Applying an Evaporation Correction Scheme for Real-Time Radar-Based Instantaneous Rain Rates

Multiple limitations still exist with radar sampling and radar-based quantitative precipitation estimation (QPE) that present challenges in creating accurate surface precipitation estimates. One such set of challenges is the overestimation of precipitation and false light precipitation echoes in sub-saturated environments. An evaporation correction technique is being developed for the Multi-Radar Multi-Sensor (MRMS) system to help mitigate the impact of evaporation on precipitation between the radar beam level and the surface. The evaporation correction scheme utilizes model data to generate a three-dimensional profile of atmospheric conditions to modify the precipitation rate with respect to height. The scheme is based on the derivations by Gregory (1995), which originated from the theory of evaporation of a water droplet or ice particle through the rate of mass diffusion with respect to time. Different calculations are used for rain and snow throughout the vertical column of each grid cell, which is dependent upon the height of the freezing level and the lowest altitude of available radar data. Preliminary case study results show that the implementation of an evaporation correction scheme improved precipitation biases, removed false light precipitation, and improved gauge quality control with respect to the misclassification of false zero gauge observations.