Downstream Evolution and Coastal-to-Inland Transition of Landfalling Lake-Effect Systems

Abstract

The distribution and intensity of lake- and sea-effect (hereafter lake-effect) precipitation are strongly influenced by the mode of landfalling lake-effect systems. Here, we used idealized large-eddy simulations to investigate the downstream evolution and coastal-to-inland transition of two lake-effect modes: 1) a long-lake-axis-parallel (LLAP) band generated by an oval body of water (hereafter lake; e.g., Lake Ontario) and 2) broad-coverage, open-cell convection generated by an open lake (e.g., Sea of Japan).Under identical atmospheric conditions and lake-surface temperatures, the oval lake generates a LLAP band with heavy precipitation along the mid-lake axis, whereas the open lake generates broad-coverage, open-cell convection with widespread, light accumulations. Over the oval lake, the LLAP band features a thermally forced and diabatically enhanced cross-band secondary circulation with convergence and ascent over the mid-lake axis. Downstream of the lake, flanking airstreams that avoid lake modification merge beneath the band where they experience sublimational cooling, producing a cold pool. At the upstream edge of the cold pool, a coastal baroclinic zone forms. Above this zone, ascent and hydrometeor mass growth are maximized, resulting in an inland precipitation maximum due to subsequent hydrometeor transport and fallout. Over the open lake, individual open cells grow larger and stronger with over-water extent, but a convective-to-stratiform transition begins at the coast. Here, convective vigor decays, mesoscale ascent begins, and enhanced hydrometeor growth results in an inland precipitation maximum. These results highlight variations in the coastal-to-inland transition of lake-effect systems that ultimately influence the distribution and intensity of lake-effect precipitation.

Development of a Polar Mesocyclone and Associated Environmental Characteristics During the Heavy Snowfall Event in Sapporo, Japan, in Early February 2022

“…The northern coastal region of Japan is among the areas of the world most affected by severe snowfall (Steenburgh & Nakai, 2020) due to the cold winter monsoonal wind that blows over the Sea of Japan and receives abundant moisture and heat from the ocean. This process, also observed around the Great Lakes of North America, is commonly referred to as sea‐ or lake‐effect precipitation and has been the subject of many previous studies (e.g., Gowan et al., 2021, 2022; Hjelmfelt, 1990; West et al., 2019).…”

Impacts of Historical Atmospheric and Oceanic Warming on Heavy Snowfall in December 2020 in Japan

“…Cumulonimbus clouds developing over the Sea of Japan move to the Japanese archipelago and bring much snowfall to the Sea of Japan coast (Steenburgh & Nakai, 2020). This mechanism is called as sea‐effect snowfall (Veals et al., 2019, 2020) and is similar to the lake effect that causes snowfall on the lee side of the Great Lakes and Great Salt Lake in North America (Burnett et al., 2003; Gowan et al., 2021; Hjelmfelt, 1990; Steenburgh et al., 2000; Steiger et al., 2013). In addition, the topographic uplifting maintains heavy snowfall on the windward side of the mountain ranges facing the Sea of Japan, which is a typical mountain heavy snowfall pattern in Japan (Akiyama, 1981a, 1981b; Iwamoto et al., 2008; West et al., 2019; Yamazaki et al., 2019).…”