Browsing by Author "Suriano, Zachary J."
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Item Atmospheric Drivers Associated with Extreme Snow Ablation and Discharge Events in the Susquehanna River Basin: A Climatology(Journal of Applied Meteorology and Climatology, 2023-11-02) Suriano, Zachary J.; Henderson, Gina R.; Arthur, Julia; Harper, Kricket; Leathers, Daniel J.Extreme snow ablation can greatly impact regional hydrology, affecting streamflow, soil moisture, and groundwater supplies. Relatively little is known about the climatology of extreme ablation events in the eastern United States, and the causal atmospheric forcing mechanisms behind such events. Studying the Susquehanna River basin over a 50-yr period, here we evaluate the variability of extreme ablation and river discharge events in conjunction with a synoptic classification and global-scale teleconnection pattern analysis. Results indicate that an average of 4.2 extreme ablation events occurred within the basin per year, where some 88% of those events resulted in an increase in river discharge when evaluated at a 3-day lag. Both extreme ablation and extreme discharge events occurred most frequently during instances of southerly synoptic-scale flow, accounting for 35.7% and 35.8% of events, respectively. However, extreme ablation was also regularly observed during high pressure overhead and rain-on-snow synoptic weather types. The largest magnitude of snow ablation per extreme event occurred during occasions of rain-on-snow, where a basinwide, areal-weighted 5.7 cm of snow depth was lost, approximately 23% larger than the average extreme event. Interannually, southerly flow synoptic weather types were more frequent during winter seasons when the Arctic and North Atlantic Oscillations were positively phased. Approximately 30% of the variance in rain-on-snow weather type frequency was explained by the Pacific–North American pattern. Evaluating the pathway of physical forcing mechanisms from regional events up through global patterns allows for improved understanding of the processes resulting in extreme ablation and discharge across the Susquehanna basin. Significance Statement The purpose of this study is to better understand how certain weather patterns are related to extreme snowmelt and streamflow events and what causes those weather patterns to vary with time. This is valuable information for informing hazard preparation and resource management within the basin. We found that weather patterns with southerly winds were the most frequent patterns responsible for extreme melt and streamflow, and those patterns occurred more often when the Arctic and North Atlantic Oscillations were in their “positive” configuration. Future work should consider the potential for these patterns, and related impacts, to change over time.Item Atmospheric drivers of snowfall and snow cover ablation variability within the Great Lakes Basin of North America(University of Delaware, 2018) Suriano, Zachary 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.Item Lake-induced snowfall associated with lakes Erie and Ontario in CMIP5 GCMs(University of Delaware, 2014) Suriano, Zachary 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.