北非高压的气候特征及其对中国夏季降水的影响

The Climatic Character of North Africa Subtropical High and Its Effect on Summer Precipitation in China

以北非高压的 5个指数为基础 ,分析了北非高压的气候特征 :北非高压强度越强 ,范围越广 ,东伸越明显且脊线偏南 ,反之偏西偏北 ;北非高压的强弱趋势、南北位置和东西位置具有显著的季节变化 ,其中 5月下旬和 6月下旬有两次明显的跳跃 ,在时间上比西太平洋副高两次北跳提前 2～ 3候。北非高压对中国夏季降水影响主要表现为我国东部地区以长江为界的南北降水具有反相分布特点 ,西藏高原上东、西部降水存在相反分布。最后 ,讨论了北非高压与西太平洋副高及东亚环流的关系 ,发现 :两个高压的强度、范围和南北及东西位置的变化趋势基本一致 ,从西亚到太平洋呈现正、负、正的波列分布特征。这种特征组成了亚洲地区纬向型的遥相关分布 ,这可能是造成中国夏季降水时空分布的原因之一。

Based on five indices,the climatic character of North Africa subtropical high is analyzed.The analysis results show that the stronger the North Africa subtropical high,the wider its range;the farther the eastward extension of the high,the lower the latitude of its ridge line.The North Africa subtropical high shows distinct seasonal changes in its intensity and location,with two obvious northward jumps in late May and late June,about two to three pentads earlier than the West Pacific subtropical high.The influence of North Africa subtropical high on the summer precipitation of China is reflected in the out of phase distribution of precipitation in the south and north parts of eastern China,and in the east and west parts of the Tibetan Plateau.At last,the relationship of North Africa subtropical high with the West Pacific subtropical high and the East Asian atmospheric circulation is discussed,and it is found that the variation trends in intensity,range and location of the two highs are basically identical,displaying a distributive character of positive negative positive wavetrain over western Asian to the eastern Pacific ocean.This zonal teleconnection of wavetrain form over the Asian region might be one of causes for the temporal/spatial inhomogeneity of summer precipitation over China.