Error Estimation in Wind Fields Derived from Dual-Doppler Radar Measurement

Abstract

Variance in horizontal and vertical winds are predicted when these components are computed from dual-Doppler velocity measurements combined with terminal velocity estimates and the continuity equation. Errors in horizontal wind magnitude and direction are shown to be functions of wind direction and speed as well as spatial location. Vertical wind could be estimated with errors less than a few meters per second up to altitudes near 14 km over a region 4d × 4d, where 2d is the radar separation. Vertical wind variance at high altitudes is related to accumulation of errors due to the integration of the continuity equation. The cause of wind variance is assumed to be uncertainty in mean Doppler velocity estimates produced by spectrum broadening mechanisms (e.g., shear, turbulence). Two interpolation methods, used to estimate Doppler velocity at common grid locations, are compared and their contribution to Doppler velocity variance reduction is calculated. Terminal velocity variance has been related to uncertainties in drop-size distributions and reflectivity estimate variance. The methods derived herein are applied to determine the errors in wind speeds calculated from dual-Doppler data.