The decadal shift of the long persistent rainfall over the northern part of China and the associated ocean conditions

摘要

The long persistent rainfall (LPR) over the northern part of China has a great impact on its society and economics. This study investigates the decadal shift of the regional-mean LPR frequency over the northern part of China (LPR frequency) from 1971 to 2014 and the associated ocean conditions. The LPR frequency has experienced a significant decadal shift around 1996, with an enhanced (reduced) anomaly before (after) 1996, which is closely associated with a meridional tri-pole sea surface temperature (SST) anomaly over the central Pacific, a La Nina-like anomaly for the pre-1996 epoch (1971-1996) and an obvious warming over the south Indian Ocean and the western part of south Pacific Ocean in the post-1996 epoch (1997-2014). In the pre-1996 epoch, associated with the typical SSTs, the ascent motion with increasing humidity anomalies are over the northern part of China. Meanwhile, high (low) pressure anomalies are over western Asia and East Asia (Europe and central Asia), which resembles as the positive phase of the Silk Road pattern (SRP). It would be associated with the polewards shift of the East Asian jet stream (EAJS) and therefore result in the northwards shift of the rain belt and benefit the occurrence of the LPR. In the post-1996 epoch, associated with the warming over the specific south oceans, a descend anomaly dominates over the northern part of China, as well as the resembled negative phase of the SRP over mid-high latitudes and equatorwards shift of the EAJS. These would suppress the rainfall over the northern part of China and reduce the LPR frequency over there after 1996.