Variational pseudo multiple-Doppler analyses of a dryline utilizing very-high resolution mobile Doppler radar data.

Abstract

The dryline has long been associated with the development of severe thunderstorms in the southern Plains during the spring and early summer months. The propagation and structure of the dryline are closely tied to surface processes that are neither well-understood nor well-resolved with current observational capabilities. As a result, there are often large errors in forecasts of dryline position and structure.

A ground-based variational pseudo-multiple Doppler processing technique is introduced, which is used to decompose time series of RHI velocity data into horizontal and vertical wind components. Results of observation system simulation experiments (OSSEs) with both an analytic and LES data set indicate the technique very accurately retrieves the individual components of motion. Further, the OSSE results highlight shortcomings of the technique. Finally, the technique is applied to a retrograding dryline from 22 May 2002. Fine-scale structure of the retreating dryline interface is presented.

Improvements in radar technology have allowed for better observations of the dryline in recent years. Here, very-fine scale radar observations taken with the mobile UMass W-band radar during a double-dryline IHOP event on 22 May 2002 in the Oklahoma panhandle are presented. The observations are placed in the context of the dryline secondary circulation, which describes flow in a plane normal to the dryline. The narrow half-power beamwidth of the antenna on the W-band (0.18 deg) permitted the measurements of channels of upward (10 m s-1 over a horizontal distance of 50--100 m) and downward (-6 m s-1 over a horizontal distance of 1 km) vertical velocity, greater in absolute magnitude than that previously reported in dryline field studies.