Abstract
Abstract. The efficacy of Euro-Atlantic circulation regimes for estimating wintertime climate anomalies (precipitation and surface temperature) over Europe is assessed. A comparison of seasonal climate reconstructions from two different regime frameworks (cluster analysis of the low-level zonal flow, and traditional blocking indices) is presented and contrasted with seasonal reconstructions using the North Atlantic Oscillation (NAO) index. The reconstructions are quantitatively evaluated using correlations and the coefficient of efficiency, accounting for misfit in phase and amplitude. The skill of the various classifications in reconstructing seasonal anomalies depends on the variable and region of interest. The jet and blocking regimes are found to capture more spatial structure in seasonal precipitation anomalies over Europe than the NAO, with the jet framework showing generally better skill relative to the blocking indices. The reconstructions of temperature anomalies have lower skill than those for precipitation, with the best results for temperature obtained by the NAO for high-latitude and by the blocking framework for southern Europe. All methods underestimate the magnitude of seasonal anomalies due to the large variability in precipitation and temperature within each classification pattern.
Highlights
Seasonal precipitation and temperature anomalies over Europe exhibit large year-to-year variability, with direct societal impacts such as on crop yields and renewable energy production (Grams et al, 2017; Jerez et al, 2013; Lesk et al., 2016)
Temperature, and precipitation anomalies are associated with each North Atlantic Oscillation (NAO) phase, blocking category, and jet cluster (Figs. 2–4)
The panels are arranged such that each row includes “similar” patterns identified using the NAO index, blocking, and the jet clusters
Summary
Seasonal precipitation and temperature anomalies over Europe exhibit large year-to-year variability, with direct societal impacts such as on crop yields and renewable energy production (Grams et al, 2017; Jerez et al, 2013; Lesk et al., 2016). Pfahl and Wernli, 2012; Sillmann and Croci-Maspoli, 2009; Trigo et al, 2004), and the configuration of the North Atlantic jet stream (Woollings et al, 2010; Madonna et al, 2017). All these complementary classifications have been shown to be able to capture specific aspects of the wintertime climate over Europe, but there has been to our knowledge no direct comparison of the skill of these classifications in reconstructing seasonal climate
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