Abrupt ending of MJO by CCKW precipitation leaves swath of flooding across Indonesia

Senior, Natasha V., Matthews, Adrian J., Webber, Benjamin G. M., Paski, Jaka A. I., Nuryanto, Danang E., Jones, Richard W., Permana, Donaldi S. and Febriyanti, Auliya'a H. (2025) Abrupt ending of MJO by CCKW precipitation leaves swath of flooding across Indonesia. Quarterly Journal of the Royal Meteorological Society. ISSN 0035-9009 (In Press)

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Abstract

Convectively coupled Kelvin waves (CCKWs) are eastward propagating weather systems that locally organise convection and are linked to precipitation extremes across the Maritime Continent (MC). They are often embedded in active Madden-Julian Oscillation (MJO) phases. The MJO also propagates eastwards but influences convection in the MC over longer timescales and larger areas. This paper examines a case study during July 2021 of multiple CCKWs and westward propagating inertio-gravity waves (WIGs) embedded within an active MJO. The final CCKW traversed the western MC causing precipitation extremes across equatorial Indonesia and East Malaysia that led to numerous reports of flooding and landslides, with western Borneo the worst affected region. The MJO event was abruptly terminated following the passage of this CCKW. Analysis of the total column water budget reveals that the precipitation rate exceeded the vertically integrated moisture flux convergence provided by the CCKW, drying out the atmosphere and suppressing further convection. The performance of the UK Met Office prediction model was evaluated for this case study; parameterised convection configurations generally performed as well as or better than explicit convection models. This is possibly because they better represented the location and timing of the convective systems that developed because of interactions between the CCKWs and WIGs. This research highlights how CCKWs should not simply be viewed as convective systems that locally affect weather, but as having the potential to deliver larger-scale impacts over the entire equatorial Maritime Continent, when part of a complex multiscale interaction. Such interactions can involve the MJO influencing CCKWs downscale by providing enhanced convection. Conversely, the suppressed phase of CCKWs can dampen the MJO convective signal and terminate MJO propagation. Whilst weather prediction models may accurately forecast rainfall associated with individual equatorial modes, capturing their combined effect remains a challenge.

Item Type:	Article
Additional Information:	Data Availability Statement: Data used in this study are publicly available. CCKW trajectories are available through github.com/adrianjmatthews/CCKW_database. The IMERG precipitation data were supplied by the National Aeronautics and Space Administration through their website at gpm.nasa.gov. ERA5 data were accessed from Copernicus at cds.climate.copernicus.eu (doi: 10.24381/cds/bd0915c6). Disaster event reports were supplied by ADInet and are available through their website at adinet.ahacentre.org. MetUM forecast data were supplied by Met Office, UK and are available at zenodo.org/records/12760373 (doi: 10.5281/zenodo.12760372). Funding information: This work and its contributors (NVS, AJM and BGMW) were supported by the Met Office Weather and Climate Science for Service Partnership (WCSSP) Southeast Asia as part of the Newton Fund (award P110707), and AJM was supported through the TerraMaris project, funded by the Natural Environment Research Council (award NE/R016704/1).
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Climatic Research Unit University of East Anglia Schools > Faculty of Science > Tyndall Centre for Climate Change Research Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research Faculty of Science > Research Groups > Fluids & Structures Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	LivePure Connector
Date Deposited:	08 Apr 2025 13:30
Last Modified:	10 Apr 2025 16:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/98991
DOI:	10.1002/qj.4997

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