Estimation of Raindrop Size Distribution over Darjeeling (India)

Abstract:

A study of rain drop size distribution (DSD) model over Darjeeling (27⁰01^’N, 88⁰15^’E), India, have been carried out using a Micro Rain Radar (MRR) on the basis of MRR which measures DSD (number of rain drop size and rain rates with the time interval of one minute), at the particular heights and the different rain rates. Applying the DSD model of exponential, lognormal, and gamma, to check the true estimation of drop size distributions and it has been estimated by the lower order moments and higher order moments for gamma Distributions. It shows the DSD at different altitudes from 150 m to 2000 m, in the vertical steps of 500 m. however it has been simulated the DSD data about 2 km out of 4.5 km. (I). At the height of 150 m where most of DSD behaves in accordance to gamma Distributions according to the moments order of low and the moments order of high, However, where occupying low concentrations for any rain rates, (ii). Upper altitudes from 450 m to 2000 m as where as shown most of DSD behaves gamma Distributions according to the moments order of high only, However, where occupying high concentrations for any rain rates. DSD at the altitudes of 2 km and even more 4.5 km (as not shown) but every height behaves more or less similar manner except at the height of 150 m, The DSD of empirical model has been derived on the basis of fit parameters evaluated from experimental data. It is observed that data fits well in gamma distribution for Darjeeling. And relation between slope (Ʌ) and shape (µ) which bears the best resemblance at the height of 150m (ground surface) at the lower order moments by the linear fit for any rain rates. In higher altitudes obtained where shape (µ) and slope (Ʌ) which is not making any resemblance by the linear fit or polynomial fit for any rain rates in Darjeeling.