Wednesday, 25 January 2012
Analyzing Tropical Cyclone Induced Precipitation and Flooding Using TRMM, the University of South Alabama Mesonet, and NEXRAD Data
Hall E (New Orleans Convention Center )
As hurricanes impact the Gulf Coast every year, this study investigates available precipitation datasets, their limitations, and their applications. Often, freshwater flooding from hurricanes is overlooked as more attention is given to storm surge, high winds, and embedded severe storms. However, a FEMA study conducted from 1970 to 1999 has shown that tropical cyclone induced freshwater flooding is responsible for approximately 59% of tropical cyclone related deaths. Unfortunately, accurate rainfall estimates of tropical systems are only known when the system makes an appearance on radar. Furthermore, the uncertain nature of these storms leaves a margin of error for a tropical system to stall, dumping large amounts of precipitation over an area for days. The study was conducted in two phases. In phase one, The Tropical Rainfall Measuring Mission (TRMM), the University of South Alabama Mesonet, and a combination of both datasets were compared against NEXRAD radar for three historical tropical landfalls. A regression analysis was also completed for each case. The feasibility of incorporating TRMM data into the mesonet was also examined. The results of this phase benefit the Center for Hurricane Intensity and Landfall Investigation (CHILI) by comparing datasets and demonstrating TRMM's use as a fine scale sensor. The second phase of this project utilized TRMM to aid in hurricane preparation. Hydrologic models are often used to render detailed insights into specific flooding events. These models yielded the overland flow from precipitation and soil properties as well as the resulting flood wave in local watersheds by combining precipitation data, GIS thematic layers, and Digital Elevation Models (DEMs). The results of this study were presented to the Geology Department at the University of South Alabama. While outputs of the model were achieved this term, hydrologic models require extensive calibration and validation of the input parameters. Future work could render an accurate model that utilizes TRMM data from tropical systems still out to sea, giving emergency management advance insight into tropical induced freshwater flooding.