The U.S. National Weather Service's 156 Nexrad Doppler radar stations gather a tremendous amount of data. They scan the country in five- to 10-minute intervals, 24 hours a day, from 0.5 degrees above the horizon to 19.5 degrees. And in doing so, they detect much more than weather. Anything in the air bounces a signal back—insects, birds, wind turbines, low-flying planes, forest-fire smoke, falling meteors, debris from NASA disasters, and bats. Radar scientists call the signal from flying animals bioclutter. "From a meteorological standpoint, it's noise," Howard says. "It contaminates all our algorithms. It misleads people. We have examples that look like severe storms, but it's actually bats coming out of the ground."