Henan Province, The Spring Characteristics Of Stratiform Precipitation And Artificial Rainfall Conditions,

Two precipitation cases of large-scale stratiform cloud occurred during April 12-15 and May 10-12, 2000 in Henan province. The cloud and precipitation process was studied in detail by combining observational data analysis with numerical simulation of the mesoscale model MM5. The macro and micro physical characteristics of precipitable cloud system were analyzed with several kinds of data, including satellite cloud photograph, synoptic map, surface precipitation data, radar echoes, and the Particle Measurement Systems (PMS) data. The areas abounded with supercooled liquid water (SLW) were determined according to the PMS indices and distributing characteristics of these areas were analyzed along the flight line. The macro and micro physical characteristics of cloud system was also simulated with the Fifth-Generation NCAR / Penn State Mesoscale Model (MM5) in this paper.The following conclusions were drawn by analyzing the observational data. The stratiform cloud system in Henan province distributed unevenly. There was a band-shape gap between two clouds and ununiformity also appeared inside the cloud bands. Concentration of the cloud particle and the ice particle was observed with the PMS and transformation of the concentration constituted a wavelike shape. Several modes of cloud particles exist probably in the cloud. Cloud particles existed in different modes in most area of the cloud while there was only one cloud particle mode in some area. Particle increasing area and particle decreasing area distributed alternately in the vertical direction.Distributing of the areas abounded with SLW is an important microphysical characteristic in the filed operation of precipitation stimulation. Position of the areas abounded with SLW in the radar echoes and developing phases of the cloud were analyzed. 11 areas abounded with SLW were determined in two precipitation cases. Wide spectrums of the cloud particles and many big cloud particles were found in the areas abounded with SLW.Distributing of the hydrometeors simulated by MM5 model was analyzed. There was a well corresponded relationship between the area with plenty of graupel particles and the area abounded with raindrop. And there was a well corresponded relationship between areas with plenty of snow and large area of high radar echo. There was scarce cloud Liquid Water Content (LWC) in the area corresponded with high radar echoes while much LWC existed in the area corresponded with low radar echoes and no radar echoes.Vertical distributing of the hydrometeors over certain spot simulated by MM5 model was also analyzed. The precipitation is composed of ice particles in the upper altitude, snow, graupel, raindrops and the cloud liquid water in the lower altitude. High radar echoes corresponded to areas with plenty of graupel and snow upon the zero centigrade line. Areas with plenty of raindrops corresponded to high radar echoes below the zero line. Warm cloud process was inapparent in some areas of the cloud due to the absence of cloud LWC in the lower altitude.