Atmospheric Circulations Meteorology 10 - Weather and Climate Fall 2008 CHAPTER 7 FOCUS: air circulation patterns on Earth

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

Scales of Atmospheric Motions

scales of motion microscale synoptic 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 rotor wind shear 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 thermal circulations

Fig. 7-4, p. 172 Stepped Art

Sea and Land Breezes sea breeze land breeze sea breeze front 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 Asian monsoon other monsoons

Mountain and Valley Breezes valley 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 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 compressional heating 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 compressional heating 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 devils

Global Winds

General Circulation of the Atmosphere cause: unequal heating of the earth’s surface 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.

Sun’s energy is not distributed evenly over Earth Tropics - more incoming radiation (red) than outgoing radiation (blue) Energy must be transported poleward

Fig. 7-29, p. 193 Stepped Art

Single-cell Model basic assumptions Hadley cell 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 Hadley cell doldrums subtropical highs trade winds intertropical convergence zone westerlies polar front 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 Bermuda high & Pacific high Icelandic low & Aleutian low 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 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 subtropical jet stream polar front jet stream

Wind in the upper troposphere: Jet Streams Subtropical Jet - Coriolis turning of Hadley cell Mid-Latitude Jet – results from a steep temperature gradient

Global Wind Patterns and the Oceans

Winds and Upwelling upwelling 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 Southern Oscillation La Niña 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

Fig. 7-33, p. 197

Fig. 7-34, p. 197

Other Atmosphere-Ocean Interactions North Atlantic Oscillation Arctic 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.

Jet Streams