Examining the Impact of Great Lakes’ Temperature Perturbations on Simulated Downwind Precipitation

Data from General Circulation Models (GCMs) may not be resolved at a scale that provides information about inland water bodies, but such features may be important when investigating regional climate changes. Temperatures for the North American Great Lakes must therefore be estimated when downscaling GCM data with a Regional Climate Model such as the Weather Research and Forecasting (WRF) model. Observational analyses conclude that the Great Lakes’ surface temperatures have been increasing faster than the surrounding air over the past few decades, particularly during the warm season, which is a trend that is expected to continue. Aside from running a lake model which can be difficult to parameterize, two commonly used metrics for estimating lake temperatures during WRF preprocessing—SSTs from the Atlantic Ocean and Hudson Bay, and temporally averaged over-lake air temperatures—may introduce large errors. For the present study, a sensitivity analysis is conducted to investigate the impacts of lake surface temperature perturbations from the 2010 – 2014 climatology on WRF-simulated precipitation over the Lake Champlain Basin. The Basin, which borders New York and Vermont directly downwind of the Great Lakes, is at the center of a 4-km resolution domain which is nested within two larger domains, the outermost of which is run with ERA-Interim data. Both of the larger domains encompass some or all of the Great Lakes. Here we explore whether higher lake temperatures, which produce greater evaporative losses, also produce significantly more precipitation within the central domain.