Winds

What we know about winds

Winds move from high pressure areas to low pressure areas.

The strength of wind is determined by the pressure gradient.

The greater the gradient, the stronger the winds.

Winds turn to the right in the northern hemisphere due to the Coriolis Effect.

Wind Patterns

Wouldn’t the cold air above the north pole sink, and the hot air above the equator rise, creating a steady stream of wind?

Short answer: No

Long answer:

Nooooooooooooooooooooooooooooooooooo

The rotation of the earth makes complex wind patterns.

Wind Cells

Air does in fact rise from the equator, and sink at the poles, but it also moves vertically in other areas.

It rises at the equator (0°). Doldrums

It sinks at 30° N and S. Horse Latitudes

It rises at about 60° N and S. Subpolar Lows

It sinks at the poles (90°). Polar Highs

Wind BeltsDoldrums and Horse Latitudes:

Mainly vertical air movement.Very calm winds.Ships can become stuck for days at time.

Trade Winds:Move strongly and steadily, used for trade routes.

(North and South) Westerlies:Move strongly but not steadily.

Special Winds

Upper air winds:

Above 7500 meters, all winds become westerlies.

Below 6000m, the trade winds blow from east to west between 30°N and 30°S

The Jet Stream:

Very strong and narrow wind belt that blows from west to east in middle latitudes.

Monsoons

In winter, continents are cooler than nearby water.

This results in high pressure over the land, and low pressure over the sea.

Winds move from the land to the sea.

In summer, continents are warmer than nearby water.

This results in lower pressure over land, and higher pressure over the sea.

Winds move from the sea to the land.

Monsoons

A monsoon is the seasonal change in wind caused by the differences in pressure over land and sea.

Monsoons are common over India.

The winds turn around completely here, making it a perfect example.

The dry monsoon is during winter,

The wet monsoon is during summer.

BreezesNicknamed “the daily monsoons”

These occur routinely when air over the land and nearby sea develop different pressures over the course of the day.

A sea breeze is when the wind moves in from the water to the land. Generally stronger.

A land breeze is when the wind moves out from the land to the sea.

Plotting Winds

We use symbols on a weather map to indicate wind direction and speed.

We start with a weather station, indicated by an open circle:

Direction is indicated by a line drawn from the direction wind is coming from: Easterly wind

A feather drawn on the end of the line indicates speed.

Feathers indicating speed