The Diagnosis of Upper Tropospheric Divergence and Ageostrophic Wind Using Profiler Wind Observations

Abstract

Wind fields derived from a network of three VHF Doppler radars are used to calculate the mean kinematic properties of the wind field over Colorado and an area-averaged geostrophic and ageostrophic wind. A numerical technique that is equivalent to the line integral method is used to compute the kinematic quantities. Details of this technique, termed the linear vector point function method (LVPF) are discussed. The behavior of the vorticity, divergence, deformation, geostrophic wind and ageostrophic wind are examined for two case studies when the synoptic scale weather patterns over Colorado are dominated by moderately intense upper-level troughs and jet streams. We find that the computed quantities of divergence, absolute vorticity, deformation, geostrophic and ageostrophic wind are modified by the passage of the weather systems in a manner consistent with our present understanding of upper-level dynamics. In addition, temporal variations in the kinematic properties, geostrophic wind and ageostrophic wind are revealed that are beyond the resolution of the existing rawinsonde network.