ECMWF-S4 assessment of monthly weather regimes against ERA-Interim
Assessment of monthly weather regimes (NAO+, NAO-, Atlantic ridge and Blocking) of the prediction system System 4 from the European Centre for Medium-Range Weather Forecasts (ECMWF) against the ERA-Interim reanalysis for the period 1981-2015. Figures are organized in five different groups, one for each type of comparison between predicted and observed data: between monthly weather regime anomalies (first group), between interannual frequencies (second group), between the impact on 2m temperature (third group) and between the impact on 10m wind speed (fourth group). Each composition inside a group represents a single target month and different previous start dates (up to six months in advance). Last column to the right of each figure shows the observed values for each regime.
Fifth group of figures is a collection of different metrics: the spatial (pattern) correlation between simulated and observed regime anomalies (figures in the first group), the temporal correlation between sim. and obs. interannual regime frequencies (figures in the second group), spatial correlation between the sim. and obs. regime impact on 10m wind speed and 2m temperature, bias of the average regime frequency 1981-2015 (third image at bottom), bias of the regime persistence, transition probability bias (one composition for each regime). Finally, three figures are shown. First composition illustrates the monthly ERA-Interim regime anomalies measured by means of a 3-months running k-means clustering. The second one is similar to the first, without the 3-months running clustering. Third and last figure shows the Taylor diagram of the observed monthly regime anomalies, as compared to the observed DJF regime anomalies, for both the k-means clustering and the 3-months running clustering.
For more information, see Scientific Technical Note Cortesi et al. (2016b).