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Equatorial Waves, Atmospheric Convection and the Large Scale CirculationPDE and Applied Math Seminar
|Speaker: ||George Kiladis, NOAA, Earth Systems Research Laboratory|
|Location: ||1146 MSB|
|Start time: ||Mon, Jan 10 2011, 4:10PM|
Convectively coupled equatorial waves (CCEWs) are responsible
for a large portion of the rainfall variability within the ITCZ
and monsoon regions. This talk will first review the statistical
structure of these waves and compare that structure with that
predicted by Matsuno’s classical shallow water theory on an
equatorial beta plane. An Empirical Orthogonal Function (EOF)
analysis is undertaken of global tropical (20S-20N) brightness
temperature data filtered to retain fluctuations on various synoptic
(<10 day) to submonthly (<30 day) time scales. The leading modes
correspond to known CCEW disturbances. In general
many of the modes also have strong extratropical signals
associated with them, and extratropical forcing of the equatorial
wave activity is unambiguous based on their lead-lag relationships.
One common manifestation of this type of interaction involves the
initiation of convectively coupled Kelvin waves within the western
Pacific ITCZ, which are often triggered by Rossby wave activity
propagating into the Australasian region from the South Indian
Ocean storm track. The resulting waves frequently propagate
eastward across the entire globe. In other cases,
such as over Africa, the forcing appears to be related to wave
activity in the extratropical storm track which is not necessarily
propagating into low latitudes, but appears to "project" onto the
Kelvin structure, in line with past theoretical and modeling studies.
Observational evidence for such interactions will be presented,
along with a review of some recent theoretical work aimed at
explaining their dynamical causes.
Joint with Atmospheric Sciences. Note special time. Coffee and cookies will be served in MSB 1147 beginning at 4:10 pm on the day of the seminar.