Through the observation and study of the raindrop spectrum, we can not only explore the evolution law of precipitation but also understand the microphysical characteristics of different types of precipitation clouds. This paper uses the raindrop spectrum data observed at Naqu Station, Yushu Station, Linzhi Station, and Emei Mount Station, as well as cloud radar data in the Yushu region in the Tibetan Plateau. Raindrop spectral characteristics are studied, and the raindrop size distribution (DSD) characteristics of the four stations are analyzed. The results are as follows: (1) The overall raindrop spectral concentration of the four stations decreases with the increase in particle size after the peak value. The downtrend is most gentle at the peak. (2) All rain intensity levels show the characteristics of multiple vertices. At Linzhi Station, Naqu Station and Yushu Station, the particles with a diameter of <1 mm contributed the most to the precipitation rate, while the particles with a diameter of <1 mm at Emei Mount Station contributed the least to the precipitation rate. (3) The precipitation in the central and eastern margins of the Tibetan Plateau is dominated by small and medium-sized particles, accounting for 95–99% of the precipitation particle number concentration. (4) The raindrop spectra of the three types of precipitation clouds at the four sites are all cumulonimbus precipitation Cumulonimbus in the uppermost layer, stratiform cloud precipitation stratiform cloud in the lowermost layer, and mixed cloud precipitation stratiform cloud in between. (5) Cloud radar analysis of precipitation structure shows that cumulonimbus and mixed clouds develop vigorously, and the highest cloud height can reach 13 km, but the average precipitation duration of mixed clouds is shorter than that of cumulonimbus; stratiform clouds develop relatively smoothly, with cloud heights of 6–7 km, the average precipitation duration is the shortest.

Changes in the surface fluxes cause changes in the annular flow field over a region, and they affect the transport of water vapor. To study the influence of the changes in the surface flux on the water vapor transport in the upper layer in the canyon area of southeastern Tibet, in this study, the water vapor transport characteristics were analyzed using the HYSPLIT_v4 backward trajectory model at Danka and Motuo stations in the canyons in the southeastern Tibetan Plateau from November 2018 to October 2019. Then, using ERA-5 reanalysis data from 1989 to 2019 and the characteristics of the high-altitude water vapor transportation, the impact of the surface flux changes on the water vapor transportation was analyzed using singular value decomposition (SVD). The results show that the main sources of the water vapor in the study area were from the west and southwest during the non-Asian monsoon (non-AMS), while there was mainly southwest air flow and a small amount of southeast air flow in the lower layer during the Asian monsoon (AMS) at the stations in southeastern Tibet. The water vapor transmission channel of the westward airflow is higher than 3000 m, and the water vapor transmission channel of the southwestward and southeastward airflow is about 2000 m. The sensible heat and latent heat are negatively correlated with water vapor flux divergence. The southwest boundary of southeastern Tibet is a key area affecting water vapor flux divergence. When the sensible heat and latent heat exhibit downward trends during the non-Asian monsoon season, the eastward water vapor flux exhibits an upward trend. During the Asian monsoon season, when the sensible heat and latent heat in southeastern Tibet increase as a whole, the eastward water vapor flux in the total-column of southeastern Tibet increases.

Mount Emei is located on the eastern edge of the Tibetan Plateau, on the transition zone between the main body of the Tibetan Plateau and the Sichuan Basin in China. It is not only the necessary place for the eastward movement of the plateau system but also the place where the southwest vortex begins to develop. Its special geographical location makes it particularly important to understand the turbulence characteristics and surface energy balance of this place. Based on the Atmospheric Boundary Layer (ABL) tower data, radiation observation data and surface flux data of Mount Emei station on the eastern edge of the Tibetan Plateau from December 2019 to February 2022, the components of surface equilibrium are estimated by the eddy correlation method and Thermal Diffusion Equation and Correction (TDEC) method, the characteristics of surface energy exchange in the Mount Emei area are analyzed, and the aerodynamic and thermodynamic parameters are estimated. The results show that the annual average value of zero-plane displacement $\mathrm{d}$ is 10.45 m, the annual average values of aerodynamic roughness $Z_{0m}$ and aerothermal roughness $Z_{0h}$ are 1.61 and 1.67 m, respectively, and the annual average values of momentum flux transport coefficient $C_D$ and sensible heat flux transport coefficient $C_H$ are $1.58\times {10}^{-2}$ and $3.79\times {10}^{-3}$, respectively. The dimensionless vertical wind fluctuation variance in the Mount Emei area under unstable conditions can better conform to the 1/3rd power law of the Monin–Obukhov similarity theory, while the dimensionless horizontal wind fluctuation variance under unstable lamination and the dimensionless 3D wind fluctuation variance under stable condition does not conform to this law. In the near-neutral case, the dimensionless velocity variance in the vertical direction in this area is 1.314. The daytime dominance of sensible and latent heat fluxes varied seasonally, with latent heat fluxes dominating in summer and sensible heat transport dominating in winter. he surface albedo of Mount Emei in four seasons is between 0.04 and 0.08. The surface albedo in summer and autumn is higher than that in Mount Emei. The influence of the underlying surface on surface reflectance is much greater than other factors, such as altitude, longitude and latitude. The non-closure phenomenon is significant in the Mount Emei area. The energy closure rates before and after considering canopy thermal storage are 46% and 48%, respectively. The possible reason for the energy non-closure in this area is that the influence of horizontal advection and vertical advection on the energy closure is not considered.