Drop Shape Studies in Rain Using 2d Video Disdrometer and Polarimetric, Dual-wavelength Radar

Rain drop shapes play an important role in algorithm development for determining rainfall rates from polarimetric radar measurements [1]. It has been shown previously that the 2D video disdrometer (2DVD) [2] is capable of providing accurate information on drop shapes. An artificial rain experiment conducted under calm wind conditions [3, 4] yielded the mean drop shapes and the shape variations due to drop oscillations after a fall of 80 m. Later, the mean shapes as well as the axis ratio distributions were compared with wind-tunnel measurements and were shown to be in good agreement [5]. 2DVD measurements in natural rain have also been made, and very recently, one event study [6] in Alabama, USA, has indicated that drop shapes can at times vary somewhat from the aforementioned mean shapes. This was verified using polarimetric radar measurements at C-band made over the 2DVD site. In this paper, we present another event study from another location, namely, South-East Queensland near Brisbane, Australia, where a well calibrated 2DVD was recently installed at a location which not only has polarimetric radar coverage but also dual-wavelength radar observations at S and X bands.