2.4. Hydrometeor identification
A hydrometeor identification (HID) algorithm by Dolan et al. (2013) is used to identify types of hydrometeors present at different heights within a convective system. This is a fuzzy logic-based algorithm in which a fuzzy logic score (μ) is calculated (Equation 2) for each hydrometeor type and the hydrometeor with the highest fuzzy logic score is the most probable hydrometeor type at that grid point within the radar scan volume.
\begin{equation} \mu_{i}=\left[\frac{W_{Z_{\text{dr}}}\beta_{Z_{\text{dr}},i}+\ W_{K_{\text{dp}}}\beta_{K_{\text{dp}},i}+\ W_{\rho_{\text{hv}}}\beta_{\rho_{\text{hv}},i}}{W_{Z_{\text{dr}}}+\ W_{K_{\text{dp}}}+\text{\ W}_{\rho_{\text{hv}}}}\right]\beta_{T,i}\text{\ β}_{Z_{h},i}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (2)\nonumber \\ \end{equation}\begin{equation} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \beta=\ \frac{1}{1+\left[\left(\frac{x-m}{a}\right)^{2}\right]^{b}}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (3)\nonumber \\ \end{equation}
Where, μi is the fuzzy logic score for the ith hydrometeor type. βj,i is the membership function for ith hydrometeor types and jth variable (Equation 3). Wj is the weight factor for the jth variable. The values of these membership function parameters and the weights are taken as in Dolan et al. (2013), which are obtained from simulation at C-band. Five variables viz. Zh, Zdr, Kdp, ρhv and temperature (T) are used to calculate the fuzzy logic score. Seven types of hydrometeors have been considered viz. drizzle (DZ), rain (RN), ice crystals (CR), aggregates (AG), low-density graupel (LDG), high-density graupel (HDG), and vertically oriented ice (VI). Graupels are ice particles with diameter of 2-5 mm, which grow mainly due to riming process i.e., collection of supercooled water droplets onto the surface of ice crystals and subsequent freezing. Temperature for the HID scheme has been obtained from radiosonde measurements by IMD Thiruvananthapuram at 5:30 IST (Indian Standard Time). Radar data interpolated on a 0.5x0.5x0.5 km grid have been used for the HID analysis.