Weather forecasts may get precise soon

It has been a known fact for long that rain forecasts are flawed, as a lot of factors like evaporation are not taken into account.

The researchers at the University of Missouri-Columbia have developed a system that improves the precision of forecasts by accounting for evaporation in rainfall estimates, particularly for locations 30 miles or more from the nearest National Weather Service radar.

"Right now, forecasts are generally not accounting for what happens to a raindrop after it is picked up by radar," said a researcher, Neil Fox, "Evaporation has a substantial impact on the amount of rainfall that actually reaches the ground. By measuring that impact, we can produce more accurate forecasts that give farmers, agriculture specialists and the public the information they need."

 

A dual polarization radar was used ends out two radar beams polarized horizontally and vertically, to differentiate between the sizes of raindrops by researchers Fox and Quinn Pallardy. It was seen that the size of a raindrop affects both its evaporation rate and its motion, with smaller raindrops evaporating more quickly but encountering less air resistance.

This information combined with a model that assessed the humidity of the atmosphere, the researchers were able to develop a tracing method that followed 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.

It was found that the accuracy of the rainfall forecast had improved, especially in locations at least 30 miles from the nearest National Weather Service radar.

"Many of the areas that are further from the radar have a lot of agriculture," Fox said. "Farmers depend on rainfall estimates to help them manage their crops, so the more accurate we can make forecasts, the more those forecasts can benefit the people who rely on them."

The study has been published in the Journal of Hydrology.