Climate trends and synoptic patterns associated with major precipitation events of the southern Appalachians.

摘要

This study focuses on the southern Appalachians, a region of pronounced biodiversity. While environmental change in the area is documented, our understanding of associated regional climate change remains less certain. For this reason, surface observations of minimum, maximum, and mean temperature, total precipitation, and total snowfall from 463 stations within the region were obtained from the National Climatic Data Center's Cooperative Observer Program to facilitate the construction of a baseline climatology focused on temporal trends and spatial clusters.;First-order temporal trends show that the southern Appalachian region experienced statistically significant cooling trends during 1931-2006, although two-phase regression results also reveal that statistically significant warming trends emerged during recent decades. This warming was most evident in wintertime and minimum temperatures with January temperatures warming as much as 4.00°C between the mid 1970s and 2006. Overall, diurnal and annual temperature ranges decreased, while annual precipitation increased over the study period. Snowfall totals decreased at low and mid elevations and a statistically significant increase occurred at high elevations. The recent warming and decreasing temperature ranges for this locale support trends presented within recent reports from Intergovernmental Panel on Climate Change and the United States Global Change Research Program. The effectiveness of the cluster analysis was limited by the availability and spatial resolution of the observation stations. However, the resulting clusters still depicted relationships between stations of similar geographic locations and elevations and up to five climate regimes were defined for the region.;Additionally, a study of synoptic patterns during 1437 major precipitation events spanning 1979-2006 revealed up to 11 common synoptic patterns. The synoptic patterns were created by objective, subjective, and hybrid clustering approaches. The results from the objective approach differed from the subjective approach, and patterns uncovered by the hybrid approach had similarities to both the objective and subjective approaches. Since results varied depending on the cluster approach used, it is recommended that future studies should not rely solely on one approach when clustering synoptic patterns.;A temporal analysis showed that some synoptic patterns became more or less frequent over the 1979-2006 period and some trends were statistically significant. Precipitation events associated with low-pressure and frontal systems became more frequent, whereas precipitation events associated primarily with orographic lifting or thermodynamics became less common. The results from this dissertation build upon those from previous studies and provide a more complete summary of the region's recent climate, one that should help inform future climate studies of the region and inform those who manage the region's ecosystems.