Characteristics of precipitating systems over Costa Rica using TRMM

The distribution of convective and stratiform rain in precipitating convective systems are important for understanding and ultimately predicting local precipitation variability. Long-lived stratiform precipitation associated with mesoscale convective systems can result in large accumulations and lead to local flooding. However, accurately quantifying and characterizing precipitation is difficult, especially in remote tropical regions like Costa Rica where in situ measurements are sparse. The Tropical Rainfall Measuring Mission (TRMM) satellite carries the first spaceborne precipitation radar and is helping to fill in these gaps in our understanding of tropical precipitation characteristics. The diurnal and seasonal characteristics of precipitating systems over Costa Rica are described using the TRMM 3G68 gridded combined precipitation dataset. The characteristics analyzed include rainfall amount, frequency, rain area, and convective/stratiform classification. Of specific interest is how seasonal rainfall is related to the variability in convective and stratiform precipitation. Preliminary results show that rain frequency and area average precipitation are greatest during May through November. The percent of rain classified as stratiform has little seasonal variability, however stratiform rain area coverage shows a large increase during the months with the greatest area average precipitation. Monthly mean conditional rain rates are relatively constant, suggesting that increased precipitation in May through November is driven by the increases in rain frequency and stratiform rain area rather than increases in the intensity of precipitation. These results will ultimately form the basis for a comparison of the characteristics of seasonal flood events to the long-term climatology.