A climatology of frost extremes across the southeast United States, 1950--1999

This dissertation focuses on growing season characteristics during the spring season across the southeastern United States from 1950--1999. This study focused on three research questions: (1) What is the spatial and temporal variability of last spring frost dates? (2) What are the synoptic conditions associated with frost extremes? and (3) What are the agricultural impacts produced by the extreme frost events at the beginning of the growing season?; Weather stations were included in the study if the average last spring frost date occurred between early February and late March. Ninety-two stations across the study area met these criteria and were used to define the study region. Twenty-five extreme frost events were identified using a frost event criteria based on the timing and geographic extent of the freezing temperatures. Daily minimum temperature data were used to examine the variability and trends in last spring frost dates while gridded surface pressure data were used to produce composite anomaly and mean maps to investigate the atmospheric conditions associated with the extreme frost events.; Considerable year-to-year spatial variability exists in the timing of last spring frost dates across the southeastern United States with the highest variability occurring in the southern portion of the study area. A clear trend towards earlier last spring frost dates has been established at many locations since the late 1980s.; Several common surface features were associated with the extreme frost events including strengthened North Pacific and North Atlantic subtropical high pressure systems and strong cold-core low pressure systems in the Bering Sea and northern Atlantic. Temperatures were highly variables in advance of the extreme frost events.; A content analysis and a historical assessment of agricultural impacts from the extreme frosts were completed using six newspaper sources. Two-thirds of the frost events produced light to moderate damage with the remaining frost events producing either considerable damage or no damage at all. The increased use of preventative measures and the decreasing acreage of farmland have reduced the agricultural losses of frost events in recent times across the Southeast United States.