Insights into the Causes and Predictability of the 2022/23 California Flooding

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dc.contributor.authorSchubert, Siegfried D.
dc.contributor.authorChang, Yehui
dc.contributor.authorDeAngelis, Anthony M.
dc.contributor.authorLim, Young-Kwon
dc.contributor.authorThomas, Natalie
dc.contributor.authorKoster, Randal D.
dc.contributor.authorBosilovich, Michael G.
dc.contributor.authorMolod, Andrea M.
dc.contributor.authorCollow, Allison
dc.contributor.authorDezfuli, Amin
dc.date.accessioned2024-05-06T15:05:50Z
dc.date.available2024-05-06T15:05:50Z
dc.date.issued2024-03-25
dc.description.abstractIn late December of 2022 and the first half of January 2023 an unprecedented series of atmospheric rivers (ARs) produced near record heavy rains and flooding over much of California. Here we employ the NASA GEOS AGCM run in a “replay” mode, together with more idealized simulations with a stationary wave model, to identify the remote forcing regions, mechanisms and underlying predictability of this flooding event. In particular, the study addresses the underlying causes of a persistent positive Pacific/North American (PNA) - like circulation pattern that facilitated the development of the ARs. We show that that pattern developed in late December as a result of vorticity forcing in the North Pacific jet exit region. We further provide evidence that this vorticity forcing was the result of a chain of events initiated in mid-December with the development of a Rossby wave (as a result of forcing linked to the MJO) that propagated from the northern Indian Ocean into the North Pacific. As such, both the initiation of the event and the eventual development of the PNA depended critically on internally-generated Rossby wave forcings, with the North Pacific jet playing a key role. This, combined with contemporaneous SST (La Niña) forcing that produced a circulation response in the AGCM that was essentially opposite to the positive PNA, underscores the fundamental lack of predictability of the event at seasonal time scales. Forecasts produced with the GEOS coupled model suggests that useful skill in predicting the PNA and extreme precipitation over California was in fact limited to lead times shorter than about 3 weeks.
dc.description.sponsorshipThis work was supported by the NASA MAP (NNG17HP01C and 80NSSC21K1729) program and the National Climate Assessment Enabling Tools project at NASA’s Global Modeling and Assimilation Office (GMAO). MERRA-2 data were developed by the NASA GMAO at the Goddard Space Flight Center (GSFC) under funding by the NASA MAP program. The file specifications for the MERRA-2 output are documented in Bosilovich (2016). The various MERRA-2 fields used for this study (GMAO 2015a; 2015b; 2015c; 2015d) include precipitation that is corrected with gauge and satellite observations (Reichle et al. 2017). Computational resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Center for Climate Simulation (NCCS) at GSFC.
dc.description.urihttps://journals.ametsoc.org/view/journals/clim/aop/JCLI-D-23-0696.1/JCLI-D-23-0696.1.xml
dc.format.extent41 pages
dc.genrejournal articles
dc.identifierdoi:10.13016/m2rxfn-uno4
dc.identifier.citationSchubert, Siegfried D., Yehui Chang, Anthony M. DeAngelis, Young-Kwon Lim, Natalie P. Thomas, Randal D. Koster, Michael G. Bosilovich, Andrea M. Molod, Allison Collow, and Amin Dezfuli. “Insights into the Causes and Predictability of the 2022/23 California Flooding.” Journal of Climate 1, no. aop (March 25, 2024). https://doi.org/10.1175/JCLI-D-23-0696.1.
dc.identifier.urihttps://doi.org/10.1175/JCLI-D-23-0696.1
dc.identifier.urihttp://hdl.handle.net/11603/33596
dc.language.isoen_US
dc.publisherAMS
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC GESTAR II
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rightsPublic Domain
dc.rights.urihttps://creativecommons.org/publicdomain/mark/1.0/
dc.titleInsights into the Causes and Predictability of the 2022/23 California Flooding
dc.typeText
dcterms.creatorhttps://orcid.org/0000-0002-6433-7257
dcterms.creatorhttps://orcid.org/0000-0002-3566-3889
dcterms.creatorhttps://orcid.org/0000-0003-3274-8542

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