How Much Do Tropical Cyclones Affect Seasonal and Interannual Rainfall Variability over the Western North Pacific?
How Much Do Tropical Cyclones Affect Seasonal and Interannual Rainfall Variability over the Western North Pacific?
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DOI：
10.1175/2009jcli2646.1
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发表时间：
2009-10-15
影响因子：
4.9
通讯作者：
Wang, Bin
中科院分区：
文献类型：
--
作者：
Kubota, Hisayuki;Wang, Bin
作者利用22个站点的降雨资料，研究了热带气旋（tc）对北太平洋西部（WNP）季节和年际降水变化的影响。当一个TC位于距该站影响半径（1000公里）以内时，利用该站资料估计每个站点TC引起的降雨量。TC降雨比例的时空变化主要沿着东西向靠近北纬10度（78 - 13度）的岛链和东经125度（120 - 130度）附近的南北向岛链进行。沿10°N，总降雨量的季节性主要由受WNP季风槽影响的非tc降水决定。TC雨的比例相对较低。在7 - 12月的高温季节，关岛的高温降雨量占总降雨量的30%，科罗尔和雅浦的高温降雨量占总降雨量的15%-23%，其他站的高温降雨量不足10%。而在副热带高压所在的125°E沿线，7 - 10月的TC高峰期，TC降雨量占18°- 26°N地区总降雨量的50%-60%。在台湾花莲，TC降雨量超过总降雨量的60%。厄尔尼诺-南方涛动（ENSO）对TC雨量和总雨量的年际变化具有重要的调节作用。沿10°N，在厄尔尼诺发展期和成熟期（3月至次年1月），TC降雨量与总降雨量之比高于气候学，而在厄尔尼诺衰减期，TC降雨量与总降雨量之比低于气候学。拉尼娜的情况正好相反，只是它的影响持续时间较短。此外，在厄尔尼诺发展年夏季，季节总降雨量的增加主要是由于TC降雨量的增加。在随后的秋季，菲律宾海上空出现反气旋异常，TC降水向东转移；因此，菲律宾和台湾的总降雨量减少。东经140度以东的总降水量变化不大，主要是由于TC西进增强了TC降水，抵消了非TC降水的减少。在120°~ 130°E的经向岛链上，从秋季开始至次年春季，总降水异常受ENSO的影响，仅在ENSO年的秋季（8 - 11月），TC降水的变化主导了总降水的变化。研究结果表明，在热带西北地区和副热带东亚季风区（东经120度以东），降水的季节和年际变化受局外环流变化的控制。这些季风域外的变化可能通过改变TC的成因和路径而实质性地影响夏季季风降雨。
The authors investigate the effects of tropical cyclones (TCs) on seasonal and interannual rainfall variability over the western North Pacific (WNP) by using rainfall data at 22 stations. The TC-induced rainfall at each station is estimated by using station data when a TC is located within the influential radius (1000 km) from the station. The spatial-temporal variability of the proportion of TC rainfall is examined primarily along the east west island chain near 10 degrees N(between 78 and 13 degrees N) and the north-south island chain near 125 degrees E (between 120 degrees and 130 degrees E).Along 10 degrees N the seasonality of total rainfall is mainly determined by non-TC rainfall that is influenced by the WNP monsoon trough. The proportion of the TC rain is relatively low. During the high TC season from July to December, TC rainfall accounts for 30% of the total rainfall in Guam, 15%-23% in Koror and Yap, and less than 10% at other stations. In contrast, along 125 degrees E where the WNP subtropical high is located, the TC rainfall accounts for 50%-60% of the total rainfall between 18 degrees and 26 degrees N during the peak TC season from July to October. In Hualien of Taiwan, TC rainfall exceeds 60% of the total rainfall.The interannual variability of the TC rainfall and total rainfall is primarily modulated by El Nino-Southern Oscillation (ENSO). Along 10 degrees N, the ratio of TC rainfall versus total rainfall is higher than the climatology during developing and mature phases of El Nino (from March to the following January), whereas the ratio is below the climatology during the decaying phase of El Nino. The opposite is true for La Nina, except that the impact of La Nina is shorter in duration. Furthermore, in summer of El Nino developing years, the total seasonal rainfall increases primarily because of the increase of TC rainfall. In the ensuing autumn, an anticyclonic anomaly develops over the Philippine Sea and TC rainfall shifts eastward; as a result, the total rainfall over the Philippines and Taiwan decreases. The total rainfall to the east of 140 degrees E, however, changes little, because the westward passage of TCs enhances TC rainfall, which offsets the decrease of non-TC rainfall. Along the meridional island chain between 120 degrees and 130 degrees E, the total rainfall anomaly is affected by ENSO starting from the autumn to the following spring, and the variation in TC rainfall dominates the total rainfall variation only in autumn (August-November) of ENSO years.The results from this study suggest that in the tropical WNP and subtropical East Asian monsoon regions (east of 120 degrees E), the seasonal and interannual variations of rainfall are controlled by changes in nonlocal circulations. These changes outside the monsoon domain may substantially affect summer monsoon rainfall by changing TC genesis and tracks.