STINHO—structure of turbulent transport under inhomogeneous surface conditions—comparisons of flux measurements with horizontal-stretched observations

A micrometeorological field experiment within the scope of the STINHO-project (STructure of turbulent transport under INHOmogeneous conditions) was performed at the boundary layer research field of the Meteorological Observatory in Lindenberg (German Weather Service) in the summer of 2002. The aim of this examination was to investigate the interaction of an inhomogeneously heated surface with the turbulent atmosphere. To observe spatially and temporally variable flow and temperature fields above a heterogeneous land surface, acoustic methods (travel time tomography) and optical observation methods (infrared-camera or line-integrated scintillometer-measurements) were used.

Due to the combination of the experimental and theoretical studies the STINHO project is focussed on the following tasks: 1) to prepare a data set to initialise a Large-Eddy Simulation (LES) model, 2) to compare LES output with observations especially concentrating on non-homogeneous heating conditions and 3) to check the representativeness of meteorological point measurements in a heterogeneous landscape.

The current set-up of the measurement and analysis technique can provide an image of land surface/atmosphere interaction parameters and processes which corresponds with the grid structure of LES models. The data-set can therefore directly used for the initialisation and validation of the numerical model.

The combination of area-wide tomography and infrared-camera temperature observations were used to calculate a bulk parameterisation of the amount of the vertical sensible heat flux above different land use types. The comparison of the spatial and temporal variability of the turbulent heat fluxes with direct measurements (e.g. eddy-covariance) shows in principle an good agreement between the different methods.

The results of the STINHO investigations were used to estimate how horizontal flux divergences induced by heterogeneous surfaces modify the vertical turbulent fluxes. These investigations lead to a better understanding of the energy exchange above micro-scale heterogeneous surfaces.