Interactions between the extratropical
ocean and the atmosphere on seasonal to multidecadal time scales
- by Claude Frankignoul
Claude Frankignoul current research
interest includes understanding the interactions between the
extratropical ocean and the atmosphere on seasonal to multidecadal
time scales.
Particular attention has been given
to detecting the influence of midlatitude SST anomalies on the atmosphere.
Czaja and Frankignoul (1999, 2002, see also Frankignoul and Kestenare
2005) showed that a midlatitude horseshoe SST anomaly pattern has
a significant influence on the North Atlantic Oscillation in early
winter.Recently, an influence of North Pacific SST anomalies on the
atmospheric circulation was found in late summer and early winter
(see figure below) in Frankignoul and Sennéchael (2007).
The feedback between SST anomalies and the surface heat
flux has been studied in observations and coupled models (e.g. Frankignoul
et al. 2004).
The link between the Gulf Stream
variability and the atmosphere has been studied using observations
(Frankignoul et al. 2001) and ocean GCM simulations (de Coëtlogon
et al 2006). The relation with the changes of the North Atlantic circulation
are being investigated in a recent hindcast with a higher resolution
ocean model.
Figure 1. Maximum covariance pattern for the geopotential
height in November, December and January (contour interval 6 m with
negative values dashed) and SST (color) anomalies between lag –4
(SST leads) and lag 1 (SST follows). The analysis is based on monthly
anomaly data from the NCEP reanalysis. The time series have been
normalized so that the figure shows typical amplitudes. The correlation
C between the MCA time series, the square covariance (SC) fraction
F, and the SC are given for each lag. The estimated significance
levels are given in parentheses. |
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