Archival precipitation data set for the Mississippi River Basin: Algorithm development

Abstract

The goals of the Global Energy and Water Cycle Experiment Continental‐Scale International Project (GCIP) point to the need for high‐resolution data sets on all elements of the land surface and atmospheric hydrologic cycle. A high‐resolution precipitation data set has been derived from radar reflectivity observations taken from the National Weather Service WSR‐88D radars in the continental U.S. The data set is available for a continuous five‐year period (1996–2000) at an hourly, 4 × 4 km2 resolution for the Mississippi River Basin. Development of the data set involved data management and quality control of input radar‐reflectivity, parameter estimation for radar‐reflectivity transformation, and product accumulation and quality control of the precipitation product. Quality control algorithms for the input radar‐reflectivity included procedures to deal with radar calibration differences, an especially important problem in developing a long‐term, continental‐scale data set for diverse hydroclimatological applications. Rainfall estimation was based on a Z‐R conversion algorithm that involved an optimization technique to determine the parameters for the transformation of radar‐reflectivity to rainfall. Rainfall accumulation involved integrating to hourly, 4 × 4 km2 resolution and then visually inspecting the final product. Some limitations of the algorithm are presented and suggestions are proposed for improving the development of a long‐term, large‐scale precipitation product. Initial comparisons of the radar‐based product with a rain gauge based product after a quality analysis of both products show good agreement in the Mississippi River Basin.