近400年澜沧江源区年平均流量周期特征及其对厄尔尼诺的响应

本文基于重建的1595~2006年澜沧江源区年平均流量(澜沧江流量)和NOAA古气候资料,应用MTM-SVD方法对澜沧江流量周期变化规律及其对厄尔尼诺的响应进行了分析。结果表明,近400年澜沧江流量与厄尔尼诺有显著负相关,在年代际的13.5年和年际的5年周期上存在显著协同变化,并且分别对当年春末和上年秋初的大气环流有很好的响应。在13.5年和5年典型循环过程中,二者都表现出反位相的对应关系,当厄尔尼诺指数偏低(高)时,澜沧江流量偏多(少)。但是进一步分析海温异常空间分布,发现在13.5年周期中,澜沧江流量主要受中部型厄尔尼诺事件影响,而在5年周期循环中,澜沧江流量则主要受东部型厄尔尼诺事件调控。在13.5年典型周期循环中,中部型厄尔尼诺会引起双圈沃克环流异常,同时激发PJ(太平洋-日本涛动)遥相关波列,并影响澜沧江源区气温和降水,从而导致澜沧江流量异常;在5年周期循环中,东部型厄尔尼诺会引起单圈沃克环流异常,同时激发EU(欧亚)遥相关波列,进而影响澜沧江流量变化。

PERIODIC CHARACTERISTICS OF ANNUAL MEAN FLOW IN LANCANG RIVER SOURCE AREA IN RECENT 400 YEARS AND ITS RESPONSE TO El Nino

Periodic characteristics of the annual average flow of Lancang River(AFLR)and the response to El Niño are examined using the hydrological data of Xiangda(32.75°N,96.75°E),meteorological data of Nangqian(32.2°N,96.47°E)and Zaduo(32.88°N,95.28°E),reconstructed AFLR data,NOAA Paleoclimatic data and the Multi-Taper Method-Singular Value Decomposition(MTM-SVD)method.Results show that there is a significant negative correlation between AFLR in the source area and El Niño during 1595~2006.There are significant synergistic variations in 13.5-a and 5-a cycles,and they respond well to the atmospheric circulation in late spring and early autumn,respectively.During the typical cycle of 13.5-a and 5-a,both of them show the corresponding inverse phase relationship,when the El Niño index is low,the AFLR is high,and vice versa.However,from the distribution pattern of SSTA anomalies,there are significant differences between the two typical cycles.In the interdecadal 13.5-a cycle,the AFLR is mainly affected by the middle-type El Niño events,while in the interannual 5-a cycle,the AFLR is mainly regulated by the eastern-type El Niño events.In the typical 13.5-a cycle,the middle El Niño caused the double-loop Walker circulation anomaly,triggered the PJ telecorrelation wave train,and affected the temperature and precipitation in the source area of the Lancang River,thus causing the flow anomaly of the Lancang River.During the 5-a cycle,the eastern El Niño leads to the one-loop Walker circulation anomaly and triggers the EU telecorrelation wave train,which affects the flow variation of the Lancang River.