Numerical Simulation of Physical Process of Precipitation Intensity Weakening in Poyang Lake
In order to quantitatively analyze the influence of lake on the intensity and properties of precipitation, this paper designes the control experiment and the sensitivity experiment of lake land-surface, based on the mesoscale numerical model of WRF3.8 version and the NCEP/NCAR FNL 1°×1° analysis data with time interval of 6 h. The high value center of heavy precipitation near Poyang Lake from 14 to 15 June 2011 is analyzed. The results show that the surface of Poyang Lake is a “cold source” during the day, which has obvious “cooling” regulation effect on the horizontal range of 100 km and the vertical range of 800 m. This weakening of thermal conditions affects the intensity and durability of the vertical upward motion in the middle and lower troposphere, 〖JP2〗resulting in reduced precipi-〖JP〗tation intensity and shorter precipita-tion duration, which ultimately reduces about 10% of accumulated rainfall near the lake. The underlying surface of Poyang Lake can only improve the saturation degree (relative humidity) of atmospheric water vapor in the boundary layer, but “reduce” the absolute content of water vapor (specific humidity), which is one of the reasons why the sensitivity experiment rather than control experiment precipitation center has greater strength and a wider range of heavy precipitation after lake land-surface. The lower surface of the lake water body results from reducing the atmospheric temperature and absolute humidity of the boundary layer so that the atmosphere has a weaker convection effective potential energy than sensitivity experiment, and the lower atmosphere (1 〖KG-*5〗000-850 hPa) has a weaker convection instability. Sounding reflects the control experiment near the formation has a shallow inverse temperature structure. It has a lower CAPE than the lake terrestrial sensitivity experiment, and finally weakens the convection properties of the control experiment precipitation. Generally speaking, the underlying surface of Poyang Lake changes the temperature and absolute humidity of the boundary layer, thus changing the environmental conditions of the lower atmosphere, and affecting the temperature and humidity conditions of the initial uplift gas block, delaying and weakening the duration and intensity of vertical motion, weakening the convection in the lower layer near the lake, and having a 45% inhibition rate on atmospheric heating, ultimately reducing the intensity and range of precipitation.