naclim ct1-3 meeting, at mpi, 19-20/03/2014 on the predictability of the winter north atlantic...
TRANSCRIPT
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
On the predictability of the winter North Atlantic Oscillation: lagged influence of autumn Arctic sea-ice and Eurasian
snow
J. García-Serrano, C. Frankignoul
LOCEAN-IPSL, Paris, France
with contributions from: G. Gastineau (LOCEAN-IPSL) and A. de la Cámara (LMD-IPSL)
further explore the covariability by means of describing the spatial patterns and the associated dynamics; two key elements for assessing
model reproducibility and performing sensitivity experiments
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
On the predictability of the winter North Atlantic Oscillation: lagged influence of autumn Arctic sea-ice and Eurasian
snow
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
extended-MCA (EMCA)
weekly snow cover extent in October (40th-44th)
(Cohen and Jones 2011)
correlation skill for cross-validated hindcasts 1979/80–2012/13
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
correlation skill for cross-validated hindcasts 1979/80–2012/13
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
upward-propagating wave activity
(stratospheric mechanism)
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
upward-propagating wave activity
(stratospheric mechanism)
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
transient-eddy feedback
(tropospheric mechanism)
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
Summary:
• September Arctic sea-ice variability (MCA-SIC), in particular over the Barents-Kara Seas, is associated with a wave-like anomaly crossing Eurasia in November that (i) impacts vertical wave activity over both the North Pacific and northern European sectors, thus modulating the stratospheric vortex strength; and (ii) induces a positive transient-eddy feedback over the eastern North Atlantic helping to maintain the tropospheric anomaly. Negative SIC anomalies (i.e. sea-ice reduction) over the Barents-Kara Seas are followed by a negative NAO phase in winter.
• Time-evolving October Eurasian snow variability (EMCA-SCE) shows a south-westward progression from eastern to central Siberia, with larger SCE anomalies preceding a negative NAO phase in winter. This time-evolving SCE pattern leads to changes in the Siberian High, which further lead to enhanced/reduced vertical wave activity over eastern Eurasia affecting the stratospheric polar vortex over the North Pacific sector.
• These observational, surface-boundary forcings (Arctic SIC; Eurasian SCE) can be used to formulate empirical predictions of the winter NAO index (>50%) and European surface climate, as benchmark for dynamical predictions.
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
J. García-Serrano and C. Frankignoul (2014) - Nature Geoscience, 7, 10.1038/NGEO2118
J. García-Serrano, C. Frankignoul, G. Gastineau, A. de la Cámara (2014) - J. Climate (almost-submitted)
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299 (NACLIM – www.naclim.eu)
NACLIM CT1-3 meeting, at MPI, 19-20/03/2014
EXTRA SLIDES
wave-like anomaly preceding the
establishment of the winter NAO
vortex split preceding the
establishment of the winter NAO
vortex splits are followed by negative NAO-like at surface
(Mitchell et al. 2013, JCLIM)
wave-like anomaly precedes NAO-like
(Kuroda & Kodera 1999, GRL)
leading to enhanced vertical propagation
of wave actvity
(Garfinkel et al. 2010, CDYN)
upward-propagating wave activity (stratospheric pathway)
transient-eddy feedback
(tropospheric mechanism)
LEFE workshop, at LOCEAN, 05/12/2013
Honda et al. (2009, GRL)
SIC (oct) SIC (nov)
The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013), under grant agreement n.308299NACLIM www.naclim.eu