Surface wind fields in the vicinity of meso-convective storms as derived from radar observations : non-tornadic storms

Abstract

The objective of this investigation was to test the hypothesis that there is a determinable relationship between the true surface wind field and radar derived wind data. Data used were composed of National Severe Storms Laboratory single-Doppler radar data, surface automated mesonet (SAM) data, and tall-tower data from the Next Generation Weather Radar (NEXRAD) Interim Operational Test Facility (IOTF) Spring 1983 Demonstration. Analyses used data from storms that occurred in the data collection area on 22 April, 27 June, and 28 June 1983. The radial wind data provided by the single-Doppler radar were complemented by data derived from application of the NEXRAD Transverse Wind algorithm. This pattern translation algorithm derives a wind field through a statistical correlation technique using temporally separated scans of radar reflectivity. Data derived through the NEXRAD Transverse Wind algorithm were examined to assess the algorithm's general usability and to select operational parameters. The relationship of the derived data to other sources of surface wind data was examined in some detail. An important result of this investigation is the validation of the use of the Transverse Wind algorithm with data obtained at low elevation angles and short time spans between reflectivity scans. The use of maximum correlation coefficient and reflectivity thresholds are shown to improve the derived wind field. Single-Doppler radial velocity data, winds derived from the NEXRAD Transverse Wind algorithm, and SAM data are compared. The dissimiliar natures of the Doppler radial velocity data and the derived wind data are demonstrated. The derived wind field is shown to be closely related to the surface wind field as represented by the surface meso-analyses for three cases. A feature ("marching vectors"), which appears in areas of relatively weak uniform reflectivity, is identified in the derived wind data. The NEXRAD Transverse Wind algorithm is used for the first time in an area (gust front) where there is confidence that the vectors are derived from motions at their own level and not from some generator level.