We propose to use TRMM precipitation radar (PR) data to study the dynamics of synoptic-scale weather variability over the tropical oceans. Large rain events over the tropical oceans are often associated with convectively-coupled wave disturbances of specific types, such as Mixed Rossby-Gravity waves, Kelvin waves, etc. Different wave types have different dynamical characteristics, so their interaction with deep convection may be different, and preliminary work with surface radar data from Kwajalein Atoll shows that this is the case. The proposed work will generalize and broaden these preliminary results using the PR data. An understanding of the differences in precipitation structure between wave types may lead to new insights into the mechanisms by which convection is modulated on large scales over tropical oceans. In simple terms, we will use the PR data to understand how weather disturbances which have different fluid dynamics on the large scale induce different dynamics in the precipitation systems on smaller scales.
Meteorological analyses and satellite observations will be used to identify and classify wave events, and then PR data will be used to characterize the convective systems associated with different wave types. The convectively coupled waves will be identified and classified using spectral analysis following Wheeler and Kiladis. PR data will then be composited by wave type, and the composites compared. Contoured frequency by altitude diagrams (CFADs) will be used to characterize the PR data in a compact way. Radiosonde data will then be composited as well, to investigate the dynamical reasons for differences seen in the CFADs.
Our project is related to objectives under category 1.1 of the NRA, "Precipitation variability and its relationship to climate diagnostics and change'', specifically topic (1), "Analysis of TRMM and other current satellite-based precipitation information for evidence of climatically significant precipitation variations and global and/or regional tropical scales, including interrelations with other variables such as temperature'', as that is a precise description of what we will do. The precipitation variations in question are the convectively coupled waves. It also fits directly under topic (2), "Space-time properties of precipitation variations and their relationship to variations in the climate system''.
