Analyses of a long-term, high-resolution radar rainfall data set for the Baltimore metropolitan region

Abstract

We introduce a long-term, high-resolution radar rainfall data set for the Baltimore metropolitan area covering the 10-yr period from 2000–2009. Rainfall fields are developed at 15 min time interval and 1 km horizontal resolution for a 17,000-km² region centered on the Baltimore metropolitan area. The Hydro-NEXRAD system is used as a platform for generating radar rainfall fields. We utilize the high-resolution, 10-yr data set to characterize striking spatial heterogeneities in rainfall for the Baltimore metropolitan region, both in terms of mean rainfall and rainfall extremes. The role of complex terrain (associated with urbanization, the Chesapeake Bay, and mountainous terrain) in controlling spatial heterogeneities of rainfall climatology for the Baltimore study region is discussed. We also characterize the seasonal and diurnal variation of rainfall over the study region using the 10-yr rainfall data set, with particular focus on the diurnal variation of rainfall during the warm season. High-resolution rainfall fields are especially useful for examining the distribution of rainfall from a drainage basin perspective, as illustrated through analyses of basin-averaged rainfall rate for basins of contrasting drainage area and analyses of the duration of dry periods for small urban watersheds. Analyses and methodologies used to develop the long-term Baltimore rainfall data set are broadly applicable to other regions of the United States and in settings around the world with long-term, high-quality radar data sets.