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How much water in that snowpack? Scientists seek a better gauge.

More accurate, more frequent measurements of mountain snowpacks will allow water managers to mete out reservoirs with greater confidence. Two watersheds in the western US are testing grounds for a new aerial approach.

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"Dust dramatically increases the amount of solar radiation absorbed by the snow," explains Jeffery Deems, a researcher with the National Snow and Ice Data Center in Boulder, Colo., and a member of Painter's team. At this stage of global warming's evolution, "the direct impact of dust on snowmelt is far greater than the direct impact of greenhouse warming on snowmelt."

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For the snowpack feeding the Colorado River, the dust is coming from New Mexico, Arizona, and Utah, he notes.

Indeed, that research – which Painter, Dr. Deems, and colleagues published in 2010 – prompted the JPL scientist to wonder if snow in the Tuolumne basin might be affected by dust kicked up in the nearby San Joaquin Valley or even coming across the Pacific from Asia.

Indeed, the team's instruments have recorded "a pretty good-sized dust signal in the mountain snowpack," Painter adds. The scientists are analyzing the dust to see if they can pinpoint its origin.

The tools the team is using also cover a wider swath of the ground with each pass than do the sensors aboard the National Operational Hydrologic Forecasting Center's aircraft.

This has allowed the team to put hard numbers to a region of the Tuolumne watershed that managers had long suspected of harboring the watershed's largest volume of snow-stored water. But the region is so inaccessible that it was difficult to make the on-the-ground measurements needed to show how important that patch of the watershed is.

The use of NASA's snow observatory won't replace ground measurements, notes Frank Gehrke, a co-investigator on the project who heads the California Department of Water Resources' Cooperative Snow Surveys Program. These proved to be a reality check on the aerial measurements and can provide direct measurements of snow density, which also are key to estimating water content, he explains.

But so far, the aerial data taken during April seems to be demonstrating the observatory's worth.

The project also has federal forecasters rooting from the sidelines as they anticipate better data on a vital resource.

"We've been paying attention to this project for quite some time," says the Hydrologic Forecasting Center's Mr. Rost. "We're cheering Tom on."


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