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Atmospheric Rivers (ARs), corridors of intensive water vapor transport, have received much attention recently due to their potentially large economic and societal impacts. However, a comprehensive understanding of the interannual variability of ARs over East Asia is still lacking. This study examines the frequency of AR occurrence over East Asia based on the EAR5 reanalysis. It is shown that the frequency of AR occurrence over East Asia displays obvious seasonality, with its peak in early boreal summer. ARs contribute to up to 50% of total precipitation and largely modulate the interannual variability of precipitation in East Asia during early boreal summer. The interannual variability of ARs over East Asia during early boreal summer is largely controlled by the Indo-western Pacific Ocean Capacitor (IPOC) effect, which is mainly triggered by El Niño-Southern Oscillation and sometimes by Indian Ocean dipole. During early boreal summer, a higher frequency of AR occurrence over East Asia is associated with anomalous anticyclonic circulation (AAC) over the Indo-western Pacific region. The AAC, the atmospheric signal of the IPOC mode, indicates an enhanced East Asian summer monsoon and a northwestward shift of the western North Pacific subtropical high, favoring the AR occurrence over East Asia. This study illustrates that a strong positive Indian Ocean dipole event could impact AR activity over East Asia in the following summer by triggering the IPOC effect. The IPOC-related signals 2–4 months ahead could be useful to predict the AR occurrence over East Asia during early boreal summer. [ABSTRACT FROM AUTHOR]

In this study, daily outgoing longwave radiation (OLR) product is used to detect the atmospheric intraseasonal oscillation (ISO) in the eastern tropical Indian Ocean (TIO). A 50–80-day ISO is identified south of the equator, peaking in boreal winter and propagating eastward. The mechanisms underneath are investigated using observational data and reanalysis products. The results suggest that the 50–80-day atmospheric ISO is enhanced by ocean dynamic processes during December–January. Monsoon transition in October–November causes large wind variability along the equator. Equatorial sea surface height/thermocline anomalies appear off Sumatra due to the accumulative effects of the wind variability, leading the atmospheric 50–80-day ISO by ~ 5–6 weeks. The wind-driven ocean equatorial dynamics are reflected from the Sumatra coast as downwelling oceanic Rossby waves, which deepen the thermocline and contribute to the SST warming in the southeastern TIO, affecting local atmospheric conditions. It offers insights into the role of ocean dynamics in the intensification of 50–80-day atmospheric ISOs over the eastern TIO and explains the seasonal peak of the eastward-propagating ISO during boreal winter. These results have implications for intraseasonal predictability. [ABSTRACT FROM AUTHOR]

Based on ERA-interim reanalysis dataset from 1979 to 2018, this study revisits the global and regional water cycle, as well as the water vapor transport between ocean basins. The surface of the Earth is divided into five continents and four ocean basins, water vapor budget, and its seasonal variability of each continent and ocean basin are calculated. The Indian Ocean and the Atlantic are major net water vapor source regions, ~ − 0.47 Sv and ~ −0.82 Sv, respectively, while the Pacific and the Arctic are weak net water vapor sink regions, ~ 0.04 Sv and ~ 0.06 Sv, respectively. A total of 85% of evaporation and 78% of precipitation occur at the ocean-atmosphere interface while 15% of evaporation and 22% of precipitation occur at the land-atmosphere interface. About 1.19 Sv water vapor is carried out from oceans to lands. The water vapor transport is about 0.07 Sv from the Indian Ocean to the Pacific, and 0.22 Sv from the Atlantic to the Pacific through the segments. At low latitudes, both the Atlantic and the Indian Ocean transport water vapor to the Pacific, with a total of 0.29 Sv. Those results update the estimate of global and regional water vapor budget. [ABSTRACT FROM AUTHOR]