Introduction to Human-Environment Geography: A Laboratory Manual

A laboratory manual designed for use in introductory college courses as an Open Educational Resource. Each of the ten laboratory experiments are presented as stand-alone chapters within this book to increase accessibility and potential adoptability by instructors seeking only some of the provided content.https://digitalcommons.unomaha.edu/geoggeolfacbooks/1004/thumbnail.jp

Discharge responses associated with rapid snow cover ablation events in the Susquehanna and Wabash River basins

In the mid-latitudes, snow plays a critical role in regional hydroclimate, with snow ablation variability in ephemeral regions representing an area of essential research. Due to a lack of historical snow-water-equivalent data in the eastern United States, recent research has substituted daily snow depth changes for ablation. These studies, however, do not explicitly examine if such a substitution yields a snowmelt hydrological signal, an important component of water resource management. As such, this study evaluates if ablation events, as defined as a daily snow depth decrease, subsequently result in increased river discharge within two similarly sized watersheds in the eastern United States: the Wabash and Susquehanna River basins. For both basins, \u3e75% of snow ablation events resulted in a positive river discharge response (increase in discharge) at a 3-day lag. Furthermore, results show a significant and positive relationship between ablation event frequency and seasonal discharge response, such that an increase (decrease) in seasonal snow ablation event frequency yields an increase (decrease) in associated seasonal river discharge at a 3-day lag. These relationships indicate that inter-diurnal decreases in snow depth do carry hydrological implications, adding confidence that such a definition of ablation is appropriate for climatological applications

Atmospheric drivers of snowfall and snow cover ablation variability within the Great Lakes Basin of North America

Leathers, Daniel J.This dissertation examines the relationships between snow and synoptic-scale atmospheric circulation in the Great Lakes region of North America in a series of three journal articles. The first assesses the variability and long-term trends of lake-effect snowfall along the eastern shores of Lakes Erie and Ontario, and determines the particular synoptic-scale weather types that drive the variability in snowfall. These weather type frequencies explain over 68% of inter-annual lake-effect snowfall variability, and between 89-95% of the observed linear changes in snowfall can be explained by long-term changes in the frequency and snowfall rates of these synoptic patterns. ☐ The second article builds a climatology of snow ablation events within the Great Lakes basin by isolating ablation from a daily gridded snow depth product. Ablation events are latitudinally-dependent, with peak probability of an event shifting northwards during the spring months in conjunction with enhanced incoming solar radiation, surface air temperatures, and atmospheric moisture. No long-term changes in the seasonal timing of ablation events are detected within the basin, however two spatially coherent regions corresponding to the northern Lake Superior and the eastern Lake Huron/Georgian Bay drainage basins did experience significant decreases and increases in inter-annual ablation event frequency from 1960-2009, respectively. Such changes are hypothesized to be driven by changes in the frequency of particular mid-latitude cyclones influencing the region and long-term trends in lake-effect snowfall. ☐ The third article employs a synoptic-classification procedure that identifies and analyzes the atmospheric conditions that lead to snow ablation events across the Great Lakes basin. Three primary categories of synoptic weather types lead to ablation, corresponding to ‘southerly flow’, ‘rain-on-snow’, and ‘high-pressure overhead’ patterns. Each pattern influences the meteorological conditions forcing ablation at the surface, and exhibits substantial inter-annual variability. The second and third most common ablation-inducing synoptic weather type categorizes, ‘high-pressure overhead’ and ‘rain-on-snow’, are respectively increasing and decreasing in inter-annual frequency from 1960-2009. Together, these three articles showcase the variable forcings of snow in the Great Lakes basin, and highlight the importance of understanding the links between atmospheric circulation and cryospheric water resources.University of Delaware, Department of GeographyPh.D

Lake-induced snowfall associated with lakes Erie and Ontario in CMIP5 GCMs

Leathers, Daniel J.In this study, an analysis of simulated lake-induced snowfall from 2006-2100 is conducted, investigating the presence of a lake-induced snowfall signal to the lee of Lakes Erie and Ontario. Output from seven fully coupled global climate models (GCM) s are used from phase five of the Coupled Model Intercomparison Project (CMIP5). Snowfall trends over the entire study area and in the defined lake-induced Snowbelt are examined seasonally for two Representative Concentration Pathway (RCP) scenarios. In addition, physical mechanisms associated with these trends, such as lake lapse rates, surface temperatures and snow to total precipitation ratios are examined. The models perform well when compared to derived and observed snowfall observations despite model difficulties in resolving small scale orographic and finite lake effect processes. Snowfall declines by 20 - 45% over the entire region, with snowfall actually increasing in the lake-induced region during the first quarter century before declining rapidly in RCP 8.5. An additional 1.7 cm snow-water-equivalent (SWE) signal of purely lake-induced snowfall is detected within the ensemble mean of the defined lake-induced Snowbelt to the lee of the two lakes that is not seen in the grid cells outside of the lake belt. Surface two-meter temperature is found to have the most significant impact on snowfall changes in the region, with impacts not on total precipitation, but on the percentage of precipitation falling as snow. Lake lapse rates were found to not provide enough evidence to draw useful conclusions on snowfall trends.University of Delaware, Department of GeographyM.S