Numerical Simulation of Local Circulation over the Cangshan Mountain-Erhai Lake Area in Dali, Southwest China

The characteristics of local circulation in autumn over Cangshan Mountain-Erhai Lake in Dali were simulated using the WRF_CLM model, which includes a lake module. Simulated near-surface temperature, wind speed, and wind direction by the WRF_CLM model show good agreement with the observation data. In autumn, valley breezes start at 0800 BT (Beijing Time) and end at 1700 BT, while lake breezes last from 0900 BT to 1900 BT. The local alp terrain and Erhai Lake have a large impact on the local circulation. Starting time of the mountain-valley breeze is 1 hour earlier than that of the lake-land breeze. Mountain and land breezes at night are stronger than valley and lake breezes in daytime. Valley and lake breezes cooperate, reaching up to 2600 m in height during the day, while lake-land circulation is weakened by mountain breezes from Cangshan at dusk. A cyclonic circulation is maintained by the combination of mountain breeze and land breeze in the south of the basin at night. The convective boundary layer develops quickly after sunrise, and reaches a peak height of 2000 m at 1700 BT, then decreases to 100 m at night over the land surface. The boundary layer height over the lake surface is 300 m lower at daytime than over the land surface and 100 m higher at night.