DJF Weather regimes

Upper panel: DJF weather regimes from NCEP SLP (reference period 1970-2010). The isolines are SLP anomalies for each centroid.

• Regime 1 is NAO-,
• Regime 2 is Atlantic RIDGE,
• Regime 3 is SCANDINAVIAN BLOCKING,
• Regime 4 is ZONAL (or NAO+).

Middle panel:  daily classification since the first day of the running (or last) winter season (vertical bars). The classification is done by minimizing the rms between the observed anomaly and the weather regimes in the upper panel. The diameter of circles indicate the spatial correlation with the four weather regimes (only positive correlations are shown). Note that minimizing an rms is not equivalent to maximizing the correlation.

Lower panel:  statistics of frequencies (percentage of occurrences during the season) for the four regimes since 1948. A png file can be obtained by clicking on the figure.

The complete classification file is available here. The files are updated every mondays.