Large-eddy simulations with strong lateral forcing representative of precipitation over the Netherlands are performed to investigate the influence of stability, relative humidity (RH), and moisture convergence on precipitation. Furthermore, a simple climate perturbation is applied to analyze the precipitation response to increasing temperatures. Precipitation is decomposed to distinguish between processes affecting the precipitating area and the precipitation intensity. It is shown that amplification of the moisture convergence and destabilization of the atmosphere both lead to an increase in precipitation, but on account of different effects: atmospheric stability mainly influences the precipitation intensity, whereas the moisture convergence mainly controls the precipitation area fraction. Extreme precipitation intensities show qualitatively similar sensitivities to atmospheric stability and moisture convergence. Precipitation increases with RH due to an increase in area fraction, despite a decrease in intensity. The precipitation response to the climate perturbation shows a stronger response for the precipitation intensity than the overall precipitation, with no clear dependency on changes in atmospheric stability, moisture convergence, and relative humidity.

Research on relations between atmospheric conditions and extreme precipitation is important to understand and model present-day climate extremes and assess how precipitation extremes might evolve in a future climate. Here we present a statistical analysis of the relation between large-scale conditions and hourly precipitation at midlatitudes, by using observations of the Netherlands combined with a regional reanalysis. The aim is to gain a better understanding of the typical large-scale atmospheric conditions and large-scale forcing associated with extreme hourly precipitation and determine the typical differences between cases of extreme precipitation and weaker events. To avoid double counting, we perform an event-based analysis and consider the hourly peak intensity, rather than all hourly data. Atmospheric large-scale profiles consistently show a clear separation between precipitation deciles, characterized by increasing instability and moisture content of the atmosphere for more extreme precipitation. Furthermore, stronger events are characterized by larger atmospheric forcing preceding the event, which primarily relates to vertical motions. Based on these results, four atmospheric parameters, describing atmospheric moisture, stability and large-scale convergence, are analyzed as potential indicators of strong precipitation events. Despite positive relations between these parameters and the peak intensity, their correlations are found to be weak.