Thermally induced wind systems, such as the diurnal slope and valley winds, are

an important component of the boundary layer over mountainous regions with a

large influence on mountain weather and climate. In current numerical weather

prediction models these winds are often poorly resolved, also their role in

land-atmosphere exchange over complex terrain is unclear. A recent evaluation of

the representation of the valley winds in the Alpine region in the NWP model

COSMO will be discussed, as well as an investigation of heat exchange processes

over complex terrain by means of large-eddy simulation in order to bring light

into the current debate on the valley heating mechanisms.