A Climatology of Southern Appalachian Cold-Air Damming

Abstract

30-yr climatology (1981?2010) of cold-air damming (CAD) events in the southern Appalachians was conducted using hourly surface observations and North American Regional Reanalysis (NARR) data. Analysis of the spatial distribution and frequency of these events reveals that some part of the Southeast is affected by CAD on 50 days out of each year, and even the northern Florida panhandle and much of Alabama experience CAD conditions on about 30 days annually. Spatially, different CAD types tend to exhibit one of two patterns in the southernmost extent of the cold-air dome: a more southerly dome with a ridge axis oriented from north-northeast to south-southwest or a more westerly dome with a ridge axis in a northeast to west-southwest orientation. These patterns may be the result of both splitting around the region of higher terrain in east-central Alabama and Coriolis forcing in stronger CAD types with higher wind speeds. Analysis of the frequency of CAD by type on a month-by-month and year-by-year basis confirms previous work that CAD is much more frequent during the cold season versus the warm season, with CAD occurring on 6.8 days month?1 during December and only 1.3 days month?1 during July. Analysis was also stratified by CAD type, revealing that weak/dry events were the most common. Classical type events with stronger and more favorably positioned parent highs exhibited the longest average duration, nearly 45 h, while other CAD types averaged approximately half as long.