Abstract:

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.

Key words: persistent heat wave, diagnosis, diabatic heating, South China