Rainfall forecasts have flaws, failing to take into account factors such as evaporation. University of Missouri scientists have developed a system that improves the precision of forecasts by accounting for evaporation in rainfall estimates. Researchers use dual-polarization radar to differentiate between the sizes of raindrops. The size of a raindrop affects both its evaporation rate and its motion. By combining this information with a model that assesses the humidity of the atmosphere, the researchers were able to develop a tracing method that follows raindrops from the point when they were observed by the radar to when they hit the ground, precisely determining how much evaporation would occur for any given raindrop.