The Developing Structure of a Black Storm and Its Numerical Experiment of Different Model Resolution
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摘要: 1993年5月4~6日在我国西北部地区发生了一次“黑风暴”。用改进的MM1和高分辨PBL参数化及40 km细网格控制试验能基本上模拟出“93.5”黑风暴的结构和演变。模拟结果表明,黑风暴发展时段,在PBL内与一个中尺度气旋性强涡旋相伴,在对流层内与一个垂直涡柱相伴。这个伸展至对流层顶的涡柱下(上)半部是与低(高)空强烈辐合(辐散)入(外)流相伴的气旋(反气旋)性涡柱。该黑风暴结构不同于一般锋面结构,其主要判别是:界面坡度陡,θe水平梯度大,斜压性强,PBL内暖心明显。该暖心结构与下垫面剧烈热力强迫有关。不Abstract: The developing structure and evolution of a black storm occurred in the northwest region of China from 4 to 6 May 1993 (“93.5”) can be basically simulated by using a control experiment of the improved MM4 model with high resolution PBL parameterization and 40 km fine-mesh. The simulated results show that the black storm was associated with both a mesoscale cyclonic strong vortex in the PBL and a vertical vortex column in the troposphere during the developing stage. The lower (upper) part of this vortex column, stretching to the tropopause was cyclonic (anticyclonic) vortex column associated with intensive converence (divergence) inflow (outflow). According to the cross section of the equivatlent potential temperature, the major differences of the structure of the black storm from that of black storm from of general front are: the steep slope of the boundary surfaces, the large horizontal gradient of θe, the quite intensive baroclinity, the obvious warm-core in the PBL. The warm-cored structure in the lower part of the black storm was related to intensive thermal over underlying surface. The comparison experiments of the different PBL parameterization and model spatial resolutions show that it would be necessary to enhance the spatial resolution of the mesoscale numerical model and to adopt a better PBL parameterized scheme in order to improve the simulation of the developing structure and evolution of black storm.
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Key words:
- Black storm;
- Numerical simulation;
- PBL parameterization;
- Model resolution
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