We investigate how the Madden-Julian Oscillation (MJO), the dominant mode of tropical subseasonal variability, modulates the lifecycle of cool-season North Pacific atmospheric rivers (ARs). When the enhanced (suppressed) convection center is located over the Indian Ocean (western Pacific), more AR events originate over eastern Asia and with fewer over the subtropical northern Pacific. When the enhanced (suppressed) convection is over the western Pacific (Indian Ocean), the opposite changes occur, with more AR events originate over the subtropical northern Pacific and fewer over eastern Asia. Dynamical processes involving anomalous MJO wind and seasonal mean moisture are found to be the dominant factors impacting these variations in AR origins. The MJO-related anomalous geopotential height patterns are also shown to modulate the propagation of the AR events. These MJO–AR lifecycle relationships are further supported by model simulations.
Bibliographical noteFunding Information:
The authors would like to acknowledge the two anonymous reviews for their constructive and thoughtful comments about our manuscript. Y. Zhou was supported by NSF grant AGS-1652289 and the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Climate and Environmental Sciences Division, Regional & Global Climate Modeling Program, under Award DE-AC02-05CH11231. H. Kim was supported by NSF grant AGS-1652289 and the KMA R&D Program grant KMI2018-03110. D.E.W.'s contribution to this study was carried out on behalf of the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The authors thank Dr. Aneesh Subramanian for sharing the ECMWF AMIP simulation data.
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- Madden-Julian Oscillation
- atmospheric river
- lifecycle tracking
- moisture transport