Climate Change Impacts on Severe Thunderstorms in Finland

This study provides an estimate of the possible changes in frequency and intensity of severe thunderstorms in Finland under one of the projected future climate scenario. Our tool for this study is the high-resolution (25 km) regional atmospheric model (RCA3) developed by the Rossby Centre. The model runs follow the SRES A1B emission scenario. Two 30-year time periods were analyzed: a 30-year control run describing the present climate conditions (1971–2000) and a scenario run corresponding to 2071–2100.

The tornado and large hail observations are compared to the outputs of the control run to define severe weather probabilities within specific storm environments. We use the convective available potential energy (CAPE) and vertical wind shear as the quantitative measures characterizing the storm environment. The environmental thresholds for delineating severe thunderstorm occurrence are derived from the values of CAPE and wind shear in the present climate. The probability of any severe weather, large hail or tornado events in specific storm environments in the current climate as well as the changes in their frequency and intensity under the projected future climate conditions are analyzed.