Synoptic circulation changes over Central Europe from 1900 to 2100: Reanalyses and Coupled Model Intercomparison Project phase 6

Abstract

While the evidence for anthropogenic climate change continues to strengthen, and concerns about severe weather events are increasing, global projections of regional climate change are still uncertain due to model‐dependent changes in large‐scale atmospheric circulation, including over North Atlantic and Europe. Here, the Jenkinson–Collison classification of daily circulation patterns is used to evaluate past and future changes in their seasonal frequencies over Central Europe for the 1900–2100 period. Three reanalyses and eight global climate models from the Coupled Model Intercomparison Project phase 6, were used based on daily mean sea‐level pressure data. Best agreement in deriving relative frequencies of the synoptic types was found between the reanalyses. Global models can generally capture the interannual variability of circulation patterns and their climatological state, especially for the less frequent synoptic types. Based on historical data and the shared socioeconomic pathway 5 scenario, the evaluated trends show more robust signals during summer, given their lesser internal variability. Increasing frequencies were found for circulation types characterized by weak pressure gradients, mainly at the expense of decreasing frequencies of westerlies. Our findings indicate that given a high‐emission scenario, these signals will likely emerge from past climate variability towards the mid‐21st century for most altered circulation patterns.

On the representation of atmospheric circulation modes in regional climate models over Western Europe

“…A similar result was reported by Herrara‐Lormendez et al . (2022) that in Europe, there is a better agreement in the representation of synoptic circulations among reanalysis products compared to GCMs. Also, Table A3 and Figure A1 show that the explained variance of the analysed components from ERA5 and the climate models are quite close and comparable across the RCMs driven by a given data.…”

“…The classification of atmospheric circulation modes, using climate simulations, commonly employs GCMs (e.g., Huth, 2000; Sheridan and Lee, 2010; Ibebuchi, 2022a). Studies have identified that GCMs are capable to simulate the large‐scale atmospheric circulation modes as observed, though with biases (Cannon, 2020; Herrara‐Lormendez et al ., 2022; Ibebuchi, 2022a), such as lack of blocking in the North Atlantic sector and misrepresentation of the North Atlantic westerlies (Simpson et al ., 2020). The aforementioned circulation biases are regional constraints in studying and projecting changes in dynamically downscaled surface variables such as precipitation (e.g., Zhang and Soden, 2019; Fernandez‐Granja et al ., 2021).…”

Forecasting extreme precipitation in the central Mediterranean: Changes in predictors' strength with prediction lead time

“…Tools for addressing causal relationships can be used for this task (Di Capua et al, 2020;Silini & Masoller, 2021). Finally, it would be useful to assess if the ongoing climate change could impact the frequency of the Mediterranean patterns, something that is already demonstrated for the large-scale variability over other parts of the world (Herrera-Lormendez et al, 2022;Pope et al, 2022).…”

Projected changes in synoptic circulations over Europe and their implications for summer precipitation: A CMIP6 perspective

“…The eighth most common pattern during summer is the easterly (E). Its occurrence, for example, over central Europe, is often associated with a dominant anticyclone over northern Europe; at times linked with heatwave events, dry days, and the advection of hot air from the inner continent (Herrera-Lormendez et al, 2021). The remaining circulation types (SW, S and SE) account for the remaining 12% of the variability.…”

“…These limitations are due to the classification's dependency on the marked meridional and zonal pressure gradients that determine the structure and movement of these synoptic surface patterns. Applications from the JCC largely suggest future summer weakening in meridional pressure gradients, directly triggering changes in the average synoptic conditions in Europe—more similar to conditions in the Mediterranean and the south of Europe after the mid‐21st century (Herrera‐Lormendez et al, 2021). This tendency also suggests seasonal changes in the mean zonal state of synoptic circulations like the westerlies and easterlies as well as cyclones directly influencing regional precipitation changes, for example, over the British Isles (Burt & Ferranti, 2012).…”