lec_ch07 - Chapter 7: Atmospheric Circulations Scales of...

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Unformatted text preview: 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 mesoscale synoptic scale planetary scale Lots of important weather events occur on microscales, like evaporation of liquid water molecules from the earth's surface. Fig. 7-2, p. 171 Eddies Big and Small eddy rotor wind shear turbulence Wind shear can sometimes be observed by watching the movement of clouds at different altitudes. Kelvin Helmholtz waves Clear-air turbulence Billow clouds Figure 1, p. 173 Local Wind Systems Thermal Circulations isobars and density differences thermal circulations 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. Fig. 7-6, p. 175 Seasonally Changing Winds the Monsoon Monsoon wind system India and eastern Asian monsoon other monsoons Fig. 7-10, p. 178 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. Katabatic Winds Strong drainage winds: steep slope Katabatic winds are quite fierce in parts of Antarctica, with hurricane-force wind speeds. Bora: a cold, gusty northeasterly wind along the Adriatic coast in the former Yugoslavia Chinook (Foehn) Winds Chinook winds--warm and dry 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. It is called a Foehn along the leeward slopes of Alps. 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. Difference between this and Chinook wind Santa Ana: from elevated desert plateau; Chinook: from cold plateau Desert Winds usually with a diameter of a few meters and a height of <100 m dust and sand storms dust devils from surface cause: unequal heating of the earth's surface effect: atmospheric heat transport General Circulation of the Atmosphere Ocean currents also transport heat from the equator to the poles and back. Singlecell Model basic assumptions: no rotation Hadley cell why is the singlecell model wrong? One of the world's premier atmospheric science research facilities,the Hadley Centre for Climate Research, is named after George Hadley. model for a rotating earth Hadley cell Many global circulation terms, doldrums including `trade winds' and subtropical highs `doldrums', were named by trade winds mariners who were well acquainted intertropical with wind patterns. convergence zone Upper troposphere easterly is westerlies inconsistent with the observed polar front westerly polar easterlies Threecell Model Fig. 7-21, p. 185 semipermanent highs and lows Bermuda high & Pacific high Icelandic low & Aleutian low Siberian high Average Surface Winds and Pressure: The Real World The Bermuda High frequently brings hot, muggy weather to the eastern US. in summer The ITCZ shifts toward the north in July (from January) Fig. 7-22a, p. 188 Fig. 7-22b, p. 189 ITCZ, midlatitude storms, polar front The General Circulation and Precipitation Patterns Most of the world's thunderstorms are found along the ITCZ. Low rainfall over the subtropical regions jet streams subtropical jet stream polar front jet stream Low-level jet stream over the Central plains of the U.S. (within 2 km above surface), bringing moist and warm air to form nighttime thunderstorms Westerly Winds and the Jet Stream Global wind-driven ocean current Fig. 7-29, p. 193 Winds and Upwelling Upwelling is strongest when wind is parallel to the coastline El Nio events Southern Oscillation La Nia teleconnections El Nio and the Southern Oscillation ENSO is an example of a global-scale weather phenomenon. Often Arizona has a wetter winter during El Nino and a drier winter during La Nina; Usually northwestern U.S. has a drier winter during El Nino and a wetter winter during La Nina. Fig. 7-32, p. 196 North Atlantic Oscillation Arctic Oscillation: pressure difference between Arctic and regions to its south Other AtmosphereOcean Interactions Pacific Decadal Oscillation Fig. 7-36, p. 199 ...
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This note was uploaded on 04/06/2008 for the course NATS - 101 taught by Professor Zeng during the Fall '07 term at University of Arizona- Tucson.

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