TY - JOUR
T1 - Assessing seasonal predictability sources and windows of high predictability in the climate forecast system, version 2
AU - Miller, Douglas E.
AU - Wang, Zhuo
N1 - Funding Information:
Acknowledgments. This work is supported by National Oceanic and Atmospheric Administration (NOAA) Grants NA15NWS4680007 and NA16OAR4310080, and Naval Research Laboratory Grant N00173-15-1-G004. The NOAA_OI_SST_V2 and GPCP data were provided by the NOAA/OAR/ESRL PSD (https://www.esrl.noaa. gov/psd/). We acknowledge the National Centers for Environmental Information (NCEI) for providing the CFSv2 and CFSR data, and thank the NCAR Computational and Information Systems Laboratory (CISL) for providing computing resources. We thank three anonymous reviewers for their comments and suggestions that helped strengthen the study.
Publisher Copyright:
© 2019 American Meteorological Society.
PY - 2019/2/1
Y1 - 2019/2/1
N2 - The representation of ENSO and NAO are examined in the Climate Forecast System, version 2 (CFSv2), reforecasts with a focus on the physical processes related to teleconnections and predictability. CFSv2 predicts ENSO well, but an eastward shift of the tropical Pacific sea surface temperature (SST) anomalies is evident. Although it appears minor on the global scale, the shift in convection and the large-scale wave train affects the model prediction of regional climate. In contrast, NAO is predicted poorly. The anomaly correlation coefficient (ACC) between the model ensemble mean and the observation is 0.27 during 1982-2010, and the ensemble spread is large. The representation of three sources of NAO predictability-SST, the stratospheric polar vortex, and the Arctic sea ice concentration-is investigated. It is found that the link between tropical Pacific SST and NAO is not well represented in CFSv2, and that the tropospheric- stratospheric interactions are too weak, both contributing to the poor prediction of NAO. Additionally, the impact of ENSO and NAO on prediction skill of CFSv2 in boreal winter is analyzed in terms of the spatial ACC of geopotential height. Active ENSO events exhibit larger prediction skill than neutral years, especially during the ENSO+/NAO2 and ENSO-/NAO+ winters. Spatial patterns of prediction skill are also examined, and larger skill of geopotential height and 2-m air temperature is found outlined by the nodes of the PNA pattern, consistent with the large signal-to-noise ratios associated with the ENSO teleconnection.
AB - The representation of ENSO and NAO are examined in the Climate Forecast System, version 2 (CFSv2), reforecasts with a focus on the physical processes related to teleconnections and predictability. CFSv2 predicts ENSO well, but an eastward shift of the tropical Pacific sea surface temperature (SST) anomalies is evident. Although it appears minor on the global scale, the shift in convection and the large-scale wave train affects the model prediction of regional climate. In contrast, NAO is predicted poorly. The anomaly correlation coefficient (ACC) between the model ensemble mean and the observation is 0.27 during 1982-2010, and the ensemble spread is large. The representation of three sources of NAO predictability-SST, the stratospheric polar vortex, and the Arctic sea ice concentration-is investigated. It is found that the link between tropical Pacific SST and NAO is not well represented in CFSv2, and that the tropospheric- stratospheric interactions are too weak, both contributing to the poor prediction of NAO. Additionally, the impact of ENSO and NAO on prediction skill of CFSv2 in boreal winter is analyzed in terms of the spatial ACC of geopotential height. Active ENSO events exhibit larger prediction skill than neutral years, especially during the ENSO+/NAO2 and ENSO-/NAO+ winters. Spatial patterns of prediction skill are also examined, and larger skill of geopotential height and 2-m air temperature is found outlined by the nodes of the PNA pattern, consistent with the large signal-to-noise ratios associated with the ENSO teleconnection.
KW - ENSO
KW - Forecast verification/skill
KW - North Atlantic Oscillation
KW - Seasonal forecasting
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U2 - 10.1175/JCLI-D-18-0389.1
DO - 10.1175/JCLI-D-18-0389.1
M3 - Article
AN - SCOPUS:85060981666
SN - 0894-8755
VL - 32
SP - 1307
EP - 1326
JO - Journal of Climate
JF - Journal of Climate
IS - 4
ER -