Significant May-to-June Persistence of Precipitation in the Western Tibetan Plateau: Memory Effect of Local Soil Moisture

Abstract The western Tibetan Plateau (WTP) is a semi-arid area, yet its precipitation forms a critical component of the Asian Water Tower's hydrological cycle. This study has revealed that precipitation anomalies in WTP exhibit a significant persistence from May to June. Diagnostics of moisture budget and numerical experiments reveal that the precipitation in May primarily influences June precipitation through generating anomalous evaporation and the vertical gradient of specific humidity, caused by the memory effects of local soil moisture. It is further demonstrated that WTP is a hot spot of soil moisture-precipitation coupling, and the sensitivity of evaporation to soil moisture is particularly pronounced in June. Thus the phenomenon of ‘‘dry gets drier, wet gets wetter’’ occurs in WTP from May to June. This study deepens understanding of the subseasonal precipitation variability over WTP and provides a new perspective for predicting precipitation in early summer thereby considering the memory effects of underlying land process.