摘要
利用2002年 '973' 中国暴雨试验(CHeRES)期间获取的常规、非常规观测资料, 对7月22～23日长江中下游地区的一次大暴雨过程进行了分析和模拟研究.分析表明, 此次降雨过程是由东北-西南向梅雨锋上发生发展的β中尺度对流云团造成.在高低空环流的共同作用下, 高空槽后干冷气流与西南暖湿气流在长江中下游地区频繁交汇, 使得中尺度对流系统得以持续发展.模拟研究发现, 由于梅雨锋云带结构比较松散, 造成降雨的强对流系统尺度较小, 仅利用常规探空资料难以理想地模拟出降雨过程中对流云团的强度、演变.为此, 采用不同同化方案同化NOAA16卫星的ATOVS资料, 对此次降雨过程进行了对比模拟试验.结果发现, 形成模式初始场时考虑间接同化ATOVS反演得出的温、湿资料, 模式虽然同样能较好地对造成暴雨的主要天气系统、降雨的主要落区以及暴雨发生的时段进行模拟, 但雨区和雨强的模拟效果没有明显改进.相比而言, 采用增量三维变分同化系统, 直接同化ATOVS资料形成初始场, 不仅可以较好地模拟出暴雨天气形势、主要影响系统, 而且对降雨的落区、强度、暴雨发生时段均有较好的反映.模拟试验结果表明, 直接同化ATOVS资料, 模拟的梅雨锋上局地暴雨强度与实际降雨量级基本一致, 且可以有效改进对流层温、湿场分布.这不仅说明ATOVS资料的使用对于提高梅雨锋上局地暴雨过程模拟效果是可行的、必要的, 而且也为该资料用于梅雨锋暴雨的预报奠定了基础.
Abstract The routine and intensive observational data of “China Heavy Rain Experiment and Study - CHeRES” are used for analyzing and simulating the heavy rain along the Meiyu front on 22 - 23 July 2002. It is found that the environmental condition between the southern edge of the westerlies and the northern rim of the subtropical high of the western Pacific is favorable for the development of Mesoscale Convective Systems（MCSs）and the occurrence of heavy rain. MCSs develop continuously over there while the low-level jet transports warm and moisture air to the south of MCSs. The heavy rain at the interface between Hunan and Hubei provinces is caused by the MCSs, which occurres and develops continuously along the incompact Baiu front. The horizontal scale of these MCSs is much smaller and the life cycle is less than 6 hours. Because there are some difficulties in simulating the heavy rain occurring along the incompact Baiu front by only using the routine observational data, it is worth to do the simulation by using some intensive observational data, such as ATOVS. Using the MM5 model, three experiments, i. e., NOATOVS, INDIRATOVS and DIRATOVS, are performed to simulate the heavy rain process. In Experiment NOATOVS, only the conventional radiosonde and surface data are analyzed using a successive correction scheme on the basis of first guess. And in Experiment INDIRATOVS, the conventional radiosonde observations and temperature, humidity obtained from the retrieval of ATOVS, which can be called indirect assimilation, are analyzed on the basis of first guess. In Experiment DIRATOVS associated with the radiosonde observations, brightness temperatures of ATOVS at 0600 UTC 22 July and 1800 UTC 22 July are directly assimilated to form the initial field of the model. The simulated studies are focuses on understanding the influence of the ATOVS radiance data on the numerical simulation of the mesoscale convective systems in Meiyu front. By analyzing the results of the experiments, it is found that （1） although
出处
《大气科学》
CSCD
北大核心
2005年第5期780-794,共15页
Chinese Journal of Atmospheric Sciences
基金
国家重点基础研究发展规划项目2004CB418307
中国科学院知识创新工程重要方向项目KZCX3-SW-213
中国科学院奥运科技项目KACX1-02
