ABSTRACT

Using a synoptic classification technique and gridded snow dataset, snowfall was evaluated in the eastern Great Lakes region from 1950-2009 during atmospheric conditions suitable for the development of lake-effect snow. Specific emphases were placed on detailing the long-term changes to snowfall magnitude and frequency, and quantifying changes in the contribution of total snowfall from lake-effect synoptic types. For Lakes Erie and Ontario, snowfall from lake-effect synoptic types represented approximately 48% of total snowfall, and 42% of snowfall days are synoptically lake-effect in nature. Over time, the percentage of total early-season snowfall from lake-effect synoptic types significantly increased downwind of the Lakes, by approximately 0.4% yr^-1, corresponding to an increase from approximately 40% lake-effect in the 1950s, to over 60% in the 2000s. This was due, in part, to changes in the frequency of snowfall-producing synoptic types, decreases in the percentage of precipitation falling as snow during non-lake-effect events, and increases in the magnitude of snowfall per lake-effect event. Changes in the proportion of total snowfall from lake-effect processes carries implications to water resources due to differences in snow-water-equivalent between lake-effect snow and snowfall from other mechanisms, such as mid-latitude cyclones.

摘要

使用天气分类技术和网格雪数据集，评估了 1950 年至 2009 年在适合湖泊效应雪发展的大气条件下五大湖区东部的降雪量。特别强调详细说明降雪量级和频率的长期变化，并量化湖泊效应天气类型对总降雪贡献的变化。对于伊利湖和安大略湖，湖效应天气类型的降雪约占总降雪量的 48%，42% 的降雪天数是自然天气湖效应。随着时间的推移，湖泊效应天气类型的初季降雪总量在湖泊顺风区显着增加，年均增加约 0.4% ^-1，对应于从 1950 年代约 40% 的湖泊效应增加到 2000 年代的 60% 以上。这部分是由于产生降雪的天气类型频率的变化，在非湖效应事件期间降雪的降水百分比下降，以及每个湖效应事件的降雪量增加。由于湖泊效应降雪与其他机制（如中纬度气旋）降雪之间的雪水当量差异，湖泊效应过程造成的总降雪量比例的变化对水资源产生影响。