Demarcating the worldwide monsoon
Demarcating the worldwide monsoon
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DOI：
10.1007/s704-002-8204-0
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发表时间：
2002
影响因子：
3.4
通讯作者：
Weihong Qian;Yi Deng;Y. Zhu;W. Dong
中科院分区：
文献类型：
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作者：
Weihong Qian;Yi Deng;Y. Zhu;W. Dong
季风是一种全球性的气候现象。本文讨论了全球季风区大气环流的季节性逆转和干湿交替。利用1950-1999年NCEP/NCAR 850 hPa风场再分析资料和1980-1995年NOAA极轨卫星观测的对流层上层水汽亮温资料。在热带地区，有三个大型湿UTWV中心。副热带夏季风可以定义为这些中心的扩张和越赤道气流的影响。具体地说，干/湿时段转变由小于244 K的BT值确定。对南亚和北非季风区、亚洲-西北太平洋季风区、澳大利亚-西南太平洋季风区以及北美和南美季风区的干湿转换和流场特征进行了研究，结果表明，许多副热带地区的夏季风可以由越赤道气流和干湿转换两种形式来定义。在中低纬度地区，有6个主要的干湿过渡区，其干湿期持续时间超过1个月。变化最显著的区域位于亚热带北非-亚洲-西北太平洋上空。其他的则出现在亚热带的南非、澳大利亚、西南太平洋、墨西哥-加勒比海和亚热带的南美洲。此外，有三个区域只满足两个指标（越赤道气流和干/湿过渡）中的一个。第一个是赤道附近，跨赤道气流的方向交替，但从未经历过干/湿的过渡。第二个是在北非，只有干/湿的过渡可以找到，但没有越赤道气流。第三个是在中国北方、南非和北美北方的中纬度地区。这些区域受到越赤道气流的影响，但对流层上层的水蒸气含量没有热带区域那么高。
The monsoon is a global climate phenomenon. This paper addresses the seasonal reversal of atmospheric circulation and the transition of dry/wet spells in the monsoon regions worldwide. The NCEP/NCAR 850 hPa wind reanalysis data for 1950–1999 and the upper-tropospheric water vapour (UTWV) band brightness temperature (BT) data observed by NOAA polar orbiting satellites for 1980–1995 are used. In the tropics, there are three large wet-UTWV centres. The summer monsoon in the subtropics can be defined as the expansion of these centres associated with the influence of cross-equatorial flows. Specifically, the dry/wet spell transition is determined by the BT values that are smaller than 244 K. The regions of the South and North African monsoons, the Asian-northwest Pacific and Australian-Southwest Pacific monsoons, and the North and South American monsoons are examined with a focus on the dry/wet spell transition and stream field features.Findings suggest that the summer monsoons over many subtropical regions can be defined by both cross-equatorial flows and dry/wet spell transitions. In the mid- and low-latitudes, there exist six major dry/wet spell transition regions with a dry or wet period lasting more than one month. The region of most significant change is located over the subtropical North Africa–Asia–northwest Pacific. The others appear over subtropical South Africa, Indonesia–Australia, southwest Pacific, the Mexico-Caribbean Sea, and subtropical South America. In addition, three regions exist where only one of the two indicators (cross-equatorial flow and dry/wet transition) is satisfied. The first is near the Equator where the directions of cross-equatorial flows alternate but a dry/wet spell transition is never experienced. The second is over North Africa where only the dry/wet spell transition can be found but not the cross-equatorial flows. The third is over the mid-latitude regions in North China, South Africa, and northern North America. These regions are influenced by cross-equatorial flows but the upper-tropospheric water vapour content is not as high as that in tropical regions.