A Climatological Study of Extreme Cold Surges along the African Highlands

作者：Crossett Caitlin C; Metz Nicholas D^*

来源：Journal of Applied Meteorology and Climatology, 2017, 56(6): 1731-1738.

DOI：10.1175/JAMC-D-15-0191.1

Equatorward-moving cold surges occur along the lee of high terrain during the cold season. Even though the east coast of Africa features high terrain, little research exists on cold surges along the African highlands despite the fact that these surges could have potentially large agricultural and societal effects. This paper examines a 5-yr climatology of the most extreme African-highlands cold surges spanning the 2008-12 period. During these years, 186 cold surges occurred to the lee of the African highlands, with 84 events extending between 30 degrees and 35 degrees S (type 1), 27 extending between 25 degrees and 30 degrees S (type 2), and 75 extending equatorward of 25 degrees S (type 3) based on the 1000-850-hPa thickness pattern. This climatology reveals that extreme Africanhighlands cold surges have a climatological maximum in September. Cold surges of type 1 and type 2 tend to occur throughout the Southern Hemisphere winter and spring, whereas surges of type 3 are generally confined to the winter months. These cold surges can last from 2 to 8 days, with the highest frequency of events spanning a 3-day period. A typical cold-surge event features maximum 925-hPa meridional flow of 30.0-39.9 kt (1 kt = 0.51 m s(-1)) that most frequently advects cold Antarctic air to between 15.0 degrees and 24.9 degrees S and at times as far as the equator.

• 出版日期2017-6