Continental-scale snow cover anomalies and air mass frequencies and characteristics across eastern North America

The large-scale distribution of snow cover and its effects on the global climate system is a topic of interest to those involved in climate diagnostics and climate modeling. Continental scale snow cover extent has been monitored from space for more than three decades in visible wavelengths. This imagery can be utilized to identify months of anomalously large and small snow cover extents across the North American continent. Because the radiation and moisture balances at the earth's surface are greatly affected by the presence or the absence of a snow cover, air mass characteristics are dependent upon extremes in snow cover extent. Air mass calendars have been produced for over 200 stations across the United States and Canada using the Spatial Synoptic Classification system developed at the University of Delaware. These calendars are generally available for each day during the period 1948 through 1998. In this research, visible snow cover extent data is used in conjunction with air mass calendars to investigate the influence of snow cover extent on air mass frequency and character across North America, east of the Rocky Mountains. Results indicate that extremes in North American snow cover extent are strongly associated with air mass frequency and character anomalies throughout the eastern portion of the continent. The frequency of some air mass types change by as many as 15 days per month during periods of anomalous continental-scale snow cover extent. These large variations in the air mass climatology of eastern North America have important impacts on many segments of society including economic interests, agriculture and transportation.