atmospheric pressure and winds Flashcards
pressure definition
force per unit area
what is atmospheric pressure
the pressure exerted by air that takes up space and has weight
why do we not feel atmospheric pressure on our bodies
the blood in our body exert an equal counter pressure on the air
how is atmospheric pressure measured
millibars (mb)
pressure at mean sea level
1013.2mb
what is a barometer
an instrument used for measuring air pressure
factors influencing atmospheric pressure
altitude, air temp and moisture content
how does altitude affect atmospheric pressure
it is highest at mean sea level and decreases with height as the atmosphere becomes less dense
how does air temp affect atmospheric pressure
cold air exerts more pressure as it is heavier
how does moisture content or humidity affect atmospheric pressure
air laden with moisture is lighter and thus exerts less pressure
what are the thermal belts
torrid, temperate and frigid
what factors assist in the creation of pressure belts
temperature and the rotation of the earth
how do the pressure belts move?
they match the movement of the sun between the Tropic of Cancer and Tropic of Capricorn. the sun moves northwards when the sun moves towards the tropic and cancer and southward when towards the tropic of capricorn
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what are the four main pressure belts
ITCZ or equatorial low pressure
subtropical high pressure
sub polar low pressure
polar high pressure
latitudes of equatorial low pressure
0-5 degrees north and south
latitudes of sub tropical high pressure
30 to 35 north and south
latitudes of sub polar low
60 to 65 north and south
latitudes of polar high
85 to 90 north and south
full form of ITCZ
inter tropical convergence zone
alternate name for ITCZ
doldrums
why is it called the doldrums
little to know wind
why is it low pressure at the equator
the suns rays fall vertically resulting in a high level of insolation causing air to heat and rise creating low pressure
why did sailors avoid the equator during earlier time
due to lack of wind when ships were designed to be carried by storng winds sailors would be stranded for months
why are there severe thunderstorms at the equator
air converges and is then carried up by the convection currents
how much of the time does equator receive precipitation
200 days
what belts extend along the tropics of cancer and capricorn
sub-tropical high
why is the subtropical belt high pressure
air rises above the equator and when it reaches troposphere it starts flowing down and converging while losing heat due to radiation. the upper air convergence and cooling causes air to subside over the subtropics resulting in high pressure
what two wind systems converge at the sub polar low pressure belts
westerlies and polar easterlies
what happens at the sub polar belt
the westerlies being warmer are forced to rice over the polar air creating an area of low pressure
what does the uplift of air at the sub polar belt cause
zone of storms
what affects air movement
air moves from high pressure to low pressure, seasonal and diurnal variations also affects air movement
why is the polar belt high pressure
low solar energy results in low terrestrial radiation resulting in cold dense heavy air that create a high pressure belt
what is wind
moving air
what is a wind vane
instrument used to study direction of wind
how are winds named
according to direction of origination eg. winds from north are north winds
what is a breeze
gentle wind
what can strong wind do
shatter window panes, cause trees to fall and collapse thatched roofs
what is an anemometer
instrument that measures wind speed
how are winds affected by rotation of earth
they are deflected by force of rotation
what is coriolis force
force that deflects wind due to rotation of earth
what is feerel’s law
states that any freely moving bodies on surface of earth are deflected to right on northern hemisphere and to left in southern hemisphere
types of winds
permanent or planetary or prevailing
periodic
local
types of prevailing or permanent winds
trade westerlies and polar
where do trade winds blow
from sub tropical high pressure belt to equatorial low pressure belt in tropical zone
which direction do trade winds blow in both hemispheres
northern they blow from north east to south west and are called north east trade winds
southern they blow from south east to north west and are called south east trade winds
where do the westerlies blow
sub tropical high to sub polar low
which direction do westerlies blow in the hemispheres
south west to north east in northern
north west to south east in southern
what happens in between 40 and 70 degrees south
westerlies have no major landforms to slow them down resulting huge force and speed and speed
where do polar winds blow
from polar high pressure to sub polar low pressure
what direction polar winds
north easterlies in north
south easterlies in south
what are periodic winds
winds that blow without fail at a certain time of the year or day
what differentiate periodic winds from permanent winds
they can change direction suddenly or deflect from original path due to seasonal varitaion in temperature or pressure
why are periodic winds caused
unequal heating and cooling in earth’s atmosphere and surface variations in atmospheric pressure
examples of periodic winds
monsoon winds and land and sea breezes
what are the monsoon winds
rain bearing winds that blow in the tropics that are of vital importance to the places they blow over and are well developed over the indian subcontinent
what pulls the south east trade winds towards the asian landmass
during summer interior of Asian landmass gets intensely heated causing pocket of low pressure while Indian Ocean remaining cool has high pressure causing wind
why is it called the south west monsoons
as the coriolis force acts on the south east trade winds they get deflected to the right and now approach the subcontinent from the south west
what is a land breeze
at night land cools down faster and there is high pressure over the land while the sea is still warm and has lower pressure causing wind to blow from land to sea
sea breeze
during day land gets heated up faster than water and has lower pressure than the sea and wind blows from sea to land
what are local winds
local winds are winds unique to well defined areas that they blow over for a particular period that only affect local weather conditions
what is the loo
the loo is a hot dry dusty wind that blows over northern plains of india during summer originating in rajasthan and carries sand to the alluvial plains of ganga
how does the loo affect local people
causes hardship
what is the alternate name for the harmattan
the doctor
what is the harmattan
a dry dusty wind that blows over north western africa from sahara to gulf of guinea between november amd march
how far can the harmattan go
till north america
what does the harmattan do
can cause severe visibility problems but also brings relief from humid heat of west african coast
what is a foehn
a warm strong and dry local wind that blows down mountains
where did the term foehn originate
european alps
by how much can foehns raise temp
30 degrees in a few hours
what are foehns known for
drying effect and making snow cover diappear rapidly
what is a chinook and where does it blow
foehn type wind that blows in the eastern flanks of rockies mountain chain in north america.
what is a chinook like
hot, dry and results in melting of snow
