The variation of the heat sources in East China in the early summer of 1984 and their effects on the large-scale circulation in East Asia

The distributions and daily variations of the apparent heat source (Q ₁ )and the apparent moisture sink (Q₂) in East China in the early summer of 1984 have been estimated with the budget calculation method. It has been found that during this time period, there occurred three significant episodes of strong heating that corresponded to the three events of heavy rainfalls prior to, during and post to the onset of meiyu (plum rains). The peaks of Q₁ were generally found at 200 hPa, with the heating rate of 6‡-10‡C/day observed, while the peaks of Q₂ were located at about 700 hPa, with their magnitudes being 12‡-20‡C/day. The vertical distribution of Q₁ and Q₂ indicates the importance of eddy vertical flux. In other words, the convective activity plays a very important role in the processes of precipitation in East Asia in the early summer. This result is different from the finding obtained by Luo and Yanai (1984) in their calculation of the case of 1979. They pointed out that in the early summer of 1979 the continuous precipitation dominated the region of East China. Among the three terms of Q₁ and Q₂, the maximum contribution was made from the adiabatic term, which was caused by strong ascending motion. The adiabatic cooling produced by this term may compensate for the heating created by the condensation process. In addition, it has been revealed that the three significant heating processes were closely related to the seasonal transition from spring to summer in East China. One major synoptic event associated with it showed up in the sudden jump of the upper tropospheric, subtropical jet-stream from 30‡N to 40‡N. So did the planetary frontal zone in East China.