The Features of Flow Pattern in Upper Level Troposphere and Energy Conversion During the Development of Meso-Scale Low Vortex
中尺度低涡发展时高层流场特征及能量学研究

A case of heavy rain occurred in a baroclinic meso-low in the middle reaches of the Yangtze River is analyzed. The height of the tropopause in the colder sector of the vortex descends clearly when the tropopause folding occurs in that area during the development of the low. The stratospheric air with larger potential vorticity moves downward to the troposphere through the folding zone. The dropping of the tropopause in the colder sector is stronger and earlier than the lifting in warmer sector . The rotational component of kinetic energy (K) needed for the vortex development obtains mainly from divergence wind kinetic energy (Kx). The potential energy P in a whole air column in the heavy rain area transfers to Kx. In other words, the conversion function C(P, Kx) is positive in the whole air column as well as at lower levels. However, the situation seems different at 100 hPa that the divergent wind kinetic energy transfers both to K and P in the vortex region . The results indicate that the flow pattern in the upper troposphere plays an important role in the development of meso-low at lower levels.