Important role of North Atlantic air-sea coupling in the interannual predictability of summer precipitation over the eastern Tibetan Plateau

Tibetan Plateau (TP) summer precipitation, whose first leading mode presents a dipole oscillation between the northeastern and southeastern TP, plays important roles in the water cycle and atmospheric circulation. Using a weakly coupled data assimilation (WCDA) system to constrain the atmospheric component in a coupled model with a global atmospheric reanalysis product, this study demonstrates significant improvements in predicting the interannual variation of summer precipitation over the eastern TP, capturing the strong reversal mode between the northeastern and southeastern TP. These improvements are mainly attributed to the strong air-sea coupling over the North Atlantic (NA) and its remote impacts on the TP precipitation. This coupling allows observation-constrained atmosphere to significantly influence initial conditions (ICs) of sea surface temperature (SST) in the NA area and then obviously affect predictions of both NA SST and summer North Atlantic Oscillation (SNAO), which affects the downstream TP atmospheric circulation through the wave train of Eliassen-Palm (EP) stationary wave flux. This study highlights the importance of NA air-sea coupling in the interannual predictability of TP precipitation and suggests a new source of interannual predictability of TP precipitation.