Physical processes driving intensification of future precipitation in the mid- to high latitudes: an example from Norway

Precipitation is changing as the climate warms. Downpours can potentially become more intense, frequent, and of longer duration due to the increased water holding capacity of the atmosphere and other (thermo)dynamical responses. However, the exact nature of the precipitation response and its characteristics are still not well understood due to the complex nature of the physical processes underlying the formation of clouds and precipitation. 

In this study, present and future Norwegian climate are simulated at convection-permitting scales with a regional climate model. Hourly precipitation is separated into three categories (convective, stratiform, and orographically enhanced stratiform). This is achieved using a physically-based algorithm that is tested over different mountainous areas. 

We investigate changes in the frequency, intensity and duration of precipitation events for each category, delivering a more nuanced insight into the precipitation response to a changing climate. Results show a significant intensification of autumn precipitation and more frequent convective precipitation. The precipitation response in autumn and spring deviates from the idealised thermodynamic response, partly owing to changes in cloud microphysics. These results show that changes in the precipitation distribution are affected in complex ways by the local climatology, terrain, seasonality and cloud processes. Given the societal impacts of intense rainfall, there is an imperative to further understand these complexities, thus enabling greater societal resilience to climate change.