An Experimental Study of the Small-Scale Variability of Rainfall At the Southern Delmarva Peninsula

An experimental study was conducted at 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 11 sites where 8 sites had triple and remaining sites had dual tipping bucket rain gauges. The gauges were 0.01 inches resolution and the time of the tip was recorded to a data logger, which is powered by a lithium battery. A continuous gauge record was obtained at every gauge site from May 2005 to July 2010. The gauges sites were distributed from Ocean City, Maryland to Kiptopeke, Virginia, which corresponds to the maximum separation distance (150 km). A minimum separation distance of 1 km was between the two sites at Wallops Island, Virginia. This study focuses on the variability of rainfall at different climatological periods as well as 4 distinct weather systems. The observations were divided into 20 seasons, 10 cold/warm periods, and 5 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 felt below 50% at 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 in fall and spring between the years. These seasons are subject to various weather events. For example, the remnants of tropical cyclones bring abundant rainfall to the Mid-Atlantic region but they may not be observed at a given year. Winter season also exhibits differences from on year to the next where the sample sizes are quite different due to snow removal from the dataset. 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.