Linking Rainfall Microphysics to Intensity Using the \:D_m–R–\:N_w Relationship Over the Northeastern Indian Subcontinent: Implications for GPM DPR Retrievals

We investigate the relationships among the mass-weighted mean diameter ( \:D_m ), normalized intercept parameter ( \:N_w ), and rainfall rate ( R ) using five disdrometers and GPM Dual-frequency Precipitation Radar (DPR) observations over the northeastern Indian subcontinent. By extending the conventional \:D_m – \:N_w framework to include rainfall rate, we directly link rainfall microphysics to rainfall intensity. Rainfall with 1.5 ≤ \:D_m < 2.5 mm exhibits a bimodal structure in the \:D_m – R – \:N_w relationship, consisting of Type A rainfall ( \:N_w ≥ 36 dB) with high rainfall rates and Type B rainfall ( \:N_w < 36 dB) with lower rainfall rates. Type A rainfall is more frequent during the monsoon season and over orographic regions. The DPR product shows limited variability in \:N_w and rarely reproduces high- \:N_w rainfall, leading to systematic underestimation of rainfall intensity. These results highlight the importance of representing \:N_w variability for improving satellite-borne precipitation radar retrievals.