Thermal Stratification in Baiu Frontal Medium-Scale Disturbances with Heavy Rainfalls

[摘要] Thermal stratification in medium-scale (wave length of -1, 000km and period of -20 hour) disturbances in the Asian subtropical humid region is studied based on dense upper observation data. Attention is focussed on thermodynamic process associating with variation of instability in the lower troposphere (600-900mb).Generation of instability in the southeast quadrant of the disturbances was mainly due to the rise of equivalent potential temperature, which was primarily attributed to advection of high θe with southerly wind in the lower layer (-900mb). While the release of the generated instability is mainly due to differential heating in the narrow (-(200km)2) area of active convections in the disturbances.Cumulus mass flux, associated stability change and the height of cloud top in the unstable area of the disturbances are estimated by applying the cumulus parameterization scheme to the observed soundings.Soundings in the Asian subtropical humid region are compared with those in tropical squall lines in VIMHEX and GATE areas.

[学科分类] 大气科学