GridRad: A New High-Resolution Four-Dimensional Gridded Radar Data Set

Since 1957, radar has been an integral aspect of meteorological observations and forecasting. The current system, known as NEXRAD WSR-88D, is a modern high-resolution network of radars that provides coverage over the United States, as well as select overseas locations. Each radar has a limited range, which varies depending on what is being measured and the topography of the surrounding region. As such, several methods to merge individual volume scans have been developed in order to analyze coverage over a larger spatial region than any single radar is capable of. Many of these methods have been designed for operational use. Previously, a comprehensive, easy-to-use, climatological radar data set has not existed.

We introduce a new data set of gridded NEXRAD composites, known as GridRad. Individual volume scans from radar stations across the continental United States are merged together at specified analysis times to create the GridRad composites. In the current version (V3.1), 125 radar stations are merged at hourly synoptic intervals. Each composite contains 2301 x 1201 x 24 grid points (roughly 66 million points). The horizontal spatial resolution is 0.02 degrees of longitude (roughly 1.5 kilometers) by 0.02 degrees of latitude (roughly 2 kilometers), with a vertical resolution of 1 kilometer. Reflectivity is currently the only base data quantity that is merged.

GridRad has many research applications, several of which are already in progress. One is to create a climatology of tropopause-overshooting convection, or overshooting tops, by analyzing the echo top heights of GridRad composites and comparing with ERA-Interim reanalysis tropopause heights. Another is the analysis of a potential weekly cycle in reflectivity and precipitation over the US, which may be driven by anthropogenic aerosols acting as cloud condensation nuclei. Many more future projects that utilize GridRad are possible.