Remote Influence of Southern Tibetan Plateau Heating on North Pacific Atmospheric Rivers

Abstract This study examines the remote influence of the Tibetan Plateau (TP) diabatic heating on atmospheric river (AR) activity in the North Pacific. First, we identify a sensitive heating region on the southern TP establishing a positive correlation between its heating and AR frequency. This correlation is attributed to latent heat release supported by a substantial moisture supply. Further analysis reveals that the dynamic effect of the eastward-propagating Rossby waves, originating from the Atlantic Ocean and modulated by the TP, facilitates upward moisture lifting. Using the Water Accounting Model-2Layers, we demonstrate that this anomalous heating is primarily due to increased moisture from the Indian Ocean, the Arabian Sea, and the Bay of Bengal, amplified by the westward extension of the western North Pacific subtropical high (WNPSH). Additional moisture contributions are observed from Eurasia. Moreover, Rossby wave activity over the TP propagates to the east of Japan, enhancing westerlies with upper-level divergence field which develops a cyclonic and anticyclonic vortex structure. This structure attracts abundant moisture to the North Pacific, thereby increasing AR activity. This study also highlights a positive feedback mechanism involving the southern TP heating and the eastward-propagating upper-level anticyclone, which enhance the western extension of the WNPSH. These findings underscore the global climatic impacts of the TP, emphasizing its role as a critical factor in AR dynamics across the North Pacific. Significance Statement This study explores the remote impact of the Tibetan Plateau (TP) heating on the atmospheric river (AR) in the North Pacific. Our findings indicate that southern TP heating resulting from remote moisture contribution, quantitatively assessed using Water Accounting Model-2Layers, coupled with the western extension of the western North Pacific subtropical high (WNPSH) and sea surface temperature warming anomaly as well as the eastward-propagating Rossby waves derived from the Atlantic Ocean, plays a crucial role in AR activity in the North Pacific. TP heating affects Rossby waves propagating east of Japan enhancing the westerlies and the easterlies. Moreover, the coupled divergence and cyclonic vortex structures attract more moisture toward the North Pacific fostering AR activity. Additionally, the interplay between southern TP heating and WNPSH builds a positive feedback mechanism.