Hindawi Advances in Meteorology Volume 2018, Article ID 5404123, 20 pages https://doi.org/10.1155/2018/5404123 Research Article Historical Spatiotemporal Trends in Snowfall Extremes over the Canadian Domain of the Great Lakes Basin Janine A. Baijnath-Rodino and Claude R. Duguay Department of Geography and Environmental Management and Interdisciplinary Centre on Climate Change, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1, Correspondence should be addressed to Janine A. Baijnath-Rodino; [email protected] Received 20 March 2018; Revised 1 August 2018; Accepted 18 October 2018; Published 10 December 2018 Academic Editor: Stefano Dietrich Copyright © 2018 Janine A. Baijnath-Rodino and Claude R. Duguay. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. *e Laurentian Great Lakes Basin (GLB) is prone to snowfall events developed from extratropical cyclones or lake-effect processes. Monitoring extreme snowfall trends in response to climate change is essential for sustainability and adaptation studies because climate change could significantly influence variability in precipitation during the 21st century. Many studies in- vestigating snowfall within the GLB have focused on specific case study events with apparent under examinations of regional extreme snowfall trends. *e current research explores the historical extremes in snowfall by assessing the intensity, frequency, and duration of snowfall within Ontario’s GLB. Spatiotemporal snowfall and precipitation trends are computed for the 1980 to 2015 period using Daymet (Version 3) monthly gridded interpolated datasets from the Oak Ridge National Laboratory. Results show that extreme snowfall intensity, frequency, and duration have significantly decreased, at the 90% confidence level, more so for the Canadian leeward shores of Lake Superior than that of Lake Huron, for the months of December and January. To help discern the spatiotemporal trends is snowfall extremes, several trend analyses for lake-induced predictor variables were analysed for two cities, Wawa and Wiarton, along the snowbelts of Lakes Superior and Huron, respectively. *ese variables include monthly maximum and minimum air temperature, maximum wind gust velocity, lake surface temperature, and maximum annual ice cover concentration. Resultant significant increase in December’s maximum and minimum air temperature for the city of Wawa may be a potential reason for the decreased extreme snowfall trends. 1. Introduction few hundred km in length and is triggered by turbulent energy and moisture fluxes off lakes [1]. During the winter season, heavy snowfall is a prominent *e shear spatial extent and geographic location of the meteorological phenomenon in the Great Lakes Basin (GLB) Laurentian Great Lakes make LES a prominent meteoro- and is derived from either extratropical cyclones or lake- logical phenomenon during the late autumn and winter induced snowfall processes. Extratropical cyclones are months [1]. LES forms when boundary layer convection is generated by quasigeostrophic forcing from positive tem- initiated as a result of a cold and dry continental air mass perature or vorticity advection [1] and are associated with a advecting over the relatively warm lake, generating turbulent low-pressure centre tracking zonally following the jet moisture and heat fluxes that destabilize the lower part of the stream. *us, frequent wintertime extratropical storms, such planetary boundary layer (PBL). *e increase of moisture as the Alberta Clipper, Colorado Low, and Nor’easter, track into the lower atmosphere enhances cloud formation and from west to east, affecting surface-atmosphere conditions precipitation along the leeward shores of the Great Lakes within the GLB region. Contrary to these large-scale syn- [1–12]. *e lake-effect vertical atmospheric profile often optic systems are shallow meso-beta scale lake-effect features a moist-neutral or unstable convective boundary snowfall (LES). LES ranges from approximately 5 km to a layer that extends 1 to 4 km above lake surfaces, where a 2 Advances in Meteorology capping stable layer or inversion limits the vertical extent of from Colorado to the lee of Lake Erie and Lake Ontario. convection [12–16]. In addition to LES, lake-enhanced Furthermore, [44] found that the area-averaged snowfall snowfall can occur when synoptic scale systems, driven by across Northern Canada (55°N to 88°N) significantly in- quasigeostrophic forcing, move over the GLB. *e synoptic creased at a rate of 8.8 cm/decade in the late 20th century. system can increase the altitude of the capping inversion, However, in Southern Canada (below 55°N), a negative producing deeper cloud convection, and as a result, increase trend of 0.65 cm/decade during this period was discovered, snowfall. *us, the term lake-induced snowfall is used to with the most decrease occurring in the 1980s [45]. Study describe both lake-effect and lake-enhanced snowfall pro- [17] suggests that while some studies have shown a general cesses, as defined by [17]. Lake-induced snowfall can or- increase in snowfall over the GLB [8, 23, 25, 29, 46, 47], ganize into a spectrum of LES morphologies ranging from recent studies have seen a decline in LES through the later discrete and disorganized cells to organized mesoscale bands half of the 20th century and early 21st century. For example, [16] and include widespread coverage, shoreline bands, [48] showed a decrease in snowfall along the leeward shores midlake bands, and mesoscale vortices [1, 11, 18–20]. of Lake Michigan between 1980 and 2005 and [32] showed a Convective bands are typically long and narrow, between 50 decrease in Central New York between 1971 and 2012. While and 300 km in length and 5 to 20 km in width [1, 10], and can these studies outline trends in North American snowfall, produce highly localized snowfall in cities that are along the there is still a lack in the examination of climatological snowbelts of the GLB. snowfall extremes over the GLB. Little is still known about *e highly populated GLB is home to over 33 million the physical processes influencing the past changes in daily people including 90% of Ontario’s population. Over 1.5 snowfall extremes on the global and hemispheric scales. On a million people reside along the Canadian shores of Lake regional scale, observational studies show large interdecadal Huron and 200,000 along Lake Superior’s [21]. *e Lau- variations in snowfall extreme measures; however, long- rentian Great Lakes support 40% of Canada’s economic term trends remain unclear [49–51]. activities, 25% of its agricultural capacity, and 45% of its *e objective of this study was to assess historical industrial capacity. *ese lakes also support approximately (1980–2015) spatiotemporal trends in snowfall extremes for 400 million dollars in cumulative recreational and com- the Canadian snowbelt zones of Lake Superior and Lake mercial fishing industries and 180 billion dollars in Canada Huron-Georgian Bay (Figure 1). *is will be conducted by and US trade [22]. *us, heavy lake-induced snowfall in the examining snowfall intensity, frequency, and duration and GLB can impact local residents and numerous industries provide potential explanations of the results in the context of [23–27]. *e GLB’s provision on the surrounding com- lake-induced predictor variables, including monthly ex- munities and its climatologically favourable snowfall loca- treme maximum and minimum air temperature, maximum tion gives credence to assessing the historical spatiotemporal wind gust velocity, lake surface temperature (LST), and trends in snowfall extremes within the context of climate annual maximum ice cover concentration. *e study is change. divided into two folds: the first will assess the statistical According to the Intergovernmental Panel on Climate extremes of snowfall intensity, frequency, and duration over Change, Fifth Assessment Report, (IPCC AR5), climate the 36-year period, while the second will examine the trends change, driven by either natural or human forcings can lead in these extremes over the given duration. *e term to changes in the occurrence or strength of extreme weather “snowfall extremes” will be used when referring to all ex- and climate events such as extreme precipitation [28]. tremes in intensity, frequency, and duration, unless other- *erefore, assessing and monitoring spatiotemporal trends wise specified. In this paper, Section 1 presents the in snowfall extremes to a historically changing climate can introduction that provides a background on the develop- provide knowledge as to future behavioural spatiotemporal ment of snowfall within the GLB region; Section 2 outlines trends in snowfall extremes within the densely populated the data and methodology; Section 3 presents the results; Canadian GLB domain and can be useful for sustainability Section 4 provides discussions and analyses on the results; and adaptation studies. and Section 5 summarizes the study and suggests future However, only a few lake-induced snowfall studies fo- potential research avenues. cused on the Canadian GLB while many studies, including [25, 27, 29–32], concentrated on the United States snow- 2. Data and Methods belts. Furthermore, underexaminations of historically ob- served LES extremes compared to LES case studies are 2.1. Datasets. *e datasets used in this study include apparent. *e majority