MIXING HEIGHT ESTIMATION FROM SODAR DATA - A CRITICAL DISCUSSION

Sodar measurements have been used to estimate the mixing height for ab out 20 yr, nevertheless the issue is still the subject of controversia l discussion. The paper attempts to critically examine the methods and results of mixing height determination from sodar data that have been reported in the literature. The theoretical base, the methods suggest ed, the automatization of algorithms, and the intercomparison of sodar -based mixing height values with data from independent measurements an d models are briefly discussed. An assessment is given of sodar capabi lities in comparison with other profiling techniques. It is concluded that sodar data may be used to derive reliable mixing height informati on in many situations which are of special relevance for environmental monitoring, namely in stagnant weather situations with low mixing hei ght values between about 50 and 500-1000 m, depending on the type of t he sodar. However, the algorithms available up to now for their automa tic evaluation appear not yet reliable enough to be recommended for op erational purposes, and a control of the output by a trained analyst i s advisable. Simultaneous operation of sodars and other remote sensing systems (lidar, wind profiler) is shown to be a promising way to over come the range limitations of sodars and to allow continuous mixing he ight estimation throughout the complete diurnal cycle. (C) 1997 Elsevi er Science Ltd.