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Representation of the Convectively Coupled Kelvin Waves in Modern Reanalysis Products

Presentation Date
Tuesday, January 25, 2022 at 5:00pm



Despite decades of research, fundamental questions about the convectively coupled Kelvin waves (KWs) remain not fully answered. To deepen our understanding of KWs and to test simple models for KWs, in this study we examine KW precipitation, vertical structure, and energetics in four modern reanalyses (RAs): ERA5, MERRA2, CFSR, and JRA-55. The KW precipitation signal strength in the wavenumber-frequency domain, the geographical distribution of KW precipitation, and the meridional migration of KW precipitation with seasons are reasonably represented in all RAs, although they commonly underestimate the amplitude of KW precipitation. There are considerable inter-RA differences in the vertical structure of KWs, especially in the variables that are associated with the thermodynamics of KWs (temperature, moisture, and diabatic heating). The eddy available potential energy (EAPE) production within KWs is found to be associated with the second baroclinic mode whereas the first baroclinic mode damps KW EAPE in three out of four RAs (except for JRA-55). Geographically, the KW EAPE production by the second baroclinic mode occurs in areas with environmental conditions that are favorable for upscale growth of convective systems (i.e., relatively high sea surface temperature and column moisture). Our results are supportive of the simple models for KWs in which KWs are destabilized by the second baroclinic mode.

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