Interannual Variation of Seasonal Changes of Precipitation and Moisture Transport in the Western North Pacific
Interannual Variation of Seasonal Changes of Precipitation and Moisture Transport in the Western North Pacific
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DOI：
10.2151/jmsj.83.107
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发表时间：
2005-02
影响因子：
3.1
通讯作者：
Miki Hattori;K. Tsuboki;T. Takeda
中科院分区：
文献类型：
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作者：
Miki Hattori;K. Tsuboki;T. Takeda
利用全球逐月降水资料和NCEP-NCAR(国家环境预报中心-国家大气研究中心)再分析资料，研究了1979~1998年20年来西北太平洋6~8月降水和水汽输送的年际变化。根据菲律宾东部6、8月份强降水区和降水量的经向移位，将降水量的季节变化分为A型和B型，A型以6~8月强降水区北移、降水量增加为特征。A类又分为两类：A1亚类和A2亚类。前者表现为降水逐渐增多，强降水区域由6�NT o 16�N向北移动；后者以6�NT o 16�N为特征，6月降水较强，7月降水减少，8月降水明显增多，最大值出现在8月；B类降水由13�NT o 22�N向北转移，表现为季节性变化，6~8月降水基本无增加，也无明显北移。A型和B型降水量的差异对应于来自印度洋的西风水汽通量和低层穿越赤道的南风水汽通量。结果表明，B型的西风和南风水汽通量远小于A型，尤其是在8月份。A2亚型的西风水汽通量大于A1亚型。西风水汽通量的季节变化表现为A1亚型逐渐增加，A2亚型6、8月显著增加，7月减少。它们分别对应于降水量。8月A型西风水汽通量大和菲律宾以东强水汽辐合与欧亚大陆低槽向东延伸有关。强降水区的北移对应于向东延伸的槽的加强。
Interannual variation of seasonal changes of precipitation and moisture transport in the western North Pacific from June to August is studied using global monthly precipitation data, and NCEP-NCAR (National Center for Environmental Prediction-National Center for Atmospheric Research) reanalysis for 20 years from 1979 to 1998. According to the meridional shift of the intense precipitation area and precipitation amounts in June and August to the east of the Philippines, the seasonal changes of precipitation are categorized into Types A and B. Type A is characterized by the northward shift of intense precipitation area and the increase of precipitation from June to August. Type A is further classified into two: Sub-Types A1 and A2. The former is characterized by the gradual increase of precipitation and the northward shift of the intense precipitation area from 6 � Nt o 16 � N. The latter is characterized by a relatively intense precipitation in June, decrease of precipitation in July, significant increase of precipitation with a maximum in August, and the northward shift from 13 � Nt o 22 � N. Type B is characterized by a seasonal change, with almost no precipitation increase nor northward shift from June to August. Difference in the precipitation amount between Types A and B corresponds to the westerly moisture flux originating from the Indian Ocean, and the southerly moisture flux which comes across the equator at the lower level. It is found that the westerly and southerly moisture flux in Type B are much smaller than those in Type A, especially in August. The westerly moisture flux in Sub-Type A2 is larger than that in Sub-Type A1. The seasonal changes of westerly moisture flux show gradual increase in Sub-Type A1, and significant increase in June and August and decrease in July in Sub-Type A2. They are corresponding to those of the precipitation amount, respectively. The large westerly moisture flux and the strong moisture convergence to the east of the Philippines in August in Type A, are associated with the eastward extension of the trough from the Eurasian continent. The northward shift of the intense precipitation area corresponds to the intensification of the eastward extended trough.