Research On Identify Sensitive Observation Areas And Target Data Assimilation Of The Rainstorm Processes Around Beijing

The Adaptive observation is one of the key issues of THORPEX to improve the accuracy of High Impact Weather (HIW) forecast. Estimation of sensitive areas is the most important area in adaptive observation strategy. Since the adaptive observation scheme based on ETKF was set up in2008, it has been applied to identify sensitive observation area in Jianghuai heavy rain, typhoon and freezing rain disaster etc. Considers the function of humidity factor and increase the information of atmosphere in low troposphere, the paper develops optimization scheme to make the system more suitable for high impact weather in our country. Selects the rainstorm processes around Beijing as examples of HIW, then types the rainstorm processes based on synoptic system that has main effect, identifies sensitive observation areas, describes the observation sensitive area of typical flow pattern, statistics and analysis sensitive areas in different type of the rainstorm processes, comes to conclusions of observing climatologically characteristics of the sensitive area about Beijing heavy rain caused by Mongolia-Baikal low and Western trough.The article main research results are obtained as follows:1) The optimization of ETKF adaptive observation system. The optimized adaptive observation system is the best scheme; humidity factor can make the strongest observation sensitive area more concentrate. It is more obvious in heavy rain than the snow.The information of low-level atmosphere is helpful in identification of strongest observation sensitive area.2) Describe the characteristics of observation sensitive area in each typical flow pattern. Observation sensitive area of typical Mongolia-Baikal low is concentrate on the front of the trough, sensitive area move from the northwest to the verification area over time. Observation sensitive area of typical Western trough is concentrate on the junction of Low vortex and the downstream system and it has a trend to move to the northeast.3) Statistic and analysis sensitive areas in typical flow pattern.18h before the rain, observation sensitive area of Mongolia-Baikal low is located in110-113°E,41-43°N, but observation sensitive area of Western trough is concentrate in110-115°E,43-45°N at30h before the rainstorm.4) Target observations in sensitive area have positive contribution for the quality of analysis and short-term forecast, but due to the effect of assimilation system and numerical forecast model, at sometimes, the contribution is not obvious.