Small scale turbulence and instabilities observed simultaneously by radiosondes and the MU radar
Résumé
A Japanese-French field campaign devoted to the study of turbulence and instabilities in the troposphere and lower stratosphere was conducted in September 2011 for three weeks at the Shigaraki MU observatory (Japan). During the experiment, 59 radiosondes (Vaisala RS92G) were successfully launched and MU radar/lidar measurements were performed. The detection of turbulence from the in situ profiles is based on a Thorpe analysis. We have developed an original method for selecting the "true" turbulent events within the profile, i.e for rejecting the events induced by instrumental noise. The method is based on both an optimal noise reduction and a statistical hypothesis test. From the raw data of radiosoundings (3-6 m vertical resolution), we detected those turbulent regions whose vertical extent is larger than ~ 40 m in the troposphere, ~15 m in the lower stratosphere. By taking into account the water vapor saturation effects, we also detected (conditional) static instabilities within the clouds. In addition, the MU radar measurements were acquired in range imaging (FII) mode, allowing to observe turbulence and KH instabilities with an exceptional time-space resolution (~ several 10 m, 20 s). We shall present the very first results of this campaign including direct comparisons of turbulent events observed simultaneously by radiosondes and MU radar.
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