how much snow falls worldwide each day–and where?
How much water falls to Earth in the form of light, drizzly rain? “These are just a few of the outstanding questions,” he says. Answering them would fill significant gaps in our understanding of the Earth’s climate system. What to do? “The best way to study global precipitation is from space.”Right: Artist’s concept of a space-based precipitation radar. Credit: Walter A. Petersen, NSSTC/UAH. That’s why NASA recently funded a suite of 59 research proposals under the agency’s ongoing Precipitation Measurement Mission. The studies will look at ways to improve measurements of rain and snow from Earth orbit. Petersen is among the winners, and one of the things he’ll be studying is snow: “Snow is a huge problem,” says Petersen. It turns out that estimating snowfall is very hard to do with radar. Rain is easier because it always consists of simple liquid-filled droplets. Radar echoes from rain clouds can be converted into rates of rainfall with fairly good precision. A radar onboard NASA’s Tr
