VOA常速英语:美国航空航天局计划太空测量积雪

Snow blankets cold regions of the earth, and these time-lapse images from NASA weather satellites.But while satellites can detect the surface of snow, snow’s reflective nature makes it hard to tell whether it’s thin or deep.

For that, Forest Service scientist Frank McCormick says experts (need) to do some digging.“They’ll dig a snow pit down to bare ground so that they can take very detailed measurements —everything from temperature to water that’s in the snow.”This accurately reviews snowpack’s water content.But on a global scale, digging snow pits isn’t practical.“We would need thousands upon thousands upon thousands of sites throughout the world.”

That’s why NASA has launched “SnowEx”.It’s a five-year project to design a snow satellite that will accurately measure snowpack everywhere.

SnowEx Project Leader Edward Kim says knowing snowpack’s water content,when it’s likely to melt and so on, could help over a billion people.“One out of every six people in the world depends most of their, the majority of their water that they use for drinking and agriculture and industry, comes from snow.”

To design the snow satellite, 100 SnowEx scientists are seeking the best ways to remotely measure snowpack’s depth,its water content, how surface dust and temperature affect snow, and more.As a first step, they’re putting snow sensors on airplanes.“The airplanes carry the sensors of the same type that would eventually be on a satellite.”

Snowy Colorado is the first SnowEx testing site.As pilots fly, scientists direct 10 kinds of sensors at the snow, including microwave and laser.They’re seeking accuracy even when terrain is uneven or when trees hide snow.

As for which sensors work the best, “Well, that’s really hard to say.I mean, if we really knew the answer of that already, we wouldn’t need to do this.”

To fine-tune airborne measurements, the SnowEx team will compare them with snow pit data.SnowEx scientist Charles Gatabe says fitting it all together will require complex calculations,but at its heart, the goal is simple:“Get the data, look at the data, and you know say what the data is telling us.

There’s so many people dependent on snow and given this changing climate, who knows what happens?So if we can get a very good handle how to predict,you know, the changing snow, and the changing climate, I think it’s going to benefit a lot of people.”

NASA’s SnowEx team plans to share their data in open access to help people around the world, wherever there is snow.

For VOA News, I’m Shelley Schlender, at the Peterson Air Force Base, in Colorado.