Studies Of Cloud And Vapor Flux And Short-middle-range Forecasting On Cloud Cover In Summer Over The Northeast Of Qinghai-tibet Plateau

It’s well known that clouds are an important weather phenomenon and the necessary condition of precipitation; it is not only climate system’s internal parameters, but also represents the wet conditions and vertical movement of atmosphere. The transport and convergence of water vapor is an important condition for cloud’s formation. In the great western development, with the development of industry and agriculture production and people’s needs, water shortages become more and more serious, so artificial precipitation-enhancement is an efficient approach to make use of water-cloud resources in the air and lighten water resources shortage. The Northeast of Qinghai-Tibet Plateau is the transitional zone from Qinghai-Tibet Plateau to Loess Plateau, and the agriculture and animal husbandry. At the same time this area has complex terrain, often is affected by a variety of weather systems, and it is very sensitive to climate change. Therefore, analysis in water-cloud characteristics, trends of climate change and establishment cloud forecast of Northeast of Qinghai-Tibet Plateau has an important significance in enhancing understanding of the characteristics and climate changes of Qinghai-Tibet Plateau. Meanwhile, it has a great significance on artificial precipitation-enhancement and makes use of water cloud resource in the air.Based on daily data from observational stations, NCEP reanalysis data and T213L31historical data in the Northeast of Qinghai-Tibet Plateau, the developing characteristics of cloud and the relationship with the vapor flux in the northeast of Qinghai-Tibet Plateau are studied in terms of the statistical analysis, the HYSPLIT₄Model and support vector machine （SVM） method. Also a software includes a set of data database and a forecasting method of cloud cover in this area is established. The results showed that:（1） There is a growing tendency of the amount of total cloud and low cloud in the overall presentation from2001to2011, especially in spring and summer. The probability of convective cloud is higher than nonconvective cloud in the northeast of Qinghai-Tibet Plateau. Clouds to be helpful for artificial rain decreased obviously year by year.（2） The average precipitation amount over the region decreases from the south to the north. Water vapor content decreases from southeast to northwest. And the spatial distribution of water vapor content has a big change gradient in the southeast region.（3） Water vapor content over Maqu region mainly below400hPa, the maximum layer is surface to600hPa, then600-500hPa, and then decreasing gradually with height in May to October. According to analysis of the83’s water vapor trajectory of heavy rain cases from1967to2010found that there are two conveyor belts; it is respectively the South Asian monsoon belt of water vapor conveyor belt in higher layer and the East Asian monsoon belt of water vapor conveyor belt in lower layer.（4） Through using SVM method and T213L31’s data, gives an effective method which can forecast cloud cover. With the forecast time extension, prediction accuracy rate showed a downward trend; and forecast accuracy of1-10days has a good result, between60%-80%.（5）For having a better service in meteorological data inquires and artificial precipitation-enhancement in this area, a software which includes a set of data database and a forecast method of cloud cover in this area is established. The powerful functions of the software are as following:getting the meteorological data information by click on the map site, managing the meteorological data, displaying the prediction results of cloud cover in the screen and so on.