Afforestation reduces cyclone intensity and precipitation extremes over Europe

Extratropical cyclones are the dominant weather pattern in the midlatitudes and cause up to 80% of precipitation extremes in some regions of Europe with a large societal and economical impact. Using a regional climate model and a cyclone-tracking algorithm, we study how idealized deforestation and afforestation of Europe affect long-term changes in the number and intensity of cyclones, and their effects on precipitation. The number of cyclones over Europe is smaller for afforestation compared to deforestation, with differences starting from 10% in regions near the west European coast and increasing towards the east to reach 80%. This decrease is caused by the larger surface roughness in afforestation. The winter precipitation extremes are considerably reduced with afforestation, without a large decrease in mean precipitation because of the balancing effect of increased weak and moderate precipitation. The mean precipitation increases over central and southern Europe as a result of the summer precipitation increase caused by larger evapotranspiration and access to deeper soil moisture in the presence of trees. These different region-specific effects of afforestation are generally positive and could provide an important mitigation tool in a changing climate.