Frequency features of spring continuous rain over southern China and its previous circulation signals
In this paper,the frequency variation of spring persistent rain(SPR) and its relationship with previous East Asian subtropical jet and polar front jet are investigated.The results indicate that the SPR is the longer-persistent (more than 4 days) rainfall event which is identified as Spring Continuous Rain (SCR)over southern China and usually occurs in the region of 22.5 °N-30 °N,105 °E-120 °E and spans in 13th-27th pentads.Decreasing tendency of SCR is evident in the whole southern China and a quite consistent interannual variation covers the entire region.A homogenous pattern can be identified for the spatial-temporal variation.The principal component contains multi-time scales,and the primary one is the interannual variability.During the period of 10 d to 35 d before the 13th pentad,when persistent weakening polar front jet and northward movement of subtropical jet simultaneously exist,it becomes prior signal of easy occurrence of SCR.
Spring continuous rainFrequencySubtropical jetPolar front jet