| Making the most use of NCEP data, conventional and non-conventional observation data, such as auto-rainfall station, Doppler radar, satellite cloud image, sounding data and numerical model, the torrential rainfall occurred from 22 to 23 June 2004 over western and northern Hunan province and from 29 June to 5 July 2006 over Jianghuai district was carefully studied. The paper reason out the large-scale environmental surrounding, environmental distinction and the dynamic mechanism by analyzing observation data and studied the developing feature of torrential rainfall cloud cluster, precipitation mechanism and micro-physical feature by utilizing a 2D cloud-resolving model. The Impact of ice microphysics and wind shear on rainfall are examined by analysis two sensitive experiments.The outcome showed that under the blocking pattern, the northwest flow associated with the Northeast China cold vortex and the warm and humid flow located to the south of the Southwest China constructed a convergence zone, in which MCS continued to form and propagate, causing torrential rainfall in Hunan province. The comparison in surface rain rate and reflectivity between the simulation and observations shows a good agreement.The 37-hour data are further categorized into the onset, mature, and decay stages using the difference between the domain-mean surface rain rate and its 37-hour mean. The results show: Vapor convergence rates during the onset and mature stages are similar in time- and domain-mean as well as in both raining stratiform and convective regions. the onset stage characterized as the fastest growth of cloud water and the evaporation of raindrop; The change of time- and domain-mean local vapor from a gain in the onset stage to a loss in the mature stage, and the significant reduction of time- and domain-mean local hydrometeor gain from the onset stage to the mature stage lead to the significant increase of time- and domain-mean surface rain rate from the onset stage to the mature stage although the time- and domain-mean vapor convergence rate is smaller in the mature stage than in the onset stage. The growth of cloud water by the condensation and cloud ice by deposition of supersaturated vapor in mature stage is as 2 and 3 times as ones in onset stage respectively, which is the main reason for the growth of rain; The time- and domain-mean surface rain rate decreases from the mature stage to the decay stage mainly because the time- and domain-mean vapor convergence weakens in the decay stage. The water condensation rate is only 1/4 as one in the mature stage and the rain collecting of water is weakest during the rainfall process. The source of ice is exhausted in the stage.As to the torrential rainfall event occurred from 29 June to 5 July 2006 over Jianghuai district, cold air come down due to twice adjustment of synoptic situation of a ridge sandwiched by two troughs in the mid and lower troposphere and deep southwest airflow is transported into south and east China. The clod and warm flow construct a convergence zone at 30~35°N , causing the torrential rainfall. The rainfall process occurred from 1200LST 29 June to 1800 LST 29 June, 0200 LST 30 June to 0800 LST 1 July, 1000 LST 2 July to 05LST 3 July, 0000 LST 4 July to 2200 LST 4 July 2006 is named as A, B, C and D respectively by the time and feature of the rainfall. The outcome shows: the rainfall of A. B, C is characterized as that convective rainfall amount takes 50% of the domain-mean rainfall amount and vapor convergence is main factor affecting the surface rainfall rate. The A is consisted of lots of short life span convection. Its local vapor loss, vapor divergence and local hydrometer change rate are larger than B and C in raining area. The rainfall of D is characterized as stratiform rain and its surface rainfall rate is come from the local vapor loss. The micro-physical distinction is list as blow: The growth rate of cloud water by the condensation of A, B, C is 1/5 as the cloud ice growth rate deposition of supersaturated vapor. The growth of raindrops mainly comes from collection of cloud water and melting of graupel and difference between the two micro-physic processes is about 20%. The growth rate of cloud water by the condensation of D is 64% as the cloud ice growth rate deposition of supersaturated vapor. The growth rate of raindrops by collection of cloud water is 30% less than the rate by melting of graupel. The evaporation rate of rainfall B is the slowest and the growth rate of graupel of rainfall A is the fastest in the rainfall process.Two sensitive experiments are carried out to check the impacts of ice microphysics and vertical wind shear on rainfall using the same forcing data as control run. The compared analysis between the ice microphysics experiment and the control experiment shows: Without ice microphysics, the temperature difference due to condensational heating is lower above 500hPa and higher below 500hPa, while the temperature due to radiative heating is higher above 300hPa. The condensation is the main factor to affect the differences of specific humidity. The temperature and moisture changes are depended on the rainfall process; With the changing of the coverage of raining convective and stratiform region, the vapor convergence and local vapor gain, which changed mostly, lead to the change of the surface rainfall rate; The simulated cloud top and the strongest reflectivity height is lower and intense of the strongest reflectivity is weaker.Without the vertical shear, the range of rainfall time and area changed mostly. The propagation velocity of the rainfall get slower and the life span get shorter, especially for the continuously east propagation rainfall; the simulated cloud top and the strongest reflectivity height is higher and the intense of the strongest reflectivity is weaker. It has weak impact on the temperature and moisture state.
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