Remote modulation of sub-seasonal soil moisture on clustered extreme precipitation in Northern China

Clustered extreme precipitation (CEP) events draw worldwide attention due to their non-neglectable impacts on socio-economic activities. This study focuses on the typical circulations associated with CEP events in Northern China and investigates the role of hydro-thermal processes over Eurasia. Based on the Self-organizing map method, there are two types of circulations closely related to the occurrence of CEP events over Northern China. One of them features a short wave and a subtropical high. Another shows a northern cyclone and high pressure around the sea of Okhotsk. The anomalous soil moisture (SM) over the Eastern Caspian Sea (ECS) and Northern Tibet Plateau (NTP) at the quasi-biweekly time scale dominates the typical circulations and CEP events over Northern China, rather than local forcing. On the one hand, decreased SM over the ECS induces the eastward movements of short-wave disturbances, along with the westward extension of the strengthened Western Pacific Subtropical High, favoring the increased precipitation over Northern China. On the other hand, increased SM over the NTP contributes to the meridional circulation and enhanced long-wave ridge, coupled with the northern cyclone at the lower level, finally leading to increases in precipitation over Northern China. The results may be useful for the predictions of CEP events in Northern China.