RTI Act
Rain drop size distribution (DSD) was measured at four places in Southern India
{Thiruvananthapuram, Kochi, Munnar and Sriharikota (SHAR)} using a Joss-Waldvogel (JW) impact type disdrometer. The data for each minute were corrected for dead time errors and rain rate was computed from the corrected data. The data for a whole month were then sorted according to rain rate (R) into several classes ranging from 0.1 to >100 mm/h.
The average DSD in each class was computed, and the lognormal distribution function was fitted to the average. The fit parameters were found to have dependence on rain rate. The total number of drops (NT), the geometric mean diameter (Dg) and the standard geometric deviation (a) were also computed from the fit parameters. The standard geometric deviation (a) was found to be more or less constant with rain rate at all the sites and in all months. The other two, parameters (NT and Dg) were found to vary exponentially with rain rate except in Munnar, a high altitude station. At Thiruvananthapuram, in most of the months, NT increased exponentially with rain rate up to some value of rain rate, which was different in different months, and then remained more or less constant or decrease slightly.
Details can be found at – R. Harikumar et al,”Variation of rain drop size distribution with rain rate at a few coastal and high altitude stations in southern peninsular India”, Advances in Space Research (2009), doi:10.1016/j.asr.2009.09.018
