Predicting Near-Surface Meteorological Variations over Different Vegetation Types

Meteorological conditions close to a surface are strongly influenced by the properties of the surface itself. As a result, input data for models calculating evaporation of surfaces differing from the measurement site need to be transformed. A transformation scheme proposed previously is tested on data from HAPEX-MOBILHY. Reference values of wind speed, temperature and absolute humidity at a height at which homogeneity is assumed over the landscape are estimated from observations over agricultural fields. From these reference values near surface conditions over a forest are computed. Wind, temperature and humidity differences between forest and agricultural fields are small in neutral atmospheric conditions but increase with increasing (un)stability. Correlations decrease with increasing distance between sites. The reference height, estimated by comparing the respective profiles from any pair of locations, varies with stability and differs between the three variables. Transformation via a fixed reference height introduces much noise but may be of some use to correct long term averages. Possible improvements are discussed