i-Box: Boundary Layer Measurement Platform in Very Complex Terrain

Planetary boundary layers in complex terrain remain one of the major challenges of today's boundary layer research both in terms of observational methodologies and high resolution numerical modeling. Especially lacking is a test bed for boundary layer processes in highly complex terrain. Information such a test bed can provide is crucial for filling in the gaps in the current knowledge and for providing a means of model verification in such a complex setting.

Within the project Innsbruck Box (or i-Box for short) such a test bed is presently being set up. It is designed to be a long-term “reference box” for studying the characteristics of turbulence structure and exchange processes in truly complex topography. i-Box represents an integrated approach combining three-dimensional long-term turbulence observations, in the vicinity of Innsbruck, with high-resolution numerical modeling. Both the observational data and results from numerical modeling will allow for improvements in process understanding, once the numerical models are capable of truly reproducing the observations. Numerical modeling will also be used to fill the data gaps in areas where no measurements are possible or the current measurement techniques are inadequate. Additionally, idealized numerical experiments will be performed in order to test hypotheses deduced from observations.

i-Box is located in the Inn Valley, an approximately Northeast-Southwest oriented valley in western Austria, characterized by very complex terrain with steep slopes, flat foothills, numerous side valleys, variable land use characteristics etc. i-Box sites are chosen as representative of the specific topographic features: valley bottom, slopes of different angles and orientation, in order to secure the universality of the obtained results.

This presentation will provide an outline of the i-Box approach, its set-up and prospective goals. Preliminary results from different characteristic sites will be presented, thus quantifying the heterogeneity in the surface fields. Due to the – in some cases – ‘extreme' character of local surface characteristics, a special emphasis will be placed on the estimation of uncertainties due to the choice of post-processing methods as compared to standard statistical uncertainty due to time averaging and heterogeneity. Some idealized high resolution numerical simulations will also be presented.