Decadal-Scale Trends in Transition Weather Types and Atmospheric Circulation

The application of synoptic-scale weather classification systems to studies of the impact of climate change continues to emerge as a method to investigate regional and global alterations to the Earth‟s atmosphere. The Spatial Synoptic Classification (SSC, Sheridan 2002) is a semi-automated air mass/weather-type identification system that has been applied in a variety of climatic and biometeorological investigations. The system, originally developed by Kalkstein et al. (1996) and later improved by Sheridan (2002), categorizes daily weather into one of seven discrete types: six air masses and one transition category, the latter of which attempts to identify days with a distinct change from one weather type to another. The SSC remains operational, and categorizes daily weather for hundreds of stations across North America and Europe. For many stations, the record dates from 1949 through 2007. This work will investigate two major questions related to changes in the synoptic-scale climate of the United States through study of the
SSC‟s transition category.