Analysis Of Baroclinic Process And Diagnostic Research Of A Rainstorm Case Occurring In North-China In Autumn

A heavy rainstorm case, occurring at North-China and Circum-Bohai-Sea Region during 9th to 12th in October 2003, was simulated here. It diagnostically analyzes large-scale flow pattern, water vapor transport/budget, hypo-synoptic-scale frontogenesis/frontal baroclinic process, and the characteristic of heat/vapor budget in meso-scale strongly convective system. Additionally, regional average budget of kinetic energy was also calculated. The conclusions are as following:1) Upper level of the troposphere above the precipitating region is dominated by anti-cyclonic divergent flow. Cold-dry-mass from the north and warm-moist-mass from the south converge intensively at the lower level of this region which induces saddle-pattern-disposition, warm shear and inverse trough. Sub-tropical high and the low-pressure system south of the sub-tropical high play an important role on the rainfall case.2) Low Level Jet (LLJ) transports vapor significantly, and there is always a moist-tongue, northwest of which the heavy rainfall occurs. As far as the whole troposphere layer is concerned, vapor mainly comes from the southwestern current and the low-pressure system on the sub-tropical ocean.3) Concerning this case, it advances an conceptive model of baroclinic systems development during the North-China rainstorm on former basis. The model unveils some main mechanisms of the case including potential vorticity (PV) descending from upper-level and high latitude, low-level MPV climbing up and the dry intrusion. When air mass carrying high PV descends to strong baroclinic zone, vertical vorticity of the convective system increases rapidly which leads to vigorous development of the system. MPV climbing up also activates the system's vorticty increasing acutely. Dry intrusion boosts up thermal contrast of the system and environmental field, which accelerates convection of the system.4) This case has typical frontal characteristic, and there exist significant meso-scale precipitating systems. Apparent-heat-source and apparent-moist-sink in the meso-scale system have similar distribution, and it means that latent heat release is primary heat source of the system. At the mid- & low-level the system is heated and at the upper level it is cooled, which leads to unstable stratification.