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Geography class 7 > atmospheric pressure and winds > Flashcards

atmospheric pressure and winds Flashcards

1
Q

pressure definition

A

force per unit area

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2
Q

what is atmospheric pressure

A

the pressure exerted by air that takes up space and has weight

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3
Q

why do we not feel atmospheric pressure on our bodies

A

the blood in our body exert an equal counter pressure on the air

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4
Q

how is atmospheric pressure measured

A

millibars (mb)

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5
Q

pressure at mean sea level

A

1013.2mb

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6
Q

what is a barometer

A

an instrument used for measuring air pressure

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7
Q

factors influencing atmospheric pressure

A

altitude, air temp and moisture content

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8
Q

how does altitude affect atmospheric pressure

A

it is highest at mean sea level and decreases with height as the atmosphere becomes less dense

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9
Q

how does air temp affect atmospheric pressure

A

cold air exerts more pressure as it is heavier

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10
Q

how does moisture content or humidity affect atmospheric pressure

A

air laden with moisture is lighter and thus exerts less pressure

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11
Q

what are the thermal belts

A

torrid, temperate and frigid

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12
Q

what factors assist in the creation of pressure belts

A

temperature and the rotation of the earth

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13
Q

how do the pressure belts move?

A

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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14
Q

what are the four main pressure belts

A

ITCZ or equatorial low pressure
subtropical high pressure
sub polar low pressure
polar high pressure

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15
Q

latitudes of equatorial low pressure

A

0-5 degrees north and south

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16
Q

latitudes of sub tropical high pressure

A

30 to 35 north and south

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17
Q

latitudes of sub polar low

A

60 to 65 north and south

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18
Q

latitudes of polar high

A

85 to 90 north and south

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19
Q

full form of ITCZ

A

inter tropical convergence zone

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20
Q

alternate name for ITCZ

A

doldrums

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21
Q

why is it called the doldrums

A

little to know wind

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22
Q

why is it low pressure at the equator

A

the suns rays fall vertically resulting in a high level of insolation causing air to heat and rise creating low pressure

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23
Q

why did sailors avoid the equator during earlier time

A

due to lack of wind when ships were designed to be carried by storng winds sailors would be stranded for months

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24
Q

why are there severe thunderstorms at the equator

A

air converges and is then carried up by the convection currents

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25
Q

how much of the time does equator receive precipitation

A

200 days

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26
Q

what belts extend along the tropics of cancer and capricorn

A

sub-tropical high

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27
Q

why is the subtropical belt high pressure

A

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

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28
Q

what two wind systems converge at the sub polar low pressure belts

A

westerlies and polar easterlies

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29
Q

what happens at the sub polar belt

A

the westerlies being warmer are forced to rice over the polar air creating an area of low pressure

30
Q

what does the uplift of air at the sub polar belt cause

A

zone of storms

31
Q

what affects air movement

A

air moves from high pressure to low pressure, seasonal and diurnal variations also affects air movement

32
Q

why is the polar belt high pressure

A

low solar energy results in low terrestrial radiation resulting in cold dense heavy air that create a high pressure belt

33
Q

what is wind

A

moving air

34
Q

what is a wind vane

A

instrument used to study direction of wind

35
Q

how are winds named

A

according to direction of origination eg. winds from north are north winds

36
Q

what is a breeze

A

gentle wind

37
Q

what can strong wind do

A

shatter window panes, cause trees to fall and collapse thatched roofs

38
Q

what is an anemometer

A

instrument that measures wind speed

39
Q

how are winds affected by rotation of earth

A

they are deflected by force of rotation

40
Q

what is coriolis force

A

force that deflects wind due to rotation of earth

41
Q

what is feerel’s law

A

states that any freely moving bodies on surface of earth are deflected to right on northern hemisphere and to left in southern hemisphere

42
Q

types of winds

A

permanent or planetary or prevailing
periodic
local

43
Q

types of prevailing or permanent winds

A

trade westerlies and polar

44
Q

where do trade winds blow

A

from sub tropical high pressure belt to equatorial low pressure belt in tropical zone

45
Q

which direction do trade winds blow in both hemispheres

A

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

46
Q

where do the westerlies blow

A

sub tropical high to sub polar low

47
Q

which direction do westerlies blow in the hemispheres

A

south west to north east in northern

north west to south east in southern

48
Q

what happens in between 40 and 70 degrees south

A

westerlies have no major landforms to slow them down resulting huge force and speed and speed

49
Q

where do polar winds blow

A

from polar high pressure to sub polar low pressure

50
Q

what direction polar winds

A

north easterlies in north

south easterlies in south

51
Q

what are periodic winds

A

winds that blow without fail at a certain time of the year or day

52
Q

what differentiate periodic winds from permanent winds

A

they can change direction suddenly or deflect from original path due to seasonal varitaion in temperature or pressure

53
Q

why are periodic winds caused

A

unequal heating and cooling in earth’s atmosphere and surface variations in atmospheric pressure

54
Q

examples of periodic winds

A

monsoon winds and land and sea breezes

55
Q

what are the monsoon winds

A

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

56
Q

what pulls the south east trade winds towards the asian landmass

A

during summer interior of Asian landmass gets intensely heated causing pocket of low pressure while Indian Ocean remaining cool has high pressure causing wind

57
Q

why is it called the south west monsoons

A

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

58
Q

what is a land breeze

A

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

59
Q

sea breeze

A

during day land gets heated up faster than water and has lower pressure than the sea and wind blows from sea to land

60
Q

what are local winds

A

local winds are winds unique to well defined areas that they blow over for a particular period that only affect local weather conditions

61
Q

what is the loo

A

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

62
Q

how does the loo affect local people

A

causes hardship

63
Q

what is the alternate name for the harmattan

A

the doctor

64
Q

what is the harmattan

A

a dry dusty wind that blows over north western africa from sahara to gulf of guinea between november amd march

65
Q

how far can the harmattan go

A

till north america

66
Q

what does the harmattan do

A

can cause severe visibility problems but also brings relief from humid heat of west african coast

67
Q

what is a foehn

A

a warm strong and dry local wind that blows down mountains

68
Q

where did the term foehn originate

A

european alps

69
Q

by how much can foehns raise temp

A

30 degrees in a few hours

70
Q

what are foehns known for

A

drying effect and making snow cover diappear rapidly

71
Q

what is a chinook and where does it blow

A

foehn type wind that blows in the eastern flanks of rockies mountain chain in north america.

72
Q

what is a chinook like

A

hot, dry and results in melting of snow

Geography class 7 (6 decks)

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