1.Key Laboratory for Cloud Physics of China Meteorological Administration,Chinese Academy of Meteorological Sciences;2.Ningxia Key Laboratory of Meteorological Disaster Prevention and Reduction
To develop atmospheric water resources reasonably over the Liupan Mountain area based on precipitation enhancement techniques, it is necessary to understand firstly the influence of water vapor field and topography on local precipitation, the characteristics of water resources in the air and the hydrometeor precipitation efficiency of clouds in typical precipitation processes over this area. Based on the high spatial and temporal resolution reanalysis dataset issued by the European Centre for Medium-Range Weather Forecasts(ECMWF) and the moderate resolution imaging spectrometer (MODIS) data, the features of water vapor transport, the convergence and ascending motion of water vapor flux forced by topography, as well as orographic cloud characteristics are investigated using statistical analysis methods. Besides, during several precipitation events with stratus clouds embedded in convective systems moving from west to east in the summer of 2016 and 2017, the hydrometeor precipitation efficiency is calculated based on the simulation results of WRF model and ERA5 reanalysis dataset respectively. Results are as follows. In the east of Northwest China, there are abundant atmospheric precipitable water and stronger water vapor transport over Liupan Mountain area. Affected by the Asian monsoon, abundant water vapor is transported by the southerly wind into this area in summer, which makes the mountain area become a higher relative humidity zone. The clouds fraction(CF) reaches 70% over the Liupan Mountain in the afternoon of spring, summer and autumn, and the cloud water path (CWP) and the optical thickness (COT) in summer are significantly larger than those over the surrounding areas. The dynamic field caused by topography has a significant impact on summer precipitation. Obvious convergence and ascending motion of water vapor flux forced by topography occurs in the process with daily precipitation exceeding 5mm, and the more intense the convergence and ascending motion is, the stronger the corresponding rainfall intensity is. In the typical precipitation systems in summer, the average hydrometeor precipitation efficiency is about 48.1% and much of the hydrometeor in the air fails to become precipitation. Therefore, as a source of water conservation, the Liupan Mountain area has relatively abundant atmospheric water resources but insufficient precipitation in summer, which means certain potential in this area for developing the atmospheric water resources.