ESRL/PSD Seminar Series

PSD Flash Seminars: Hot on the trail of the elusive eastward inertio-gravity wave.

George Kiladis
NOAA/ESRL PSD Climate Analysis Branch


Mixed Rossby-gravity (MRG) waves were the first waves predicted by Matsuno's equatorial shallow water theory to be observed in the atmosphere. Hundreds of papers have been written on this important mode, starting with the pioneering work of Yanai and collaborators in the 1960's. MRG waves are the dominant control of synoptic scale convective activity over the Pacific, act as seeds for typhoons, and comprise an integral portion of the convective activity within the Madden-Julian Oscillation. MRG waves comprise the westward propagating branch of the inertio-gravity wave continuum from shallow water theory, and their signals in space-time spectra of equatorial cloudiness and vorticity merge with those of the eastward inertio-gravity (EIG) mode. Although the spectral signals for both MRG and EIG waves are very strong in the time mean, there are virtually no studies in the literature on convectively coupled EIG waves. We present evidence that, despite the fact that MRG circulations are dominant in the tropics, the convective activity associated with the EIG branch should not be considered to be independent from MRG activity for much of the time. The resulting interference between the MRG and EIG waves results in strong standing anomalies in convection of opposite sign across the equator within the ITCZ and SPCZ. These antisymmetric oscillations occur on the 3-6 day time scale and are unique to the west Pacific warm pool, the only region of the globe with a true double ITCZ.

Monday, May 12
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