Chapter 7: Atmospheric Circulations Scales of atmospheric motions Scales of atmospheric motions Eddies - big and small Eddies - big and small Local wind systems Local wind systems Global winds Global winds Global wind patterns and the oceans Global wind patterns and the oceans

Scales of Atmospheric Motions

scales of motion scales of motion Microscale Microscale Mesoscale Mesoscale synoptic scale synoptic scale planetary scale planetary scale Lots of important weather events occur on microscales, like evaporation of liquid water molecules from the earth’s surface.Lots of important weather events occur on microscales, like evaporation of liquid water molecules from the earth’s surface.

Eddies - Big and Small

eddy eddy rotor rotor wind shear wind shear turbulence turbulence Wind shear can sometimes be observed by watching the movement of clouds at different altitudes.Wind shear can sometimes be observed by watching the movement of clouds at different altitudes.

Local Wind Systems

Thermal Circulations isobars and density differences isobars and density differences thermal circulations thermal circulations

Fig. 7-4, p. 172 Stepped Art

Sea and Land Breezes sea breeze sea breeze land breeze land breeze sea breeze front sea breeze front Florida sea breezes Florida sea breezes Sea and land breezes also occur near the shores of large lakes, such as the Great Lakes.Sea and land breezes also occur near the shores of large lakes, such as the Great Lakes.

Fig. 7-5, p. 174 Stepped Art

Seasonally Changing Winds - the Monsoon Monsoon wind system Monsoon wind system Asian monsoon Asian monsoon other monsoons other monsoons

Mountain and Valley Breezes valley breeze valley breeze mountain breeze mountain breeze The nighttime mountain breeze is sometimes called gravity winds or drainage winds, because gravity causes the cold air to ‘drain’ downhill.The nighttime mountain breeze is sometimes called gravity winds or drainage winds, because gravity causes the cold air to ‘drain’ downhill.

Katabatic Winds drainage winds drainage winds bora bora Katabatic winds are quite fierce in parts of Antarctica, with hurricane-force wind speeds.Katabatic winds are quite fierce in parts of Antarctica, with hurricane-force wind speeds.

Chinook (Foehn) Winds Chinook winds Chinook winds compressional heating compressional heating chinook wall cloud chinook wall cloud In Boulder, Colorado, along the eastern flank of the Rocky Mountains, chinook winds are so common that many houses have sliding wooden shutters to protect their windows from windblown debris.In Boulder, Colorado, along the eastern flank of the Rocky Mountains, chinook winds are so common that many houses have sliding wooden shutters to protect their windows from windblown debris.

Fig. 7-14, p. 180

Santa Ana Winds Santa Ana wind Santa Ana wind compressional heating compressional heating wildfires wildfires Many Southern California residents regularly hose down their roofs to prevent fires during Santa Ana wind season.Many Southern California residents regularly hose down their roofs to prevent fires during Santa Ana wind season.

Desert Winds dust storms dust storms dust devils dust devils

Global Winds

General Circulation of the Atmosphere cause: unequal heating of the earth’s surface cause: unequal heating of the earth’s surface effect: atmospheric heat transport effect: atmospheric heat transport Ocean currents also transport heat from the equator to the poles and back. Ocean currents also transport heat from the equator to the poles and back.

Single-cell Model basic assumptions basic assumptions Hadley cell Hadley cell why the single-cell model is wrong why the single-cell model is wrong One of the world’s premier atmospheric science research facilities,the Hadley Centre for Climate Research, is named after George Hadley.One of the world’s premier atmospheric science research facilities,the Hadley Centre for Climate Research, is named after George Hadley.

Three-cell Model model for a rotating earth model for a rotating earth Hadley cell Hadley cell doldrums doldrums subtropical highs subtropical highs trade winds trade winds intertropical convergence zone intertropical convergence zone westerlies westerlies polar front polar front polar easterlies polar easterlies Many global circulation terms, including ‘trade winds’ and ‘doldrums’, were named by mariners who were well acquainted with wind patterns.Many global circulation terms, including ‘trade winds’ and ‘doldrums’, were named by mariners who were well acquainted with wind patterns.

Fig. 7-21, p. 185

Average Surface Winds and Pressure: The Real World semipermanent highs and lows semipermanent highs and lows Bermuda high & Pacific high Bermuda high & Pacific high Icelandic low & Aleutian low Icelandic low & Aleutian low Siberian high Siberian high The Bermuda High frequently brings hot, muggy weather to the eastern US.The Bermuda High frequently brings hot, muggy weather to the eastern US.

Fig. 7-22a, p. 188

Fig. 7-22b, p. 189

The General Circulation and Precipitation Patterns major controls major controls ITCZ, midlatitude storms, polar front ITCZ, midlatitude storms, polar front Most of the world’s thunderstorms are found along the ITCZ.Most of the world’s thunderstorms are found along the ITCZ.

Westerly Winds and the Jet Stream jet streams jet streams subtropical jet stream subtropical jet stream polar front jet stream polar front jet stream

Global Wind Patterns and the Oceans

Winds and Upwelling upwelling upwelling wind flow parallel to the coastline wind flow parallel to the coastline Upwelling frequently occurs along the coast of California.Upwelling frequently occurs along the coast of California.

El Niño and the Southern Oscillation El Niño events El Niño events Southern Oscillation Southern Oscillation La Niña La Niña teleconnections teleconnections ENSO is an example of a global-scale weather phenomenon.ENSO is an example of a global-scale weather phenomenon.

Fig. 7-32, p. 196

Other Atmosphere-Ocean Interactions North Atlantic Oscillation North Atlantic Oscillation Arctic Oscillation Arctic Oscillation Pacific Decadal Oscillation Pacific Decadal Oscillation Other atmosphere-ocean interactions may very well be discovered in the coming years.Other atmosphere-ocean interactions may very well be discovered in the coming years.