pressure to the areas of low pressure transferring heat away from the …
equator
what is a low and high pressure belt?
low-warm rising air
high-cool falling air
what are the three cells in each hemisphere?
Hadley, Ferrel and Polar
what happens at the equator?
at the equator the sun warms the earth which transfers heat to the air above causing it to rise. this creates a low pressure belt. as the air rises it cools and condenses forming clouds and rain.
from the equator what type of air moves out 30 degrees north and south of the equator
cool dry air
what happens at 30 degrees north and south of the equator
the cool air falls creating a high presser belt with cloudless skies and very low rainfall
at 30 degrees what happens when the cool air reaches the grounds surface
moves as surface winds either back towards the equator or towards the poles
what are surface winds blowing towards the equator called?
Trade winds. They blow from the SE in the southern hemisphere and NE in the Northern hemisphere
what are surface winds blowing towards the poles called
westerlies-they blow from the south west in the northern hemisphere and north west in the southern hemisphere
what happens at 60 degrees of the equator?
the warmer surface winds meet the colder air from the poles. the warmer air is less dense than the cold air so it is forced to rise creating low pressure and frontal rain (rain that forms where the warm and cold air masses meet). some of the air moves back towards t he equator and the rest moves towards the poles
what happens at the poles?
at the poles the cool air sinks, creating high pressure, the high pressure air is drawn back towards the equator as surface winds
what are ocean currents
they are large scale movements of water that transfer heat energy away from warmer to cooler regions
what are surface currents
they are caused by winds and help transfer heat away from the equator, e.g. the Gulf Stream brings warm water from the Caribbean and keeps Western Europe warmer than it would otherwise be
what are deep ocean currents driven by?
water density
what happens as water freezes at the poles?
the surrounding water gets saltier increasing its density
what happens as water gets denser?
it sinks causing warmer water to flow in at the surface-creating a current. this warm water is cooled and sinks creating a current.
the cycle of cooling and sinking moves water in a big loop round the Earth. what is this known as
thermohaline circulation
what are pressure belts caused by?
global atmospheric circulation
what are the four different climate zones?
temperate, arid, Polar and tropical
what is the temperate zone?
A low pressure belt at about 60 degrees N/S caused by rising air from two cells meeting means rainfall is frequent. Located between the tropics and poles. temperate zones have moderate summers and winters.
what is the arid zone?
sinking air from the Hadley and Ferrel cells meeting causes high pressure. rainfall is very low for almost all or most of the year
what is the polar zone?
sinking air from the polar cells creates an area of high pressure at the poles. temperatures are low all year round and there’s very little rainfall.
what is the tropical zone?
rising air from the two Hadley cells meeting causes low pressure. temperatures are hot all the time and rainfall is high.
what is the Hadley cell
the equator is intensely heated by the sun
rising air=low pressure
rising air cools it forms clouds=hot humid weather with high rainfall
air starts to move towards the north and south poles
sinks at 30 degrees north/south = high pressure
sinking air warms and dries=low rainfall deserts
air flows back to the equator = trade winds
0 degrees = tropical climate
30 degrees = desert climate
what is a Ferrel cell
30-60 degrees N/S
winds pulled towards the poles pick up moisture as they travel over oceans
warm moist air meets cold air at 60 degrees
warm air from tropics=light
cold air from poles= dense
warm air rises above the cold air
causes low pressure= unstable weather conditions
uk weather caused by this
what is a polar cell
air sinks forming high pressure (polar high)
cold air flows towards lower latitudes
air mixes at 60 degrees to form polar front
