The development of clouds has many causes, not all of those are examined. In consideration of rainfall behaviour and distribution knowledge of cloud formation, processes in the tropics are of particular importance. Clouds are part of the hydrological cycle, influencing water resources and the energy budget. The insight into unknown cloud generation processes is a great benefit in the developmental procedure of understanding the structure and functionality of an ecosystem and its biodiversity.

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... e main objective of the presented study was to investigate an unidentified nocturnal cloud formation procedure in the eastern Andes of South Ecuador and the adjacent northern Peruvian Amazon. The central theses encompass the confluence of katabatic flows in highly complex terrain due to a concave configuration. This cold drainage of air induces a surface cold front in the foothills of the eastern Andes, which initiates moisture convection due to compressional lifting by the terrain; a nocturnal LLJ triggers the development of the MCS. For the evaluation of the hypotheses the numerical model ARPS was used to analyse the not fully understood highland - lowland interactions in the PBL. At first, simulations of an accurate katabatic flow and its behaviour in complex terrain were performed with optimal conditions and without location information. The main subject of the study was the confluence of the cold drainage of air as a result of concave-lined terrain. Simplified DEMs, inspired by the Andes, were used for this analysis, due to the very steep slopes and valleys of the real terrain. A stepwise increase in their complexity, beginning with a simple slope, enabled the examination of the impact of the terrain configuration on the flow's dynamic behaviour. With the most complex terrain model, which represents a concave ridgeline interrupte [...]