Satellite Perspectives on the Spatial Extent of New Snowfall in the Southern Appalachian Mountains

Sugg, Johnathan

The southern Appalachian Mountains (SAM) are a heavily forested mid-latitude mountain region and provide an ideal location for assessing the suitability of satellite-derived snow maps and explicitly linking atmospheric circulation to the spatial patterns of new snowfall. Although a variety of synoptic-scale circulation regimes contribute to mean annual snowfall (ranging from roughly 25 cm in the lowest valleys to over 250 cm at the highest elevations), atmospheric processes have largely been absent from previous efforts to quantify the spatial patterns of new snowfall. In this thesis, the suitability of fractional snow cover (FSC) maps from the Moderate Resolution Imaging Spectroradiometer (MODIS) is examined and the spatial extent of snowfall is determined according to synoptic-scale circulation. Version 5 FSC and true color snow maps are analyzed after 122 snow events (e.g., Miller A/B cyclones, southeastward tracking clippers, and NW Flow snowfall) from October 2006 to April 2012 to provide a suitability analysis of MODIS products for use in the SAM. MODIS data are evaluated based on their suitability by snow year, climatological season, synoptic-scale circulation, and between heavy and light snowfall events. For each event, FSC distribution and total snow covered area are calculated and then compared with available in-situ observations from Poga Mt., North Carolina and from National Weather Service cooperative observer stations. Case studies are presented to discuss linkages of synoptic-scale circulation with resulting snow cover patterns in the context of other meteorological products. Results indicate the SAM presents unique meteorological, physical, and spectral characteristics that are ideal to evaluate the suitability of MODIS for measuring snow cover. Out of 122 observed snow events, 63 are considered suitable for analysis with the FSC maps. MODIS successfully mapped 89% of the heaviest snowfall events and less than 50% of the lighter events. The highest FSC values are observed after Miller A/B cyclones, southeastward tracking clippers, and on windward slopes following Northwest Flow snowfall events. These findings indicate that MODIS data can be successfully used to link broader atmospheric circulation processes of snowfall with the spatial patterns of snow cover. The methods employed in this thesis are readily transferrable to other mid-latitude mountain regions with dense forest cover. In particular, these results will be useful for future studies seeking to incorporate remotely sensed data for understanding synoptic perspectives between individual events. The findings presented here are important for contributing to knowledge of future climate changes to snow cover in the SAM and in other mid-latitude mountain regions.