LAUSR

A convective storm crossing Poyang Lake (PL) in China during 1200-1600 UTC on 13 May 2015 is examined. The results show that this storm occurs ahead of a 500-hPa trough with weak low-level temperature advection and a convectively stable layer between 925 and 850 hPa, and the tail of the storm is enhanced when its spearhead sweeps over PL after the sunset. Due to the heating and moistening of PL, the convectively stable layer over PL is destabilized; and instead, a deep (below 700 hPa) convectively unstable layer is organized. Moreover, both the radiative cooling and the storm-induced cooling result in a rapid air (near-surface) and land temperature decrease in the surrounding areas. Thus, a large lake-land temperature difference (about 6°C) occurs, which is conducive to generating land-lake breeze and enhancing the convergence of the low-level wind. Finally, the PL-induced deep convectively unstable layer and the enhanced low-level convergence jointly strengthen the crossing storm. To further confirm this, two simulations (with or without PL) are conducted with the Weather Research and Forecast (WRF) model. The simulation with PL successfully reproduces the evolution of the storm crossing PL, while the simulation without PL fails. In the simulation with PL, a high θ se tongue at 850 hPa associated with the storm moves eastward and downward, and merges with the PL-induced lake boundary layer, forming a deep convectively unstable layer under 700 hPa. However, in the simulation without PL, the stable layer constantly maintains under 900 hPa. In addition, the 900-hPa wind difference between the simulations with and without PL shows a land-lake breeze circulation that strengths the convergence of the low-level wind.