An Extratropical Pathway for the Madden–Julian Oscillation’s Influence on North Atlantic Tropical Cyclones

Journal Article · Fri Dec 15 00:00:00 EST 2023 · Journal of Climate

DOI:https://doi.org/10.1175/JCLI-D-23-0251.1· OSTI ID:2221912

Chang, Chuan-Chieh  ^[1]; Lubis, Sandro W. ^[1]; Balaguru, Karthik ^[1]; Leung, L. Ruby ^[1]; Hagos, Samson M. ^[1]; Klotzbach, Philip J. ^[2]

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1. a Pacific Northwest National Laboratory, Richland, Washington
2. b Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado

Abstract This study investigates the combined impacts of the Madden–Julian oscillation (MJO) and extratropical anticyclonic Rossby wave breaking (AWB) on subseasonal Atlantic tropical cyclone (TC) activity and their physical connections. Our results show that during MJO phases 2–3 (enhanced Indian Ocean convection) and 6–7 (enhanced tropical Pacific convection), there are significant changes in basinwide TC activity. The MJO and AWB collaborate to suppress basinwide TC activity during phases 6–7 but not during phases 2–3. During phases 6–7, when AWB occurs, various TC metrics including hurricanes, accumulated cyclone energy, and rapid intensification probability decrease by ∼50%–80%. Simultaneously, large-scale environmental variables, like vertical wind shear, precipitable water, and sea surface temperatures become extremely unfavorable for TC formation and intensification, compared to periods characterized by suppressed AWB activity during the same MJO phases. Further investigation reveals that AWB events during phases 6–7 occur in concert with the development of a stronger anticyclone in the lower troposphere, which transports more dry, stable extratropical air equatorward, and drives enhanced tropical SST cooling. As a result, individual AWB events in phases 6–7 can disturb the development of surrounding TCs to a greater extent than their phases 2–3 counterparts. The influence of the MJO on AWB over the western subtropical Atlantic can be attributed to the modulation of the convectively forced Rossby wave source over the tropical eastern Pacific. A significant number of Rossby waves initiating from this region during phases 5–6 propagate into the subtropical North Atlantic, preceding the occurrence of AWB events in phases 6–7.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); G. Unger Vetlesen Foundation
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 2221912
• Alternate ID(s): OSTI ID: 2274892
• Report Number(s): PNNL-SA-184405
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Vol. 36 Journal Issue: 24; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Madden-Julian oscillation
Rossby waves
wave breaking
tropical cyclones