| ENSO对中国冬半年降水影响的不对称性及机制分析 |
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| 引用本文： | 李天然,张人禾,温敏.ENSO对中国冬半年降水影响的不对称性及机制分析[J].热带气象学报,2017,33(1):1-10. |
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| 作者姓名： | 李天然 张人禾 温敏 |
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| 作者单位： | 1.中国气象科学研究院，北京 100081 |
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| 基金项目： | 国家自然科学基金项目41221064公益性行业 (气象) 科研专项经费项目GYHY201306004 |
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| 摘 要： | 利用1979—2010年观测和再分析资料，诊断分析ENSO对中国华南冬半年降水的影响及其机制。结果表明，在El Ni?o冬半年期间，东亚沿岸上空对流层低层南风的增强导致了水汽输送明显偏多，水汽在华南辐合，使得大气可降水量和比湿增加，降水显著偏多。而在La Ni?a冬半年期间，这些大气要素并没有呈现显著的相反变化，负异常的量值很弱并在统计上不显著。通过进一步分析El Ni?o和La Ni?a冬半年期间季节内振荡的特点，给出一种华南冬半年降水对ENSO信号不对称响应的物理解释。El Ni?o期间，热带西太平洋到南海地区的季节内振荡不活跃，与El Ni?o相联系的西北太平洋反气旋性环流异常造成的水汽输送以及水汽辐合在华南能够稳定维持，致使华南降水明显偏多。但在La Ni?a冬半年期间，季节内振荡很活跃，与La Ni?a相联系的西北太平洋气旋性环流异常受到季节内时间尺度的扰动影响，ENSO的年际变化信号被季节内振荡破坏，使得西北太平洋和华南的年际异常信号不能得到稳定维持，导致与ENSO信号相联系的年际变化在统计上不显著。因此，热带西太平洋到南海地区的季节内振荡强度在El Ni?o和La Ni?a冬半年期间的差异，是华南冬半年降水对ENSO信号不对称响应的一个主要原因。
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| 关 键 词： | 气候学 中国降水特征 ENSO 季节内振荡 冬半年 |
| 收稿时间： | 2015-08-26 |
IMPACT OF ENSO ON THE PRECIPITATION OVER CHINA IN WINTER HALF YEAR |
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| Institution: | 1.Chinese Academy of Meteorological Sciences, Beijing 100081, China2.University of Chinese Academy of Sciences, Beijing 100049, China3.Guangzhou Central Weather Observatory, Guangzhou 510640, China |
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| Abstract: | The impact of ENSO on the precipitation over China in winter half year is investigated by using observed and reanalysis datasets in 1979—2010. The results show that positive precipitation anomalies with statistical significance appear over southern China in El Ni?o episodes, which are caused by the enhanced warm and humid southwesterliesalong the East Asian coast in the lower troposphere. The enhanced southwesterlies transport more water vapor to southern China, and the convergence of water vapor over southern China increases the precipitable water and specific humidity in the atmosphere. In La Ni?a episodes, no reverse precipitation anomalies with statistical significance appear over southern China. Although atmospheric elements are changed reversely, they are not statistically significant as those in El Ni?o periods. The possible physical mechanism of the asymmetric impact of ENSO cycles on the precipitation over southern China is investigated by analyzing the intraseasonal oscillations (ISOs) in El Ni?o and La Ni?a, respectively, in winter half year. By comparing the characteristics of ISOs in El Ni?o and La Ni?a, a physical mechanism is proposed to explain the asymmetric responses of the precipitation over China toENSOin winter half year. In El Ni?o episodes, over western North Pacific (WNP) and South China Sea (SCS) the ISOs are inactive and exert little effect on the water vapor transport and convergence, inducing the positive precipitation anomalies with statistical significance over southern China in El Ni?o episodes. In La Ni?a episodes, however, the ISOs are active, which weaken the interannual variation signals of ENSO over WNP and southern China and lead to the insignificance of the interannual signals related to ENSO. Therefore, the asymmetric responses of precipitation over China to ENSO in winter half yearare possibly caused by the difference of intraseasonal oscillations over WNP and SCS between El Ni?o and La Ni?a. |
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