Browsing by Author "Henderson, Gina R."
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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 European snowcover extent variability: a climatology from 1967-2002(University of Delaware, 2006) Henderson, Gina R.Snowcover in Europe represents an important component of the region’s climatic system. Variability in its extent can have major implications on factors such as low-level temperatures, the amount of heat released from soil to the overlying atmosphere and energy allocation involved in the warming and melting of the snow pack. The majority of studies investigating Northern Hemisphere snowcover identify European snowcover extent as a subset of the Eurasian record, possibly masking complexities of this subset. This study explores the variability of European snowcover extent from 1967-2000, with the region in question including that area of Europe extending eastward to the Ural Mountains (60°E). Using the 89x89 gridded NOAA Northern Hemisphere weekly snowcover product, area estimates of seasonal snowcover were calculated, and their relationship to gridded temperature, precipitation and sea level pressure data analyzed. The spatial variability of snowcover extent was also explored using GIS mapping techniques. The influence of 500-hPa geopotential heights, sea-surface temperature and sea-level pressure variability on snowcover area was also investigated. Results indicate strong associations between snowcover extent and these variables, with a distinctive north/south di-pole pattern evident in the sea-level pressure.