Examining Lake-Effect Changes Across the Great Lakes Utilizing Dynamically Downscaled Climate Simulations

Abstract

The Laurentian Great Lakes are home to unique mesoscale lake-effect snow bands that often form in the boreal cold season under specific conditions and are notorious for extreme whiteout conditions, high snowfall accumulations, and localized impacts to travel and economics across the region. The electrification of lake-effect snow bands via locally intense convection can produce thundersnow, creating potential hazards for infrastructure and those outside. These events develop under temperature, wind speed and shear, and instability conditions, which are expected to change in a warming climate. Thus, it is important to understand how climate change could impact lake-effect precipitation. General circulation models (GCMs), which are the primary tools used to study climate change and its impacts on weather systems, are currently too coarse to resolve mesoscale processes, such as lake-effect precipitation, which has posed a challenge for prior studies. Downscaling of these GCM simulations is needed to more accurately resolve the relevant process. This study examines new data from a high-resolution dynamically downscaled GCM 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 end-of-century (2085-2100) conditions under the Representative Concentration Pathway (RCP) 8.5 climate scenario. It is found that snowfall from lake-effect snow events is expected to retain their intensity or even increase in intensity over certain parts of the region. The most intense lake-effect snowfalls are expected to become even more intense, especially off portions of Lake Superior and Lake Huron. This increase in intensity is due to increasing lake surface air temperatures and therefore lower-level instability for lake-effect bands to utilize, although the temperatures remain cold enough for precipitation to remain as snow. Owing to the increase in temperature, lake-effect snowfall occurrences are also more constrained to the core winter season and are expected to decrease by the end of the century. Likewise, continuous snowfall events are expected to produce more snowfall on average while becoming less common and slightly longer in duration. With increased low-level instability lake-effect snow bands are expected to become deeper and contain stronger updrafts, perhaps increasing the number of lake-effect electrification and thundersnow occurrences in a warming world.