Over complex terrain, spatial inhomogeneities of pre-convective atmospheric conditions occur due to convection and mesoscale transport processes. This thesis focuses on the identification of these processes over the mountainous island of Corsica and on the evaluation of their impact on the spatial variability of water vapour, convection-related parameters and the evolution of deep convection by means of observations.

Strong winds accompanying extratropical cyclones are commonly associated with various mesoscale features. This work introduces RAMEFI (RAndom-forest-based Mesoscale wind Feature Identification), an objective and flexible identification approach based on key surface characteristics to distinguish these features. RAMEFI is further applied to compile a climatology over Europe, offering a comprehensive analysis of feature frequency, distribution, and characteristics.

Two aspects of anthropogenic impacts on the atmosphere are investigated using means of numerical weather prediction. A case study is conducted to estimate the impact of such artificial clouds on the incoming solar radiation at the Earth's surface with special regard to photovoltaic power production. Furthermore, simulations are performed to assess the efficacy of injecting particles into the Arctic troposphere with the aim of modifying cirrus clouds for counteracting global warming.

The impact of land-surface properties like vegetation, soil type, soil moisture, and the orography on the atmosphere is manifold. These features determine the evolution of the atmospheric boundary layer, convective conditions, cloud evolution and precipitation. The impact of model grid spacing and land-surface resolution on convective precipitation over heterogeneous surfaces is investigated using ICOsahedral Nonhydrostatic (ICON) simulations within the framework of the HD(CP)2 project.

Warm conveyor belts (WCBs) are weather systems that substantially modulate the large-scale extratropical circulation. As they can amplify forecast errors and project them onto the Rossby wave pattern, they are of high relevance for numerical weather prediction. This work elaborates on two aspects of WCBs in the context of ensemble forecasts: (1) sensitivities of WCBs to the representation of initial condition and model uncertainties, and (2) the role of WCBs for forecast error growth.

By using COSMO-ART, highly resolved process study simulations for 2-3 July 2016 are conducted to assess the aerosol effect on the meteorological conditions of southern West Africa. The meteorological phenomenon Evening Monsoon Flow Enhancement (EMFE) is identified as highly susceptible to the aerosol direct effect, leading to a spatial shift of the EMFE front. In a second aerosol feedback chain the aerosol variation leads to a temporal shift of the stratus-to-cumulus transition.