Numerical Simulation of the Local Circulation of Complex Topography on the Gaoligong Mountains

In this paper, the mesoscale weather research and forecasting (WRF) model is used to simulate mountain-valley wind circulation in the region of south Gaoligong Mountains in the dry and wet seasons, in 2016, respectively. The applicability of five layer parameterization schemes (YSU, MYJ, MYNN3, ACM2 and BouLac) under complex underlying surface of the Gaoligong Mountains is compared. The results show that the YSU scheme performs best in temperature simulation. The mean absolute error of wind speed simulated by the ACM2 scheme is the smallest, and the absolute error of wind direction simulated by the MYNN3 scheme is the smallest. The diurnal variation of wind direction simulated by the YSU and MYJ schemes is more consistent with the observation. Valley wind circulation in the southern Gaoligong Mountains appears at 0900 BJT and turns to mountain wind circulation at 1900 BJT. Southerly wind mostly prevails in the daytime and northerly and westerly wind at night. During the day, the airflow converges at the top of the mountain and diverges in the valley. At night, it is opposite. The wind speed in daytime is greater than that at night. In the dry season, the west wind is weak, which is conducive to the development of local circulation in the lower troposphere. In the wet season, the eastward background wind is strong, suppressing the development of local circulation; thus, the height of the boundary layer is shorter than that in the dry season. In the dry season, the westerly wind meets the Gaoligong Mountains, sinks on the west slope, and forms vortices, and then the turbulence on the west side is well mixed, leading to a deep boundary layer. In the wet season, the easterly wind weakens the valley wind on the west side of Gaoligong Mountains, and the height of the boundary layer between Tengchong and Baoshan is similar.