Understanding the Boundary Layer Structure and Exchange Processes over Complex Mountainous Terrain: Is there a Chance of Success for a Project like i-Box?

The ‘Innsbruck-Box' (i-Box) project combines multi-site, long-term observational efforts in truly complex, mountainous terrain with high-resolution numerical modeling in order to understand flow and turbulence characteristics in mountainous boundary layers and the exchange to the free troposphere over this type of terrain. Clearly, this is an ambitious endeavor since the current description of mountainous boundary layers suffers from a need to violate all fundamental assumptions of classical boundary layer theory (maybe with the exception of stationarity, which is not necessarily a larger problem than over flat terrain). While horizontal inhomogeneity is intrinsic to mountainous terrain due to radiative and dynamic effects, non-flat surfaces trigger all sorts of additional difficulties – starting from some of the basic definitions and ranging to observational and computational difficulties. Moreover, rough to very rough surfaces are the rule rather than the exception in truly mountainous terrain, which in turn covers substantial parts of the land-surface worldwide. In this contribution we discuss these fundamental obstacles, formulate a number of pre-requisites for how to possibly overcome these and present some examples for why we think there is a clear ‘yes' to the title-question.