FLUXES AND STRUCTURES RELATED TO A JET STREAM

Abstract

Aircraft data collected during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) which took place over Wisconsin were used to explain updraft events and heat fluxes in case of a jet stream cirrus cloud. Aircraft measurements for the 31 October 1986 case are used in the calculations. Flight patterns used to gather the data were: (l) step up, (2) the spiral descent, and (3) sloping ascent. The cirrus on the 31 October case formed because of large scale moisture advection in the sloping surfaces, and shear and buoyancy convection played further role for cloud development. The goal of this study is to estimate the size of the convective cells and fluxes in the jet stream cirrus. Results showed that both turbulence and gravity wave activity were found in the region of strong shear. A strong inversion layer at about 8.7 km divided the cloud into two regions: l) a relatively unstable layer above where turbulence and gravity wave activity were observed and 2) a stable layer below where mainly gravity waves (wavelength ~ 40 km) were observed. Size of the convective cells were about 3 km.