Chapter 10, Part 2

Local Wind Systems

Question

Why do we have thunderstorms in the afternoon on many summer days in Gainesville?

1. Thermal Circulations

The pressure decreases with altitude.

2. Thermal Circulations

Warm air expands and cold air contracts.

The pressure above the warm air is thus higher than above the colder air for a given altitude.

There is a force and wind from the warmer to colder air.

3. Thermal Circulations

As air flows, the air above the colder region becomes further compressed.

This creates a high pressure near the surface.

A surface wind blows from cold to warm regions.

Sea Breeze

During the day, the water heats less than the land.

The air above the water is cooler and the air blows from water to land.

Rising air over land creates clouds.

Afternoon Showers in Florida

Because of the sea breeze, air blows from the east on the east coast and from the west on the west coast.

The converging and rising air creates clouds and rain.

Temperature and Sea Breezes

Because of sea (lake) breezes, the temperature tends to be cooler on the coast and warmer inland during the summer.

Land Breeze

At night the air cools more than the water.

The wind blows from land to sea.

Clouds created by rising air form over the water.

Winter Monsoon

In the winter a large shallow high pressure area develops over Siberia, producing clockwise flowing air that goes to the Indian Ocean and South China Sea.

Monsoon wind system = changes direction seasonally.

Summer Monsoon

In the summer air over the continents becomes much warmer and air flows in from the water, creating rain and the wet season.

Valley Breeze

During the day sunlight warms the valley walls.

The warm air rises producing a valley breeze and frequently clouds.

The process reverses at night (mountain breeze).

Clouds on Mountain Slopes

Katabatic Winds

Strong downhill winds result when air flows from a high plateau (cold, high pressure) to a valley (warmer, low).

Examples: bora (Yugoslavia), mistral (France), Columbia Gorge wind (US).

Chinook Wind

As wind blows from the West over the Rocky Mountains it looses its moisture and warms creating the warm dry Chinook wind on the eastern slope.

The warming is due to latent heat and compression.

Chinook Wall Cloud

Santa Ana Wind

Air descends from elevated desert plateau, funneling through mountain canyons, into LA basin and San Fernanodo Valley.

Air warms through compression, carries dust and sand, and dries out vegetation.

Desert Winds - Haboob

Cold downdrafts along leading edge of a thunderstorm lift dust and sand. (Shown: Pheonix, Arizona).

Desert Winds – Dust Devils

Warm rising air is twisted by wind blowing past an obstacle leading to a dust devil, whirlwind, or willy-willy.

Different from tornado where air descends.

Other Local Winds of Interest

Texas norther – intense winter storm goes east across the Great Plains through Texas. Temperatures may drop 10^o in a few hours.

Northeasters – storm develops off of east coast and moves north east along the coast. They usual bring heavy winds and snow.

Summary

Thermal circulations created by uneven heating/cooling over land and water create sea breezes, afternoon showers in Florida, and the monsoon in India and Asia.

Wind flowing over or down mountains create valley breezes, katabatic winds, the Chinook wind, and the Santa Ana wind.


	Why do we have thunderstorms in the afternoon on many summer days in Gainesville?


	Warm air expands and cold air contracts.
	The pressure above the warm air is thus higher than above the colder air for a given altitude.
	There is a force and wind from the warmer to colder air.


	As air flows, the air above the colder region becomes further compressed.
	This creates a high pressure near the surface.
	A surface wind blows from cold to warm regions.


	During the day, the water heats less than the land.
	The air above the water is cooler and the air blows from water to land.
	Rising air over land creates clouds.


	Because of the sea breeze, air blows from the east on the east coast and from the west on the west coast.
	The converging and rising air creates clouds and rain.


	Because of sea (lake) breezes, the temperature tends to be cooler on the coast and warmer inland during the summer.


	At night the air cools more than the water.
	The wind blows from land to sea.
	Clouds created by rising air form over the water.


	In the winter a large shallow high pressure area develops over Siberia, producing clockwise flowing air that goes to the Indian Ocean and South China Sea.
	Monsoon wind system = changes direction seasonally.


	In the summer air over the continents becomes much warmer and air flows in from the water, creating rain and the wet season.


	During the day sunlight warms the valley walls.
	The warm air rises producing a valley breeze and frequently clouds.
	The process reverses at night (mountain breeze).


	Strong downhill winds result when air flows from a high plateau (cold, high pressure) to a valley (warmer, low).
	Examples: bora (Yugoslavia), mistral (France), Columbia Gorge wind (US).


	As wind blows from the West over the Rocky Mountains it looses its moisture and warms creating the warm dry Chinook wind on the eastern slope.
	The warming is due to latent heat and compression.


	Air descends from elevated desert plateau, funneling through mountain canyons, into LA basin and San Fernanodo Valley.
	Air warms through compression, carries dust and sand, and dries out vegetation.


	Cold downdrafts along leading edge of a thunderstorm lift dust and sand. (Shown: Pheonix, Arizona).


	Warm rising air is twisted by wind blowing past an obstacle leading to a dust devil, whirlwind, or willy-willy.
	Different from tornado where air descends.


	Texas norther – intense winter storm goes east across the Great Plains through Texas. Temperatures may drop 10^o in a few hours.
	Northeasters – storm develops off of east coast and moves north east along the coast. They usual bring heavy winds and snow.


	Thermal circulations created by uneven heating/cooling over land and water create sea breezes, afternoon showers in Florida, and the monsoon in India and Asia.
	Wind flowing over or down mountains create valley breezes, katabatic winds, the Chinook wind, and the Santa Ana wind.