An Experimental Study of the Small-Scale Variability of Rainfall
Student: Rigoberto Roche
Florida International University
Major: Biomedical Engineering, Mechanical Engineering
Degree Level: Master of Science
Internship Site: NASA Goddard Space Flight Center, Greenbelt, Maryland
Mentor: Dr. Ali Tokay
Abstract: An experimental study was conducted on the Mid-Atlantic region to investigate the rainfall variability within the instantaneous field of view of the microwave sensor-based satellite rainfall estimate. The study was conducted through 30 rain gauges that were deployed at 11 sites, where eight sites had triple and remaining sites had dual gauges. The gauges were tipping bucket at 0.01 inches resolution. The time of the tip was recorded to a data logger which is powered by lithium battery. A continuous gauge record was obtained at every gauge site from May 2005 to September 2010. The gauges sites were distributed from Ocean City, Maryland, to Kiptopeke, Virginia, at a maximum separation of 150 km and at a minimum separation of 1 km between the two sites at Wallops Island, Virginia. This study focuses on the variability of rainfall at different climatological periods. The observations were divided into 20 seasons, 10 cold/warm periods, and five years. A stretched exponential model was applied to the correlations of paired gauge rainfall at 30-minute integration period. Two tips (0.5 mm) were considered as the threshold for rain events. The correlations fell below 50 % at a 10 km distance most of the time in an observational period, while they were below 20% at 40 km distance. The variability was more noticeable between the seasons than between the warm/cold periods and between the years. This could, in part, be related to the sample size, partly to differences in rainfall characteristics. Additionally, the remnants of tropical cyclones bring abundant rainfall to the Mid-Atlantic region but they may not be observed at a given year. The nugget parameter was mainly above 0.95, while the shape parameter was mainly between 0.4 and 1.0. The correlation distances remained mostly less than 50 km at a given observational period.
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