Enhanced Seasonal Predictability of Spring Soil Moisture over the Indo-China Peninsula for Eastern China Summer Precipitation under Non-ENSO Conditions

Seasonal prediction of summer precipitation over eastern China is closely linked to the East Asian monsoon circulation, which is largely affected by the El Nino-Southern Oscillation (ENSO). In this study, results show that spring soil moisture (SM) over the Indo-China peninsula (ICP) could be a reliable seasonal predictor for eastern China summer precipitation under non-ENSO conditions. When springtime SM anomalies are present over the ICP, they trigger a structured response in summertime precipitation over most of eastern China. The resultant south-to-north, tri-polar configuration of precipitation anomalies has a tendency to yield increased (decreased) precipitation in the Yangtze River basin and decreased (increased) in South and North China with a drier (wetter) spring soil condition in the ICP. The analyses show that ENSO exerts a powerful control on the East Asian circulation system in the ENSO-decaying summer. In the case of ENSO forcing, the seasonal predictability of the ICP spring SM for eastern China summer precipitation is suppressed. However, in the absence of the influence of ENSO sea surface temperature anomalies from the preceding winter, the SM anomalies over the ICP induce abnormal local heating and a consequent geopotential height response owing to its sustained control on local temperature, which could, in turn, lead to abnormal eastern China summer precipitation by affecting the East Asian summer monsoon circulation. The present findings provide a better understanding of the complexity of summer climate predictability over eastern China, which is of potential significance for improving the livelihood of the people.