4.1
Hemispheric Flow Regimes during El Nino and La Nina: An application of Sanders' "Spaghetti Diagrams"
John M Wallace, Department of Atmospheric Sciences, University of Washington, Seattle, WA
In his synoptic laboratory classes dating back to at least the mid- 1960' s, Fred Sanders promoted the use of "spaghetti diagrams"-- displays in which multiple realizations of a selected 500-mb height contour like 540 dkm were superimposed upon a single hemispheric map. This disarmingly simple display technique provides an impressionistic view of the frequency distribution of hemispheric flow configurations observed during a prescribed time interval. It has proven particularly useful in documenting the evolution of blocking events. In this presentation, spaghetti diagrams based on 10-day mean 500-hPa height charts are used to contrast hemispheric flow regimes observed during warm winters of the ENSO cycle. These diagrams reveal, not only the contrasts in the mean state of the atmosphere, but also the contrasting hemispheric flow regimes observed during the two sets of winters. For example, Alaska blocking occurs much more frequently during the cold winters.
Session 4, Large-Scale Weather Systems (Room 617)
Monday, 12 January 2004, 4:00 PM-5:00 PM, Room 617
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