The Vertical Profile of Wind and Temperature in Cyclones and Anticyclones over the Eastern Two-Thirds of the United States: A Climatology

Abstract

A climatological analysis, based upon operational surface and upper-air data from 1957 to 1994, of the wind and temperature profiles composited with respect to each quadrant of surface cyclones and anticyclones, is presented for the eastern two-thirds of the United States. The cyclones and anticyclones are located via an objective procedure. Hodographs and soundings are also composited with respect to season, geographic region, time of day, and, for cyclones only, intensity. Vertical profiles of the static-stability parameter are composited with respect to season and quadrant for both cyclones and anticyclones. The structures of mean cyclones and anticyclones are shown and discussed. A diurnal variation in hodographs (vertical shear) is found, which shows up in both cyclones and anticyclones as a rotation in the counterclockwise direction between 0000 and 1200 UTC above the boundary layer. The effect is greater in cyclones than in anticyclones. This variation is hypothesized to be in part due to a tidal oscillation and in part due to radiative?thermal effects. In the mean, a well-pronounced equatorward-directed low-level jet is resolved in the northwest quadrant of surface cyclones. Low-level jets do not show up in the mean in other quadrants of cyclones or in anticyclones. The curvature of hodographs near the tropopause is clockwise in cyclones and counterclockwise in anticyclones.