A severe frontal rainband. Part III: derived thermodynamic structure

Abstract

Pressure, buoyancy and virtual potential temperature perturbations are calculated from wind fields derived from Doppler radar data taken in a surface cold front. The dynamics of the front are similar to a density current. This hypothesis is also suggested by accompanying numerical simulations of cold air outflows. The updraft at the leading edge of the cold air mass is maintained in conjunction with an upward directed pressure force. The buoyancy and virtual potential temperature data reveal a front with a substantial fraction of the cooling taking place within the first 2 km of a frontal zone. Considerable along-front variations in the pressure, wind, and precipitation field occur due to the presence of a 13-km wave. These variations in the wind field are due to the influence of the waves of the rate of frontogenesis experienced by a parcel as it moves through the frontal zone. The primary factor for the changes in frontogenesis in the direction parallel to the surface front is the variation in the confluence term. -from Authors