Accretion (meteorology) Accretion (meteorology) Accretion is defined as the gradual collection of something over time. In meteorology or atmospheric science it is the process of accumulation of frozen water as precipitation over time as it descends through the atmosphere, in particular when an ice crystal or snowflake hits a supercooled liquid droplet, which then freeze together, increasing the size of the water particle. The collection of these particles eventually forms snow or hail in clouds and depending on lower atmosphere temperatures may become rain, sleet, or graupel. Accretion is the basis for cloud formation and can also be seen as water accumulates
Hail the hail to the radar, and the echo is further away from the radar than the actual location of the hail on the same radial path, forming a cone of weaker reflectivities. More recently, the polarization properties of weather radar returns have been analyzed to differentiate between hail and heavy rain. The use of differential reflectivity (formula_1), in combination with horizontal reflectivity (formula_2) has led to a variety of hail classification algorithms. Visible satellite imagery is beginning to be used to detect hail, but false alarm rates remain high using this method. The size of hailstones is best determined by