After the comparison measurements of three Solent-Gill ultrasonic anemometers (Types Standard, Enhanced, Research) at the top level (34 m) of the BASTA-tower from August 16th to September 27th in 1995 the Research-Sonic has been dismounted and the Enhanced-Sonic has been mounted on a lower level (28 m). The temperature fluctuations are measured with thermocouples (75 m). With this the turbulent fluxes of momentum and heat are now measured continuously as halfhourly mean values in addition to the profile measurements of wind, temperature and humidity.
First results of the comparison measurements have been presented at the EGS (European Geophysical Society) workshop '95 in Hamburg (Vogt et al., 1995). The flow conditions at the BASTA-tower have been analysed by Gempeler (1995).
Based on the landuse-classification derived from Landsat-TM and ERS-1 data the roughness length z0 was calculated for the region of Basel and a map with roughness information has been established. This work was presented at the 15th symposium of EARSeL (European Association of Remote Sensing Laboratories) 1995 in Basel (Scherer et al., 1995). The results of this research shall be included in future analyses and be compared with ground measurements.
In 1995 the essential work within the SNF-project 20-40621.94 consisted in the planning and execution of a special measurement campaign on the roof of the Messe Basel from July 1995 to the end of February 1996. Fig. 1 shows the location of the antenna-tower. Due to the height (76 m above street level) of this tower the probing of the urban boundary layer can be extended to higher levels compared to the BASTA-tower. This allows a more precise analysis of the vertical structure of the turbulent characteristics in the roughness-sublayer.
Three ultrasonic anemometer-thermometers measured at three heights the fluctuations of the wind vector and the accoustic temperature (u', v', w', v'). The data were sampled at 21 Hz and all raw data were stored for subsequent analysis. Additionally two profiles of wind speed (u), and one profile of air temperature () and humidity (q) were measured. Each profile consisted of six heights. Wind direction () was determined at three levels, and net radiation (Rn) was measured at 64 m. The profile data were stored as 10 min averages. Fig. 2 and Tab. 1 give an overview on the site and the instrumentation of the antenna-tower.
From July 17th to September 13th 1995 a SODAR (Type RemTech PA1) supplied by the Institut für Physische Geographie of the University of Freiburg i.Br., Germany, was installed and operated on the roof of a parking lot 30 m above street level and about 200 m south of the antenna tower (see also Fig. 1).
To verify the data of the special measurement campaign the applied sonics have been recalibrated in the wind tunnel of Federal Institute of Technologies in Zurich in March 1996. This happened within a comparison of ultrasonic-anemometers from five different manufacturers (Solent-Gill, Campbell, Kajo-Denki, Metek, ATI). An extensive investigation of the accuracy of Sonic anemometers can be found in Vogt (1995). The results of this work are the basis for the wind channel experiments. All sensors for wind, temperature and humidity from the antenna-tower have been compared to each other during the RESMEDES (REmote Sensing of MEditerrean Desertification processes and Environmental Stability) field campaign in spring 1996.
The remaining time will be reserved to analyse the large amount of data, to write a dissertation and to prepare publications and speaches.
First results have been presented at the ICUC '96 (International Conference on Urban Climatology) in Essen (Feigenwinter et al., 1996; Vogt and Feigenwinter, 1996). Also at this conference the analyses referring to the spatial distribution of the properties of urban surfaces based on remote sensing and GIS data have been presented (Scherer et al., 1996; Beha et al., 1996; Parlow, 1996).