黄河流域秋季降水及环流对ENSO和IOD的响应分析

Response Analysis of Precipitation in the Yellow River Basin and the Circulation in Autumn to ENSO and IOD

利用1961 2011年NCEP/NCAR再分析资料和黄河流域54站降水资料,通过讨论印度洋偶极子IOD独立发生时及IOD与ENSO联合发生时黄河流域秋季降水的差异,研究了秋季降水及环流对ENSO和IOD的响应情况。结果表明:1)仅有IOD发生时,其正位相年使得黄河流域的秋季降水相应为正异常。2)当IOD与ENSO伴随出现时,无论IOD是正位相年还是负位相年,只要和El Nino同时发生,黄河流域秋季降水都表现为负异常;和La Ni-na同时发生时,黄河流域秋季降水都表现为正异常。有无ENSO发生,IOD与秋季降水的关系有很大差异。3)欧亚中纬度地区500 hPa高度东高西低距平场形势和850 hPa黄河流域中下游南风距平异常,是黄河流域秋季降水正异常的主要环流成因。4)依据秋季海温与夏季海温相关性,可以把夏季ENSO和IOD异常信号特征作为先兆信号之一来预测秋季降水趋势。

Based on the NCEP/NCAR reanalysis data and the rainfall data of 54 stations in the Yellow river basin from 1961 to 2011,discussed the difference of autumn precipitation of the IOD independent occurrence and the IOD in combination with ENSO occurrence,and investigated the IOD and ENSO response to the autumn precipitation in the Yellow river basin and the circulation.The results as followed.1）Only the IOD occurrence,the positive phase makes the Yellow river basin precipitation in autumn the corresponding positive anomaly.2）When the IOD accompanied with ENSO occurrence,whether the IOD was the positive phase and negative phase,but there were El Nino events simultaneously,the precipitation in the Yellow river basin in autumn was negative anomaly;and there were La Nina events,the precipitation in the Yellow river basin in autumn is positive anomaly;the relationship between the precipitation in the Yellow river basin in autumn and the IOD is very difference when ENSO occurred or no.3）The major circulation reasons of the precipitation in the Yellow river basin in autumn were the west high and east low in 500 hPa height anomaly field in Eurasia and the south wind anomaly in 850 hPa wind anomaly field in the middle and lower reaches of the Yellow river.4）Based on the relationship between the sea surface temperature in autumn and summer,the ENSO and IOD unusual signal could be regard as the early signal to predict precipitation in autumn.