The Upper Reaches Of The Yellow River On The Characteristics Of Convective Precipitation In The Autumn Of Observation And Analysis And Numerical Simulation Study

in the river bason of Huanghe, it is in more and more serious shortageof water resources in these years. This situation did bring losses to theeconomic development of the areas along the Huanghe River, such as Qinghaiprovince, Ganshu province. In the autumn seasons of 2002 at Hennancounty (sea level elevation is 3500m)in Qinghai Province,a serices ofscientific rain-enhancement experiments had been carried out by the playof "scientific research of technique for precipitation enhancement" .Based on the data observed there, the feature of cloud precipitation hadbeen analyzed briefly in this paper. The main results are showed below:(1)During the rain-enhancement experiments, data of 100 conventionalobservation shows that frequency of low-level cloud is nearly 80percent at Henan county in the river bason of Huanghe, Cumulus is themost in low-level cloud, Cbcap often forms at 20 o' clock.(2)The observation of ice nuclei shows that the number contents of icenuclei in the upriver area of Huanghe is great than the results ofPeking in the 60s and Hebei in the 70s, It is less than Peking in the90s.(3)The observation of radar finds that the temperature of cloud base is so low, Cold cloud base is the most important feature. Bimodal distribution is the feature of frequency spectrum of echo depth, Two peak value is 6km and llkm(sea level elevation is 3.5km). (4)According to the analysis, cold rain process is much more important than warm rain process. The observation of raindrop size distribution shows that bimodal spectrum is the main spectrum distribution of precipitiong of Cbcap: the first peak value appears in little drop(diameter <0. 2mm), the second peak value often appears in l-3mm of diameter.(5)Base on the result of the numerical simulations of 3-D convective cloud model, the precipitation in experiment area was controlled by cold rain process and ice crystal is main source of graupel, which is produced by auto-conversion from ice crystal to graupel and then grow by collection with ice. Seeding Agl should be done before ice nucleus largely activated, so we can enhance rain fall by improving ice content, deleting super-cool water. If not, there will be large amount ice crystal growed in nature cloud, artificial nucleus would be nouseful.