江淮流域旱涝年夏季降水与东亚季风区低频OLR的变化特征

Variation characteristics of OLR LFO in monsoon region of east Asia and its relationship with precipitation of Yangtze-Huathe River

用美国NOAA卫星提供的1974-2004年逐日OLR资料，选取江淮流域典型旱涝年进行合成分析，再利用Butterworth带通滤波器进行滤波，分别得到旱涝年30～60d的OLR低频分量，并分析了旱涝年夏季OLR及其低频振荡分布特征与传播差异，最后研究了夏季青藏高原南侧与华北地区OLR低频变化与江淮降水的关系，结果表明：旱涝年夏季东亚地区OLR低频分量的经纬向传播差异是造成江淮地区夏季旱涝的原因之一；典型早年江淮流域降水与青藏高原南侧逐候的OLR低频分量显著正相关，而在典型涝年则是负相关；华北地区存在负（正）OLR低频分量可能导致滞后其20d的江淮流域降水偏少（多）。

By using the CAC daily outgoing long wave radiation （OLR） data, the representative droughts and floods are chosen, and 30-60 day low-frequency oscillation （LFO） of OLR is found by the band-pass filter. Then the different distribution characteristics and propagation of the OLR and OLR-LFO in summer are analyzed. Finally, the relationship between the OLR-LFO in Southern Tibetan Plateau, north China and the rainfall in Yangtze and Huaihe River area are studied. The results show that： in drought years OLR as well as OLR-LFO is remarkably different compared to the cases in flood years, and the different precipitation may be caused by the different meridional and zonal-travelling of the OLR- LFO; there is close positive correlation between the Southern Tibetan Plateau and the rainfall in representative drought years, however it is negative in flood years; positive/negative OLR-LFO of north China can lead to the twenty days lagged abnormal drought/flood in the Yangtze and Huaihe River.