How lake breezes impact convection on the Tibetan Plateau: A large-eddy simulation study

Abstract

Lake breezes are verified to play an important role in atmospheric boundary-layer development, convection triggering, and the transition from shallow to deep convection. The Tibetan Plateau (TP), known as the “Asian water tower”, contains more than 50% of China’s lakes in terms of area. In his study, we investigated the convection development in summer afternoons over lakeside land on the TP, the interaction between lake breezes and shallow convection triggering, the effect of lake diameter on the transition from shallow to deep convection, and the mechanism of soil moisture changes in lakeside land affecting the convection development. Using the WRF-LES model, which couples the lake model and land surface model in an idealized configuration, we performed two sets of idealized simulations with varying lake diameter and soil moisture content in the WRF-LES and found that: 1) larger lakes produce stronger lake breeze circulations and more moisture is advected from the lake to the lakeside land and lifted, creating wetter and boarder shallow convective clouds which accelerating the transition to deep convection; 2) The dryer soil induces stronger lake breeze circulations, which is beneficial for lifting the air parcels and generating moisture advection to maintain shallow convection over the lakeside land; 3) However, shallow convective clouds cannot be moistened and widened and develop into deep convection without sufficient evaporation from the ground surface in dry soil moisture conditions. Our simulation results highlight the importance of the horizontal and vertical transport of moisture by the lake breeze circulations in moistening and broadening shallow convective clouds and developing into deep convections.