Possible mechanism of south-north reverse of early summer precipitation on the Tibetan Plateau

Based on the monthly average precipitation data from meteorological stations on the Tibetan Plateau (TP), this study reveals the spatial distribution characteristics of the north-south reverse early summer (May-June) precipitation during 1979–2019. Through analysis of the circulation patterns associated with early summer precipitation, we find that the interannual variation of the precipitation on the TP is closely related to the meridional wind around the 32.5°N (I_TPv). The results indicate that during anomalously strong (weak) I_TPv, the TP is dominated by southerly (northerly) wind anomalies, resulting in more (less) precipitation in the northern and less (more) precipitation on the southern TP. The pattern is attributed to water vapor convergence and divergence in the northern and southern regions of TP, respectively. The meridional wind anomaly is linked to anomalous strong (weak) southwesterly winds in the southern upstream region and anomalous weak (strong) westerly winds in the northern upstream region of the TP.