Academic Earth/Space Science : Air Pressure and Winds

Timlin, Block 3

Air pressure

Pressure exerted by the weight of air above.

Because it is exerted in all directions

Why doesn't air pressure crush things?

Mercury barometer, aneroid barometer

What instruments are used to measure air pressure?

Mercury barometer

Created by Torricelli, student of Galileo. Used by filling a glass tube closed at one end with mercury and when mercury flows out of the tube you can see atmospheric pressure.

Aneroid barometer

Uses a metal chamber with air removed it changes shape and compresses as air pressure increases, __more portable and smaller__, non-toxic.

1013.2 millibars

What is standard sea level pressure in millibars?

Torricelli, Galileo's student

Who invented the mercury barometer?

Solar radiation

What is the ultimate energy source for winds?

Generate wind

What do pressure differences do?

Pressure differences, Coriolis effect, friction

What factors influence winds?

Widely spaces isobars indicate a weak pressure gradient and light winds, whereas closely spaces isobars are opposite

What is the relationship between closely and widely spaced isobars?

Wind

The horizontal movement of air from an area of high pressure to an area of lower pressure

Jet streams

Fast moving rivers of air above the friction layer

wind blows to the right

How does the Coriolis effect influence wind in the Northern Hemisphere?

Wind deflects to the left

How does the Coriolis effect influence wind in the Southern Hemisphere?

It is strongest at the poles and weakest at the equator

Where is the Coriolis effect the strongest and the weakest?

In both hemispheres differences in air pressure cause a net flow of air __inward__ around a cyclone

How do low pressure systems appear in both hemispheres?

In both hemispheres differences in air pressure cause a net flow of air __outward__ around an anticyclone

How do high pressure systems appear in both hemispheres?

Cyclones

Centers of __low pressure__, the __pressure decreases__ from the outer isobars toward the center.

Anticyclones

centers of __high pressure__, the __pressure increases__ from the outside towards the center

Warm air rises

What happens to warm air in a cyclone?

Warm air sinks

What happens to warm air in an anticyclone?

Rainy weather

What kind of weather are cyclones associated with?

fair weather

What kind of weather are anticyclone associated with?

Air spirals in toward the center in a counter-clockwise pattern

movement of a cyclone in the Northern Hemisphere

Air spirals in towards the center in a clockwise pattern

Movement of a cyclone in the Southern Hemisphere

Air spirals outwards in a clockwise pattern

Movement in an anticyclone (Northern Hemisphere)

Air spirals outwards in a counterclockwise pattern

Movement for an anticyclone (Southern Hemisphere)

Monsoon

Seasonal changes in wind direction, __during warm months areas like India experience a flow of warm water laden air from the ocean__ which produces a rainy _________ summer.

Trade winds

two belts of winds that blow almost constantly from easterly directions and are __located on the north and south sides of the subtropical highs.__

Westerlies

dominant __west-to-east__ motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highs.

Polar easterlies

winds that blow from the polar high toward the subpolar low. These winds are not constant like the trade winds.

Equatorial low

a belt of low pressure lying near the equator and __between the subtropical highs__

subtropical high

A belt of high pressure located at approximately 30o N and 30o S, which pushes heavy subsiding air outward toward both north and south.

Subpolar low

belt of low air pressure at about 60 degrees north and 60 degrees south latitude

Local winds

Small winds produced by a locally generated pressure gradient, __caused by topographic effects or by variations in surface composition, land and water, in the immediate area.__

Global winds

winds that blow steadily from specific directions over long distances

Sea breezes

During daylight hours, the air above land heats and rises, creating a local zone of lower air pressure. __Cooler, denser air over the water moves onto the land.__

Land breezes

At night the __land cools more rapidly than the sea__ generating an offshore flow.

Anemometer

What instrument is used to measure wind speed?

After the direction from which they come

How are winds named?

El Niño

At irregular intervals of 3–7 years, these warm countercurrents become unusually strong and __replace normally cold offshore waters with warm equatorial waters__. Episodes of ocean warming that affect the eastern tropical Pacific.

La Nina

When surface temperatures in the eastern Pacific are colder than average.

Things like fishing and farming in a negative way especially to countries in the Southern Hemisphere

What does El Niño effect?

Strong winds

what do close isobars indicate?

light winds

What do widely spaced isobars indicate?