Sensitivity of Lake-Effect Convection to the Lake Surface Temperature over Poyang Lake in China

In this study, high-resolution weather research and forecasting (WRF) simulations are used to explore the sensitivity of lake-effect convection over Poyang Lake (PL) to the change of lake surface temperature (LST). A control experiment (CTR) with climate mean LST (303 K) is compared with six sensitivity experiments (CTR−1/2/3K and CTR+1/2/3K) in which the LSTs are set based on the mean LST difference of 6 K between the maximum and mini-mum. The results show that the CTR experiment reasonably reproduces the lake-effect convection, and the lake-effect convection in sensitivity experiments is significantly influenced by the LST. With the increase of LST, the initiation time of the lake-effect convection is advanced gradually, while the initiation location moves PL from its shore. The lake-effect convection strengthens (weakens) in the increase-temperature CTR+1/2/3K (decrease-temperature CTR−1/2/3K) experiments, but the lake-effect convection does not monotonically strengthen with the LST, for the strongest one occurring in the CTR+1K experiment. The corresponding diagnostic analysis shows that the upward sensible heat flux and latent heat flux over PL increase with the LST, resulting in the enhancement of the lake–land breeze and the enlargement of the convective available potential energy (CAPE). This is the main reason for the changes in the initiation time and location, as well as the intensity of lake-effect convection in different experiments. In addition, the non-monotonous variation of the level of free convection, which is mainly induced by the non-monotonous variation of the lifting condensation level, is responsible for the non-monotonous variation of the lake-effect convection intensity with the LST.