Examining Lake-Effect Changes Across the Great Lakes in a Warming World Utilizing Dynamically Downscaled Climate Simulations

The Great Lakes are home to one of the most unique mesoscale phenomena with lake-effect precipitation bands that often form in the boreal cold season under ideal conditions, such as low wind shear and colder air moving over the relatively warmer lakes. These lake-effect bands are notorious for extreme whiteout conditions, high snowfall accumulations, and localized impacts to travel and economies across the region. Thus, they are important to study for prediction purposes and in the context of climate change. One question to examine is how lake-effect precipitation may evolve with the Earth’s changing climate. Previous challenges in conducting studies such as this include the expensive computing resources needed to resolve such small-scale phenomena as well as the large amount of data that would need to be analyzed and processed. Global climate models (GCMs) are currently too coarse to resolve mesoscale processes, such as lake-effect, warranting the need for downscaling efforts to more accurately resolve the relevant process.

This study examines new data from a high-resolution dynamically downscaled GCM generated by Gensini et al. (2022) over the contiguous United States. These new data provide a resolution sufficient to explicitly resolve convective processes, such as those pertinent for lake-effect precipitation, and can be used to quantify spatial and temporal changes in lake-effect snow processes. Two 15-year periods of data are examined, consisting of historical (1990-2005) and potential end-of-century (2085-2100) conditions under the RCP 8.5 climate scenario. Analysis is performed to identify changes in the background synoptic and mesoscale conditions conducive for lake-effect snow, such as mid-level flow and temperatures. Frequencies of precipitation type and amount over the Great Lakes are also examined to determine changes in snowfall and rainfall in a warming climate. The model output is finally compared to observations at representative sites across the Great Lakes region to ascertain local changes in temperature and cumulative precipitation by the end of the current century, as well as to determine lake-specific responses to a warming climate.