Complex terrain refers to areas with rugged or irregular topography, such as mountains, valleys, and cliffs. This type of terrain can have a significant impact on atmospheric processes, such as wind patterns and precipitation, as well as on the dispersion of pollutants and the transport of airborne particles. Researchers in this area study the interactions between the atmosphere and the underlying terrain, as well as the effects of complex terrain on weather patterns and climate. Understanding complex terrain is important for a variety of applications, including weather forecasting, air quality management, and infrastructure design.