热带大气低频振荡强度年际异常对中国东部冬季降水的影响

IMPACT OF THE INTERANNUAL VARIABILITY OF THE LOW-FREQUENCY OSCILLATION INTENSITY IN THE TROPICS ON THE WINTERTIME RAINFALL IN EAST CHINA

利用NOAA的逐日向外长波辐射(OLR)资料、NCAR/NCEP资料和中国台站降水资料,以低频振荡的能量与总能量的百分比作为低频振荡强度指数,初步研究了热带地区低频振荡强度的年际变化及其对中国东部冬季降水的影响。结果表明:冬季热带地区低频振荡强度高(低),则我国东部冬季降水多(少)。热带低频振荡强度的年际变化与欧洲西北部到我国南部的波列及东亚冬季风的年际变化密切相关。在热带低频振荡强度高值年,冬季北非槽和孟加拉湾槽加深,东亚大槽减弱,东亚冬季风减弱,我国东部地区南风异常,水汽输送强,导致降水偏多;反之,在热带低频振荡强度低值年,北非槽和孟加拉湾槽减弱,东亚大槽加深,东亚冬季风加强,我国东部地区北风异常,水汽输送减弱,导致降水偏少。

Using the percentage of the low-frequency oscillation energy and the total energy as the low-frequency oscillation intensity index, the association of the interannual variability of low-frequency oscillation intensity with rainfall in the area of East China in the boreal winter is investigated based on NOAA outgoing longwave radiation （OLR） data, NCAR/NCEP data and observed precipitation data of 160 stations in China. The results demonstrated that when the tropical low-frequency oscillation intensity is high （low）, the precipitation in East China is more （less）. The results also showed that the interannual variability of low-frequency oscillation intensity is linked to the interannual variability of both subtropical wave trains and East Asian Winter Monsoon. In the high-value years of the low-frequency oscillation intensity, the North Africa trough and the Bay of Bengal trough deepen, East Asia trough and East Asian Winter Monsoon weaken, the south wind anomaly appears in East China, and the moisture increases, leading to more rainfall. In the low-value years of the low-frequency oscillation intensity, the North Africa trough and the Bay of Bengal trough weaken, East Asia trough and East Asian Winter Monsoon deepen, the north wind anomaly appears in East China, and the moisture decreases, resulting in less rainfall.