Technique for Improving Detection of WSR-88D Mesocyclone Signatures by Increasing Angular Sampling

Abstract

The Doppler velocity signature of a thunderstorm mesocyclone becomes increasingly degraded as distance from the radar increases. Degradation is due to the broadening of the radar beam with range relative to the size of the mesocyclone. Using a model mesocyclone and a simulated WSR-88D Doppler radar, a potential approach for improving the detection of mesocyclones is investigated. The approach involves decreasing the azimuthal sampling interval from the conventional 1.0° to 0.5°. Using model mesocyclones that cover the spread of expected mesocyclone sizes and strengths, simulations show that stronger mesocyclone signatures consistently are produced when radar data are collected at 0.5° azimuthal increments. Consequently, the distance from the radar at which a mesocyclone of a given strength and size can be detected increases by an average of at least 50% when data are collected using 0.5° azimuthal increments. The simulated findings are tested using Archive Level I (time series) data collected by the WSR-88D Operational Support Facility?s KCRI radar during the Oklahoma?Kansas tornado outbreak of 3 May 1999. With the availability of time series data, an Archive Level II dataset was produced for both 1.0° and 0.5° azimuthal intervals. One-third of the mesocyclone signatures collected using 0.5° azimuthal intervals were 10% to over 50% stronger than their 1.0° azimuthal interval counterparts.