Impacts of Lake Surface Temperature on Atmosphere Over the Great Lakes Region

The Great Lakes substantially influence the regional weather and climate by impacting the heat and water budget. While there are many previous studies investigated the snowstorms affected by the lakes, this study examines the impacts of a more accurate lake surface temperature (LST) on atmosphere that can potentially change summer precipitation as well. In particular, we design a set of twin experiments: in Experiment #1, the WRF model utilizes the default SST from ERA5 as its lower boundary condition over the Great Lakes; in Experiment #2, everything is the same as #1, except that the SST over Great Lakes is replaced with daily GLSEA LSTs, derived from Advanced Very HighResolution Radiometer onboard polarorbiting satellites. To quantify the uncertainty and examine the robustness of the impacts of this LST effect, we conduct 10 ensemble members for each experiment by initializing the model at different times. Results show that the more accurate LST (usually is warmer than the default SST) over Great Lakes (1) warms up the near surface air temperature by 2-4 degK; (2) increases the moisture available over the Great Lakes Basin and the surrounding lands especially over the south and east of the lakes; (3) promotes a more unstable convective environment which is favored by convection development and precipitation formation.