2002年南海夏季风爆发期间南海北部海气通量分析与比较

Analysis and Comparison of Air-Sea Flux in the Northern South China Sea (SCS) During the Monsoon Onset in 2002

基于2002年南海夏季风期间西沙海气通量观测试验,采用梯度廓线法计算了观测期间的动量通量、潜热通量、感热通量及其相关要素,并进行了分析与对比。结果表明:南海夏季风爆发前后,南海北部海气通量及其相关要素等都存在显著差异,不同天气形势下也有较大变化;南海北部海域在全球海气相互作用中的影响可能不如西太平洋显著;平均而言,三次试验的南海北部海气通量变化较小,感热通量与潜热通量之间存在比较稳定的比例关系,鲍恩比(Bowen Ratio)维持在大约0·05。

From 24 April to 22 June 2002, before and after the South China Sea （SCS） monsoon onset, the 3rd experiment of air-sea flux observation was carried out at Xisha Qundao（16°50′N, 112°20′E） which is located in the northem part of South China Sea. A series of high quality and high frequency （1 time/min） data were gained in the experiment. Based on the datasets and the NCEP data at the same time, firstly this paper suggests that the summer monsoon onset firstly in the northern part of the SCS on 14 May and it onset in the whole SCS on 16 May by diagnosing the 850 hPa wind field. Secondly the momentum flux, sensible heat flux, latent heat flux and some other correlated factors are calculated and analyzed by flux-profile method. Thirdly the air-sea fluxes between the western Pacific and the South China Sea are compared in the past years to find their common and different characteristics. The three main results are shown as follows： （1） In the experiment, the mean momentum flux was 0. 0458 W · m^-2, the mean latent heat flux was 94.06 W · m^-2 , and the mean sensible heat flux was 4.07 W · m^-2. The three fluxes were smaller than those in the western Pacific. （2） The air-sea fluxes in the northern part of the SCS and their correlated factors were remarkably different before and after the SCS monsoon onset, and they also varied greatly under different weather conditions. Every factor evolved stably besides the daily variation before the monsoon onset. But after the monsoon onset, the daily variation enhanced, the high frequency turbulence increased, and every flux varied greatly in a short time, especially in the raining phase, which reflected that the meso-scale and microscale strong turbulence occurred in the acute weather background after the monsoon onset. （3） The northern part of the SCS had the oceanic common characteristics as well as the western Pacific. Its sensible heat flux is far smaller than its latent heat flux. But the northern part of the SCS might play a less important role in the global air-sea interaction than the western Pacific. The air-sea fluxes in the northern part of the SCS changed little from May to June according to the average of the three experiments. Moreover, there was a stable ratio of the sensible heat flux to the latent heat flux. The latent heat flux was about twenty times as much as the sensible heat flux, in other words, the Bowen ratio was about 0.05.