Concept and first results of an airship-borne cloud turbulence system

There are still gaps and uncertainties in our knowledge of climate forcing by clouds and aerosols. The aim of a European project (EUROZEP) is therefore the airbship-borne investigation of dynamical, microphysical and radiative properties in and above stratiform clouds. For a better understanding of these processes controlling the microphysic and the radiative properties of clouds the study of cloud top entrainment is required. Turbulent mixing of cloud free air into clouds is supposed to take place on very small scales in stratiform cloud sheets. Because there are some severe uncertainties in certifying the prototype Zeppelin NT (New Technology) first tests of the platform system have to be carried out at a coastal site in Northern Germany in Spring 2000 using a 400 m3-tethered ballon of the German Army. There is a good chance of fog and low marine stratus at this site. The maximal payload of the turbulence platform (150 kg) will include the sonic anemometer, a new ultrafast thermometer with a special drop protection (developped in cooperation with the University of Warsaw/Poland), a Particulate Volume Monitor, a Lyman-alpha-hygrometer, and DGPS and inertial sensors. Assuming a typical wind speed of 10 m/s and a sampling rate of 100 Hz a spatial resolution of 10 cm should be possible. Detailed investigations of the ultrasonic anemometer used will be given by Siebert and Muschinski (see abstract). A technical description and first experiences with the whole platform will be presented here.