Lecture 15 Upper Atmospheric Cyclone Structure TWB p 58 ET Cyclone mainly draws warm air up poleward cold air down equatorward Core of cyclone rotates counterclockwise tilts westward with height Long and Short Waves TWB p 55 Long waves 3000 5000 km ridge to trough nearly stationary Short waves 1000 2000 km ridge to trough move with 500 mb winds not always easily distinguishable Troughs cyclonic counterclockwise NH spin of winds Ridges anticyclonic clockwise NH spin Movement of Short Waves Through Long Waves EOM Vorticity Vorticity is spin of air parcel about vertical axis Total or absolute vorticity has two parts Relative vorticity Spin of air relative to earth Ambient vorticity vertical part of earth s spin Relative Ambient Ambient vorticity is large at poles zero at equator Positive ambient vort Absolute vorticity only changed by stretching No ambient vort Stretching Compression More absolute vorticity Less absolute vorticity Negative ambient vort Long Rossby waves Are set up by the pattern of oceans land and mountains around the globe Involve little stretching or compression of air columns so air keeps the same absolute vorticity as it moves from W to E throughout the wave More ambient vort in ridge Negative rel vort in ridge positive rel vort in trough Same absolute vort in both Jet stream winds N E Named after a famous meteorologist of the 1920s and 1930s who was one of the first people to recognize the role of the jet stream in weather Storms crossing over the Rockies TWB p 54 Storm Tracks Surface lows disappear over the Rockies Low formation in lee of Rockies and Gulf of Mexico Cold highs descend from Canada behind storms EOM
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