weather and climate 1.4 Flashcards
what is a pressure gradient? [1 point]
the difference in atmospheric pressure between 2 places
what is atmospheric pressure?
[1 point + bonus point]
the amount of force exerted on a given surface by air. (measured in millibars, using a barometer)
- atmospheric pressure decreases, altitude (height above sea level) increases. (inversely proportionate)
what is the coriolis effect? [1 point]
the deflection taken by a free-moving object as they travel over the earth’s surface due to the earth’s rotation.
how are winds formed? [4 points]
wind occurs due to the unequal distribution of air temperature, which results in an uneven distribution of pressure gradients.
in places with higher temperatures, air is heated, becomes less dense, and rises. this results in a void and lower atmospheric pressure.
in places with lower temperatures, air is cooled, becomes denser, and sinks. this results in higher atmospheric pressure.
air moves from the area of higher atmospheric pressure to the area of lower atmospheric pressure to fill the void. hence, wind is formed.
what determines wind speed?
[2 points and 4 sub-points]
- strength of pressure gradient.
smaller pressure gradient: smaller difference in pressure between two areas, leading to slower wind speeds.
larger pressure gradient: larger difference in pressure between two areas, leading to faster wind speeds.
- friction.
as moving air comes into contact with variations in the earth’s topography, it experiences frictional drag which reduces wind speed.
the effect of frictional drag is greatest where there is uneven relief and rough surfaces on land. (valleys, mountains)
why does wind vary across the earth’s surface on a local scale: land breeze?
[4 points]
in the night, both land and sea lose heat through long-wave radiation.
the SEA and air above it loses heat slowly (slower than LAND). the warmer air is less dense and rises, forming an area of lower atmospheric pressure over the sea.
on the other hand, the land and the air above it loses heat quickly. the cooler air is denser and sinks, forming an area of higher atmospheric pressure over the land.
air moves from an area of higher atmospheric pressure over the land to an area of lower atmospheric pressure over the sea, forming the land breeze.
(sea H-> land L)
why does wind vary across the earth’s surface on a local scale: sea breeze?
[4 points]
in the day, heat from the sun is absorbed by both the land and sea through short-wave radiation.
the land and the air above it gain heat quickly. the warmer air is less dense and rises, forming an area of lower atmospheric pressure over land.
the sea and the air above it gain heat slowly. the cooler air is denser and sinks, forming and area of higher atmospheric pressure over the sea.
air moves from an area of higher atmospheric pressure to an area of lower atmospheric pressure, forming the sea breeze.
(land H-> sea L)
why does wind vary across the earth’s surface on a regional scale? [2 point]
air moves across the earth over different regions from high pressure to low pressure zones.
as winds travel over large distances, they are deflected by the coriolis force. this occurs due to the earth’s rotation.
how does the coriolis effect affect wind direction in the northern and southern hemispheres? [2 points]
in the nh, winds deflect to their right,
in the sh, winds deflect to their left.
describe the formation of the northeast monsoon. [4 points]
season and temperature
pressure difference
wind direction and Coriolis effect
effect on climate
from oct to feb, the nh experiences winter and cooler temperatures. the sh experiences summer and warmer temperatures.
nh: air cools and sinks, forming an area of higher atmospheric pressure over Central Asia.
sh: air warms up and rises, forming an area of lower atmospheric pressure over Australia.
air thus moves from Central Asia (higher) to Australia (lower).
as the winds travel towards India, they are deflected to their right due to the Coriolis effect, thus forming the northeast monsoon which is experienced by countries such as Singapore, India and Malaysia.
- the ne monsoon is dry and cool as little moisture is picked up from Central Asia, thus India experiences little rain
- as the winds blow over the South China Sea, the winds pick up moisture in the form of water vapour, which brings heavy rain to areas such as Singapore.
- when the winds cross over into the sh, they deflect to the left, and continue to pick up moisture from the Indian Ocean, which brings rain to countries like Indonesia and Australia.
describe the formation of the southwest monsoon. [4 points]
season and temperature
pressure difference
wind direction and Coriolis effect
effect on climate
from June to Sept, nh experiences summer and higher temperatures. sh experiences winter and lower temepratures.
in the nh, air warms up and rises, forming an area of lower atmospheric pressure over Central Asia. in the sh, air cools and sinks, forming an area of higher atmospheric pressure over Australia.
air thus moves from Australia (higher) to Central Asia (lower). when the winds cross into the northern hemisphere, they are deflected to the right, forming the southwest monsoon which is experienced by countries such as India, Singapore, Malaysia.
as the winds move over the Indian Ocean, they pick up moisture over the Indian Ocean, bringing heavy rain to India.
