East African Monsoon as a Drawbridge for the Circumnavigation of Madden–Julian Oscillation Events

Journal Article · 15 June 2023 · Geophysical Research Letters

DOI: https://doi.org/10.1029/2023gl102906 · OSTI ID:1994848

Hagos, Samson  ^[1]; Jung, Jia ^[1]; Ma, Po‐Lun  ^[1]; Lubis, Sandro W.  ^[1]; Balaguru, Karthik  ^[1]; Chang, Chuan‐Chieh (Jay) ^[1]; Leung, L. Ruby  ^[1]

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1. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

The seasonality of circumnavigation of Madden-Julian Oscillation (MJO) events is examined using 42 years of observations and global model simulations. MJO events are most likely to propagate across the Atlantic Ocean, Africa and back to equatorial Indian Ocean relatively unweakened during March-April-May and to a lesser extent in October-November-December. These seasons correspond to the "long-rain" and "short-rain" periods of East African monsoon when precipitation over Africa is near the equator and extend farthest east toward Indian Ocean. Moisture budget analysis of a circumnavigating MJO event under real and hypothetical seasonally varying background conditions indicates that the seasonal zonal movement of zonal component of background circulation regulates the moistening of MJO crossing from Eastern Africa to Indian Ocean. Ensembles of Energy Exa-scale Earth System Model (E3SM) simulations of the MJO event under idealized seasonally varying background state confirm the observed drawbridge-like role of East African monsoon in the propagation of MJO.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC05-76RL01830; AC02-05CH11231
• OSTI ID: 1994848
• Report Number(s): PNNL-SA-185746; {"","Journal ID: ISSN 0094-8276"}
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 12 Vol. 50; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English