The phase state of precipitation in winter is relatively complex, and the consistency of transformation forecast between liquid and solid state is a difficulty in the forecast. In order to explore the application of muti-source data in rain-snow phase prediction, the precipitation phase characteristics of a rain-snow weather in Zhangjiakou area from 17 to 19 November 2020 were analyzed based on ERA5 reanalysis data, as well as cloud radar, microwave radiometer and SA dual polarization Doppler radar observation data. The results show that the rain-snow weather occurred under the coordination of upper trough, lower vortex and surface trough, the cold air from northwest behind the upper trough moved southward, which led to a rapid drop of air temperature and the change of precipitation phase. In the early stage of the process, the whole atmosphere was strong warm advection, and the ground temperature was high and the precipitation phase was rain. In the evening of November 18, the cold advection developed strongly, the temperature of each layer decreased rapidly, and the whole layer turned into cold layer, which led to the conversion of precipitation phase to snow. Through the dynamic diagnosis of divergence and vertical velocity, it was shown that the dynamic forcing during the rainfall period was mainly located in the upper layer, while during the snowfall period it was mainly located in the lower layer. The high-resolution data of cloud radar could reflect the change of 0 ℃ layer, and the change of mass center greater than 10 dBZ could indicate the change of precipitation intensity. The maximum basic velocity could reach 6-8 m·s^-1 during rainfall stage, while it was less than 2 m·s^-1 at snow stage. The high-resolution data of microwave radiometer could accurately judge the time of rain-snow conversion, and it was found that the integral water vapor appeared jump and peak value three to five hours before the precipitation. The combination of dual polarization radar and microwave radiometer could accurately judge the phase of precipitation particles, which could be used in prediction of precipitation phase.

Based on ERA reanalysis data during 1979-2017, the spatial-temporal variation characteristics of surface sensible and latent heat flux in Southwest China were analyzed by using empirical orthogonal function (EOF) and power spectrum methods. The results are as follows: (1) In Southwest China, the sensible heat flux in spring was larger than that in summer, while latent heat flux was larger in summer than in spring. The sensible heat flux in spring and summer began to weaken after 2000, while the latent heat flux in spring and summer had increased significantly since 2000. (2) There were three spatial patterns of sensible heat flux in spring, which were mainly characterized by east-west reverse, region-wide uniform and negative and positive dipole spatial distribution. There were mainly two spatial patterns in summer, which showed the consistency of spatial distribution. The corresponding time coefficients characterized the significant inter-decadal and inter-annual periodic variations of sensible heat fluxes in summer. There were three spatial patterns of latent heat flux in spring, which were mainly characterized by uniform region-wide, reverse east-west and decreasing outward in all directions from the center. There were mainly two spatial patterns of latent heat flux in summer. The first mode characterized the consistency in spatial distribution. The second mode indicated that the flux increased gradually from northwest to southeast in a trapezoidal manner. The change of corresponding time coefficients characterized that latent heat flux in spring and summer had significant inter-annual and inter-decadal variation characteristics. The sensible heat fluxes in spring and summer were characterized by inter-annual variations about 3 years and inter-decadal variations more than 10 years, and inter-decadal variations were stronger than inter-annual variations. The latent heat flux in spring and summer mainly had inter-decadal variations over 10 years in Southwest China.

After deducing external trajectory calculation method under non-standard atmospheric conditions for 37 mm anti-aircraft gun, which was widely used in the field of weather modification, the ballistic data in uniform cross wind and range wind field were simulated. The results show that the wind made a great influence on the flight path of projectile. The range wind can change the ballistic range by affecting the size and direction of air resistance. The cross wind can generate a lateral deviation of the trajectory along the wind by affecting the direction of the air resistance. On the same launch elevation angle, with the change of wind speed, the trajectory deviation correction caused by cross wind and the range correction caused by range wind showed a variation law that was similar to arithmetic progression. Through fitting analysis, the relationship among wind speed, elevation and trajectory correction was obtained，which can be used to estimate trajectory correction under arbitrary wind speed in actual operation.