Studie der World Weather Attribution, 5.10.2022 (engl. Originalfassung)
In Europe, above-average air temperatures have been reported from the beginning of 2022, and spring — in the south also winter — was dry over most of the continent. In the subsequent 2022 summer, a sequence of heatwaves, combined with widespread precipitation shortages, fostered hot and dry conditions. The European 2022 summer was assessed “hottest on record” by the European Union’s environmental programme Copernicus, and was characterised by desiccating soils, particularly in Western regions (Copernicus, 2022), in the wake of the recent heatwaves. Based on runoff anomalies, it was also highlighted in the press in mid-August that the 2022 European drought could be the “worst in 500 years” (The Guardian, 13 Aug 2022).
But summer heat and drought were not restricted to Europe; e.g., Mainland China was ravaged by exceptionally high temperatures and aridity (BBC, 17 Sept 2022), and North America experienced an unusually warm summer (Copernicus, 2022). In the midlatitudes, extreme summer heat and precipitation shortages are typically fostered by persistent, often nearly- stationary anticyclones (e.g., Li et al., 2020), or subtropical ridges (e.g., Sousa et al., 2020), and many areas in Europe were subject to the strongest 500 hPa geopotential height anomalies since 1950, between May and July 2022 (Toreti et al., 2022). The strength and meandering of the extratropical jet stream can simultaneously promote hot and dry conditions as well as heavy precipitation in different regions (e.g., Lau & Kim, 2012), yet the understanding of the dynamics underlying such weather extremes and especially their associated future changes remains limited.
Nevertheless, to provide an example of the ongoing efforts and resulting discoveries, a recent study has suggested that many heatwaves in the ongoing century in Western Europe have been caused by a double-jet configuration, which is closely linked to anticyclonic flow and has increased in both frequency and persistence (Rousi et al., 2022). From a global perspective, ENSO has remained in the “La Niña” phase since late 2020 (WMO, 2022), which may have contributed to the hot and dry conditions in parts of both China and of North America (Wang et al., 2007, Karori et al., 2013).
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