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Climate Prediction Center Ocean Briefing August scientific highlights |
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August 9, 2018 The NWS Climate Prediction Center Ocean Briefing makes monthly assessment of how the state of the global ocean evolved recently, what was the interaction with the atmosphere, and how the predictions were made for the future. To facilitate understanding of the science embedded in the forecast, it highlights important ongoing physical and dynamical processes for potential development. This month's ocean briefing led by Dr. Caihong Wen highlighted 1) current ENSO conditions compared with historical events, 2) Atlantic Multi-decadal Oscillation (AMO) related North Atlantic SST and ocean heat content evolution and the link to weak North Atlantic hurricane activities, and 3) capability of the new CPC pentad (5-day mean) Sea Surface Salinity (SSS) product in capturing meso-scale dynamical signals related to tropical instability wave (TIW), which plays an important role in air-sea interactions and subseasonal-to-seasonal (S2S) climate variability (Wen et al. 2012). The briefing material can be accessed at |
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Reference Wen, C., Y. Xue, and A. Kumar, 2012: Ocean–Atmosphere Characteristics of Tropical Instability Waves Simulated in the NCEP Climate Forecast System Reanalysis. J. Climate, 25, 6409–6425. DOI: 10.1175/JCLI-D-11-00477.1 |
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North American Multi-Model Ensemble Teleconference The impact of SST-forced and unforced teleconnections on 2015/16 El Niño winter precipitation over the western U.S. August 2, 2018 The ongoing discussion of the difficult prediction of anomalous dry conditions over Southern California during the 2015/16 El Niño winter was continued by Dr. Young-Kwon Lim of the Global Modeling and Assimilation Office, NASA Goddard Space Flight Center. Earlier contributions to this discussion were provided by Arun Kumar (4/5/18) and Huug van den Dool (6/14/18). In addition to finding that the spatial distribution of the tropical Pacific warming in 2015/16 was not a main cause of the negative precipitation anomalies in Southern California (agreeing with previous researchers), Dr. Lim showed that the atmospheric response to the Northeast Pacific warm water blob (WWB) SST could decrease precipitation in the Southwestern U. S. region, and the model response to the WWB was not sufficient to fully overcome the relatively large El Niño-driven positive precipitation anomalies. Regarding the role played by internal atmospheric variability, further regressing the intra-ensemble variance of the precipitation against the leading height modes produced precipitation anomalies that did much to close the gap between the observed and ensemble mean response, especially in the Southwest where the AO/NAO-like leading noise pattern was seen to play a key role. No NMME models predicted the negative precipitation anomalies over Southern California; rather, all of them displayed a strong and predictable response to the tropical Pacific SST forcing. “It may not represent a failure of the forecasts, but a failure to adequately provide the community with a quantifiable and understandable measure of the uncertainty in the prediction”, Dr. Lim said in conclusion. Reference Lim, Y.-K., S. D. Schubert, Y. Chang, A. M. Molod, and S. Pawson, 2018: The impact of SST-forced and unforced teleconnections on 2015/16 El Niño winter precipitation over the western US. J. Climate, 31, 5825-5844, doi:10.1175/JCLI-D-17-0218.1. |
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