Raindrop axis ratios, fall velocities and size distribution over Sumatra from 2D-Video Disdrometer measurement

• Published in: Atmospheric research 2013-01, Vol.119, p.23-37
• Main Authors: Marzuki, Randeu, Walter L., Kozu, Toshiaki, Shimomai, Toyoshi, Hashiguchi, Hiroyuki, Schönhuber, Michael
• Format: Article
• Language: English
• Subjects: Axis ratio; Disdrometer; Falling velocity; Kototabang; Raindrop size distribution
• ISSN: 0169-8095; 1873-2895
• DOI: 10.1016/j.atmosres.2011.08.006

Raindrop axis ratio, falling velocity and size distribution are important in broad list of applications. However, they are not frequently observed in the equatorial region. This paper elucidated the characteristics of raindrop axis ratio, falling velocity and size distribution based on 2D-Video Disdrometer (2DVD) data that have been collected in the equatorial Indonesia, particularly at Kototabang (hereafter called KT), west Sumatra, Indonesia (0.20°S, 100.32°E, 864m above sea level). A comprehensive follow-up of the previous study on the natural variability of raindrop size distributions (DSDs) is presented. Precipitation was classified through 1.3-GHz wind profiler observation. The dependence of raindrop falling velocity and axis ratio on rainfall type was not clearly observed. Overall, measured raindrop fall velocities were in good agreement with Gunn–Kinzer's data. Raindrop axis ratio at KT was more spherical than that of artificial rain and equilibrium model, and close to the values reported in the turbulent high shear zone of surface layer which can be partially due to the effect of the instrument errors (e.g., location and container shape). Of some natural variations of DSD investigated, the dependence of DSD on rainfall rate and rainfall type as well as diurnal variation was clearly visible. A striking contrast between the stratiform and convective rains is that the size distributions from the stratiform (convective) rains tend to narrow (broaden) with increasing rainfall rates. For rainfall rate R