Rainfall Rate Relationships in WSR-88D Rainfall Estimation Algorithms Dan Berkowitz Applications Branch Radar Operations Center

WSR-88D DP Z-R Relations The following rainrate (R) relations are used for the different hydrometeor types per the Hybrid Hydrometeor Classification algorithm and are a function of the melting layer R = R(Kdp) – Hail (HA) below melting layer (ML) R = R(Z,Zdr) – Rain (RA), Heavy rain (HR), and Big drops (BD) below ML R = R(Z) – Dry snow (DS) and Ice crystals (IC) below ML R = 0.6*R(Z) – Wet snow (WS) R = 0.8*R(Z) – Graupel (GR) and HA above ML R = 2.8*R(Z) – Dry snow (DS) and IC above ML

WSR-88D Z-R Relations RelationshipMethodDescription 300R^1.4Legacy Default Convective 250R^1.2Legacy Rosenfeld Tropical 200R^1.6 Legacy Marshall-Palmer 130R^2.0 Legacy East Cool Season 75R^2.0 Legacy West Cool Season R(Z,0.125dB)cont Dual PolContinental Light/Moderate/Heavy Rain or Big Drops(Zdr=0.125) R(Z,0.25dB)cont Dual Pol Continental Light/Moderate/Heavy Rain or Big Drops (Zdr=0.25) R(Z,0.5dB)contDual PolContinental Light/Moderate/Heavy Rain or Big Drops (Zdr=0.5) 2.8R(Z) Dual Pol Dry Snow Above ML & Ice Crystals 300R^1.4 Dual Pol Dry Snow In or Below ML 0.8R(Z)Dual PolHail Above ML & Graupel R(Z,0.125dB)trop Dual Pol Tropical Light/Moderate/Heavy Rain or Big Drops (Zdr=0.125) R(Z,0.25dB)tropDual Pol Tropical Light/Moderate/Heavy Rain or Big Drops (Zdr=0.25) R(Z,0.5dB)trop Dual Pol Tropical Light/Moderate/Heavy Rain or Big Drops (Zdr=0.5) 0.6R(Z) Dual Pol Wet Snow