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Reporting on science, technology and innovation in Arizona and the Southwest through a collaboration from Arizona NPR member stations. This project is funded in part by the Corporation for Public Broadcasting.Additional stories from the Arizona Science Desk are posted at our collaborating station, KJZZ: http://kjzz.org/science

NASA Releases New Data on California’s ‘Rain Debt’

NASA/Goddard Scientific Visualization Studio

A new NASA study examines 36 years of precipitation patterns in California.

Researchers are using this information to learn more about the current drought and how much precipitation it would take to quench a thirsty state.

The NASA study estimates that from 2012 to 2015, California’s accumulated rain debt – or the difference between the actual rainfall and the average amount expected each year – is about 20 inches. This is about a year’s worth of rain and snowfall for the state.

Going back to 1979, the study combines information from two sources, said Doug Morton, earth scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“The data from the most recent study reflects a combination of our satellites that measure rainfall, and our weather forecasting and computer modeling approaches that allow us to take that information, along with gauge data, to provide an understanding of the longer term record of rainfall across the Southwest, and California in particular,” Morton said.

The scientists found that during another severe, multi-year drought between 1986 and 1994, California accumulated a 27.5 inch precipitation deficit.

And Morton said climate models project California and most of the Southwest will become warmer and drier, with more frequent and severe droughts.

Based on their significant water deficits, and based on the fact that groundwater has been used to compensate for the lack of rainfall, even a big year from El Niño is still just a drop in a leaky bucket for California. - Doug Morton, NASA earth scientist.

“There’s no end in sight to the California drought without some significant rainfall feeding the long-term historic means for the next several years,” he said.

The new information supports what some climatologists are saying about predicted El Niño conditions this winter: it won’t provide a quick fix for drought.

“Based on their significant water deficits, and based on the fact that groundwater has been used to compensate for the lack of rainfall, even a big year from El Niño is still just a drop in a leaky bucket for California," said Morton.

The study results were published July 30 in the Journal of Geophysical Research – Atmospheres. Morton was not a co-author on the study but is involved with similar NASA studies that look at rainfall and satellite data to examine climate variability.

Morton said this study is part a wider effort to use NASA satellites to gather information about drought and flooding in the United States.