利用华南观测的逐日最高气温资料和 NCEP 逐日再分析资料, 对 2003 年 6 月 29 日—8 月 15 日华南持续高温过程的大气环流背景、动力和热力条件进行了诊断分析。结果表明, 2003 年 6 月 29 日—8 月 15 日华南大范围持续高温的前 2 段高温峰期与副高有关, 第 3 段高温期大陆高压有关, 而且 3 次高温过程都与热带气旋外围下沉气流有密切联系, 而前 2 次持续高温的缓解都与热带气旋登陆和影响华南地区有密切联系。热力诊断发现, 3 段持续高温期间, 近地层大气的局地增温主要是由非绝热加热作用(白天地表感热通量和地面长波辐射加热)造成的, 水平温度平流对局地增温作用有负贡献。高温天气过程的晴空少云天气背景有利于白天太阳辐射加热地面, 并可造成明显的地面感热通量和地面长波辐射加热近地面层大气, 从而导致了持续高温天气过程。

Abstract: Based on the observational data (daily maximum surface air temperature over South China) and the NCEP/NCAR reanalysis data, three persistent extreme heat waves in the summer of 2003 are examined in terms of atmospheric circulation background and thermal dynamic conditions. It is found that these three persistent heat wave periods occurred in South China were related to the western Pacific subtropical high, the subtropical continental high, and sinking motion of upper outflow of tropical cyclone. The termination of the first two heat waves resulted from the landfall of tropical cyclones in South China. According to the diagnosis, local heating during the heat wave period was largely caused by the diabatic heating because of the daytime sensible heat flux and the upward long-wave radiation from the surface, while the horizontal temperature advection term showed a negative (cooling effect) contribution to this local heating. Compared with the diabatic heating, the vertical temperature advection term associated with descending motion contributed less to the local heating. Obviously, the descending motion provided a sunny weather in favor of the solar radiation directly down to the ground surface that led to remarkable sensible heat flux and long-wave radiation near the surface, which was favorable for these three persistent heat wave events in South China in the summer of 2003.