atmospheric pressure Flashcards
what is atmospheric pressure
the force per unit area exerted against a surface by the weight of the air above the surface and produces changes in the weather
what are the factors affecting
Temperature
Altitude
Rotation of the earth
Water vapour
how does temperature affect atmospheric pressure
temperature of a place is inversely proportional with its atmospheric pressure,this is the reason why the equator has low pressure and the poles high pressure
how does altitude affect atmospheric pressure
as we go higher above the mean sea level,the atmospheric pressure decreases
for every 166 cm of ascent the pressure decreases by 1 degree celsius
how does the rotation of the earth affect atmospheric pressure
the poles,the speed of rotation is decreased which causes cold air to settle and creates high pressure
how does water vapour affect atmospheric pressure
air with moisture in it is lighter tha air without it
regions which are more humid experience low pressure as opposed to dry regions
what is global horizontal distribution of pressure what is its zonal feature
distribution of atmospheric pressure across latitudes and its zonal character is pressure belts
why is there a pattern of alternate high and low pressure belts
this is due to the spherical shape of the earth,different parts get haeted differently,because of that the equatorial region gets more heat than the poles and in turn has a lower atmospheric pressure(hot air rises,cold air settles)
why do pressure belts shift
due to the inclination of the earth towards the sun the differences in heating of continents,oceans and presure conditions vary greatly in january and july
what are winds and how do they occur
contrast in temperature causes changes in air density which causes variations in pressure and these variations cause horizontal movements in air,which is known as winds
what does the direction of winds depend upon
it depends on the pressure gradient and coriolis effect
pressure gradient definition
the difference in the atmospheric pressure of two different places on earth
the greater the difference,the steeper the gradient and the higher the wind speed
what is the coriolis effect
due to the rotation of earth on its inclined axis,it creates a force called the coriolis force which deflects air
to the left in the southern hemisphere
to the right in the northern hemisphere
permanent winds
blow throut the year fro latitude to latitude in respose to the latitudinal differences in air pressure
trade winds
blow from sub tropical highs to equatorial low
it means blowing steadily on a constant course
they bring heavy rainfall to the eastern coast of the continents in the tropics
they do not bring any rainfall to thw western coast of continents as they blow parallel to the shores
characteristics of trade winds
they are warm winds that pick up moisture and bring rainfall to the eastern margin of the continent and forms deserts on western margin
they move a few degrees north and south along with the overhead sea
they called north-east trade wind in the north and south-east trade winds in the south
what are the westerlies
blow from 30 to 60 degrees north and south latitude
they are onshore winds on the western side and bring rainfall while they are offshore winds in the eastern coast
characteristics of westerlies
blow from sub tropical highs to sub polar lows
stronger in the southern hemisphere due to lack of landmass
iterspersed by cyclones which causes a little drizzle
polar easterlies
originate in the north and south pole regions towards the circum polar low pressure zone
they get deflected to he west in both hemispheres
characteristics of polar easterlies
they blow from NE to SW in the northern hemisphere and SE to NW in the southern hemisphere
they very cold winds
when they blow over oceans,they become warm
what are periodic winds
they blow at regulars intervals of time and are the result of the localised difference between pressure and temperature
why does land breeze and sea breeze occur
due to differential heating of land and sea
land breeze
in the night,the sea gets heated faster and creates low pressure so the wind blows from land to sea
sea breeze
during the day,the land gets heated faster so it creates low pressure there so the wind blows from sea to land
what are seasonal winds
monsoons are periodic seasonal winds that blow in the region of SE asia and eastern australia
they develop because of the difference in heating of the continents and the oceans
local winds
restricted to only one place and may be hot or cold depending on the place the blow from
example;harmattan is a hot wind fro sahara
what is loo
in the northern part of india and pakistan a strong,hot local wind blows from the west in the summer
in the afternoon the temp is 45-50
feohn winds
a strong,warm wind develops on the leeward side of the alps.it is a very hot [temp:15 to 20] and causes melting of snow and hastens ripening of grapes
chinook winds
a similar kind of wind in the USA,Canada moves down the west slope of the rockies and keeps the grassland clean
mistral
blow from alps over france towards the mediterranian sea and brings the teperature beloe freezing point
