Influence of lake breezes on the triggering of moist convection on the Tibetan Plateau: A large-eddy simulation study

Abstract

Abstract Applying 1-D surface heterogeneity and observed atmospheric vertical profiles as initial conditions, two sets of large-eddy simulation experiments provided insight into the influence of lake size and soil moisture on the development of lake breezes and moist convection over land beside the lake. When the lake diameter increased from 20 km to 50 km and 70 km, the maximum precipitation increased by 71.4% and 1.29 times, respectively. There are two reasons for larger precipitation over land in large-lake simulations: 1. Stronger and broader updrafts were found near the lake breeze front (LBF); 2. The air at 2–4 km was moister, probably because more water vapor below 2 km was advected by the lake breezes and transported upward through turbulent exchange. Moreover, When the lake diameter increased from 20 km to more than 50 km, the deep moist convection (DMC) occurred 20 minutes earlier. This may be related to broader shallow convective cloud and larger vertical velocity of cloud-initiating parcels in large-lake simulations. Shallow moist convection transitioned to DMC earlier with broader clouds under moderate and high soil moisture conditions. Notably, stronger and broader updrafts near the LBFs, along with the advection of moisture induced by the lake breezes, caused the shallow moist convection to reach its peak 1 hour earlier in the driest soil moisture case. However, smaller evapotranspiration could not provide sufficient moisture for the development of DMC. Our simulation results show that lake breeze circulations are essential for the development of moist convections in lake region.