Large-scale meteorology and deep convection during TRMM KWAJEX

An overview of the large-scale behavior of the atmosphere during the Tropical Rainfall Measuring Mission (TRMM) Kwajalein experiment (KWAJEX) is presented. Sounding and ground radar data collected during KWAJEX, and several routinely available data sets including GMS, NOAA OLR, and SSM/I satellite data and ECMWF operational analyses, are used. One focus is the dynamical characterization of synopticscale systems in the western/central tropical Pacific during KWAJEX, particularly those which produced the largest rainfall at Kwajalein. Another is the local relationships observed on daily time scales among various thermodynamic variables and areal average rain rate. These relationships provide evidence regarding the degree and kind of local thermodynamic control of convection. Although convection in the Marshall Islands and surrounding regions often appears chaotic when viewed in satellite imagery, the largest rain events at Kwajalein during the experiment were clearly associated with large-scale envelopes of convection, which propagated coherently over several days and thousands of kilometers, had clear signals in the lower-level large-scale wind field, and are classifiable in terms of known wave modes. Spectral filtering identifies mixed Rossby-gravity (MRG) and Kelvin waves prominently in the OLR data. “Tropical depression-type” disturbances are also evident. In some cases multiple wave types may be associated with a single event. Three brief case studies involving different wave types are presented. Daily-mean sounding data averaged over the five sounding sites show evidence of shallow convective adjustment, in that near-surface moist static energy variations correlate closely with lower tropospheric temperature. Evidence of thermodynamic control of deep convection on daily time scales is weaker. Upper-tropospheric temperature is weakly correlated with near-surface moist static energy. There are correlations of relative humidity (RH) with deep convection. Significant area-averaged rainfall only occurs above a threshold lower tropospheric RH near 80%. Above this threshold there