Contributions of Lake-Effect Periods to the Cool-Season Hydroclimate of the Great Salt Lake Basin

Although smaller lakes are known to produce lake-effect precipitation, their influence on the precipitation climatology of lake-effect regions remains poorly documented. This study examines the contribution of lake-effect periods (LEPs) to the 1998–2009 cool-season (16 Sep – 15 May) hydroclimate in the region surrounding the Great Salt Lake, a meso-β-scale hypersaline lake in northern Utah. LEPs are identified subjectively from radar imagery, with precipitation (snow-water equivalent) quantified through the disaggregation of daily (i.e., 24-h) COOP and SNOTEL observations using radar-derived precipitation estimates. An evaluation at valley and mountain stations with reliable hourly precipitation-gauge observations demonstrates that the disaggregation method works well for estimating LEP precipitation, with some random error during shorter, hourly periods.

During the study period, LEPs account for up to 8.4% of the total cool-season precipitation in the Great Salt Lake Basin, with the largest contribution to the south and east of the Great Salt Lake. The mean monthly distribution of LEP precipitation is bimodal, with a primary maximum from Oct–Nov and a secondary maximum from Mar–Apr. LEP precipitation is highly variable between cool seasons and strongly influenced by a small number of intense events. For example, at a lowland (mountain) station in the lake-effect precipitation belt southeast of the Great Salt Lake, just 12 (13) events produce 50% of the LEP precipitation. Although these results suggest that LEPs contribute modestly to the hydroclimate of the Great Salt Lake basin, infrequent but intense events have a profound impact during some cool seasons.