夏季东亚季风与西太平洋副高对福建旱涝影响的诊断分析

利用NCEP/NCAR发布的850 hPa风场和OLR场以及福建38个站月降水资料, 分析了福建夏季旱涝与东亚夏季风及西太平洋副高的关系。结果表明夏季旱涝与夏季风强弱及副高南北位置密切相关。涝 (旱) 年在东亚季风系统中的热带季风环流出现异常加强 (减弱), 副热带季风环流则出现异常减弱 (加强); 涝年副高平均脊线位置偏北于27°N附近, 旱年则偏南于24°N附近; 由春入夏, 再由夏入秋副高南北位置的季节位移, 涝年先是急速北跳, 而后又急速南撤, 旱年却进退平缓。旱涝年东亚中高纬度环流亦表现出不同特征, 涝 (旱) 年一般没有 (有) 出现阻塞形势, 中纬度纬 (经) 向环流发展, 副热带锋区北抬 (南压), 研究还进一步揭示了夏季副高位置南北偏离影响夏季各月降水及其分布的不同形式。

Impact of East Asian Summer Monsoon and Subtropical Anticyclone over Western Pacific on Droughts/Floods in Fujian

Based on 850 hPa NCEP/NACR wind and OLR data, different features of East Asian summer monsoon and the subtropical anticyclone over western Pacific between dry and wet years in Fujian Province are discussed. The main results are as follows: In the East Asian summer monsoon system, the intensity of tropical monsoon circulation strengthens (weakens) while the intensity of subtropical monsoon circulation weakens (strengthens), with a northward (southward)-slanted average location of the western Pacific high in wet (dry) years. During the seasonal transition from spring to summer and summer to autumn, the seasonal northward and southward jumps of the high ridge in wet years are quicker, inversely the jumps in dry years are slower. The "-+-" ("+-+") anomaly pattern dominates over East Asia at 500 hPa in wet (dry) years, i. e., there is not (is) blocking situation while the subtropical frontal zone moves northward (southward) in wet (dry) years. Results also show different features of the impacts of northward-and southward-slanted subtropical high locations on rainfall and their distributions in various months in summer in Fujian Province.