Tropical orographic rainfall regimes

This study seeks to (1) examine the variables that influence precipitation mode and structure near complex terrain and (2) analyze the vertical and horizontal structure of precipitation systems in regions of complex terrain under current climate conditions, and how it may evolve in the future. For this study, we will examine 11 years (1998-2008) of data over the tropical Andes, Hawaii, Himalayas, Sierra Madre Occidental, and Western Ghats to determine which combination of atmospheric variables plays a crucial role in precipitation development and mode. We will compare NASA MERRA Data and NCEP-II Reanalysis Data to evaluate the robustness of the NASA MERRA dataset in determining dynamic and thermodynamic variables key for understanding orographic precipitation modes. We will then use NASA MERRA Data to evaluate how specific humidity, wind speed, and wind direction relative to the terrain effect the formation of precipitation in the regions of interest. TRMM radar (3B42) data will be used to determine precipitation mode and amount, which will be compared to the regimes based on the variables above. The second portion of the study will examine the vertical and horizontal structure of radar echoes in precipitation systems near these mountain ranges. We will examine how vertical structure within precipitation systems varies as a function of height and time of day using statistical analysis using the “precipitation feature” approach. Implications for characteristic variations in microphysical processes and rainfall production will be discussed, along with implications for the vertical structure of latent heating.