ENSO发展和衰减阶段的陕西夏季降水异常特征

Characteristics of Shaanxi Summer Precipitation Anomalies in ENSO Developing and Decaying Stages

  • 摘要: 利用1961—2008年陕西78个气象站夏季 (6—8月) 降水资料、NCEP/NCAR位势高度场和风场月平均再分析资料,采用合成及相关分析方法探讨ENSO发展和衰减阶段对陕西夏季降水异常的影响,以期为陕西夏季降水的气候预测提供线索和依据。结果表明:陕西夏季降水异常对ENSO发展和衰减阶段的响应存在显著差异,El Niño发展阶段和La Niña衰减阶段,陕西夏季降水偏少; El Niño衰减阶段和La Niña发展阶段,陕西夏季降水偏多; ENSO不同阶段对陕西7月降水影响最为显著。比较而言,El Niño事件对陕西夏季降水的影响更加显著。在El Niño衰减、La Niña发展阶段,西太平洋副热带高压偏强、偏西,东亚夏季风偏弱,而在El Niño发展、La Niña衰减阶段,西太平洋副热带高压偏弱、偏东,东亚夏季风偏强,El Niño过程对东亚夏季风强弱的影响更加显著。ENSO发展和衰减阶段通过影响大气环流变化和东亚夏季风的强弱,进而影响陕西夏季降水。

     

    Abstract: Based on Shaanxi summer precipitation data from 1961 to 2008, NCEP/NCAR monthly reanalysis data, the influence of developing stage and decaying stage of ENSO events on Shaanxi summer precipitation is analyzed through composite analysis. It shows that the response of Shaanxi summer precipitation to ENSO in developing stage is very different from that of the decaying stage. During El Niño developing stage and La Niña decaying stage, the precipitation in Shaanxi is less than normal. During La Niña developing stage and El Niño decaying stage, Shaanxi has more precipitation than normal, and the most significantly impacted period by ENSO is July. The response of Shaanxi summer precipitation anomalies to La Niña developing stage and El Niño decaying stage is more remarkable than that of El Niño developing stage and La Niña decaying stage. There is a significant difference in atmospheric circulation in developing and decaying stages of ENSO, especially with regard to the western Pacific subtropical high and the East Asia monsoon strength. During El Niño developing stage and La Niña decaying stage, the western Pacific subtropical high is stronger and more west than normal and the East Asia monsoon is weaker than normal. During La Niña developing stage and El Niño decaying stage, the situation is the opposite. When the subtropical high is stronger and further west, Shaanxi has southwest wind anomalies which transport water vapor, the northern part has the north wind anomalies that bring cold air, and the precipitation would be higher. ENSO developing and decaying stages affect on the change of atmospheric circulation and the East Asia monsoon, and contribtute to Shaanxi summer precipitation. During El Niño developing stage and La Niña decaying stage, the East Asia monsoon is stronger, and Shaanxi has less precipitation. During La Niña developing stage and El Niño decaying stage, the East Asia monsoon is weaker and Shaanxi has more precipitation. In comparison, the East Asia summer monsoon is greatly affected by El Niño events than La Niña events. At the same time, Shaanxi summer precipitation is also affected by El Niño events more greatly. This is an evidence that ENSO affect Shaanxi summer precipitation through changing the East Asia summer monsoon strength.

     

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