Long-Term Sahelian Drought from the Late 1960's to the Mid-1980's and its Relation to the Atmospheric Circulation

[摘要] The African atmospheric circulation as related to the long-term Sahelian drought from the late 1960's to the mid-1980's is investigated.Quantitative analysis of the tropical African rainbelt for August shows that the reduction in total rainfall is more responsible for the decreasing trend in the Sahelian rainfall over the period than the equatorward retraction of the rainbelt.This trend of the rainbelt is accompanied by increasing trends in both 700 mb heights and temperatures throughout the tropical zone for August. These trends are most pronounced over the Sahelian zone where the average trend values during the period 1959-1984 are 14.7 gpm/decade and 0.62°C/decade for geopotential and temperature, respectively. The concurrent increases in the 700 mb heights and temperatures are likely caused by the intensification of subsidence, primarily south of the Northern Hemisphere subtropical high, without a substantial displacement of its axis.

[学科分类] 大气科学