How 'Atmospheric Rivers' Are Bringing Rain And Snow To California

California is getting some wet weather this week, and it's all because of a phenomenon called Atmospheric Rivers — long, relatively narrow regions in the atmosphere that transport water vapor, which is then released as rain or snow.

Marty Ralph, a research meteorologist and the director of the Center for Western Weather and Water Extremes at Scripps Institution of Oceanography, tells Here & Now's Meghna Chakrabarti that these "rivers in the sky" are essential to California's water supply — but can also lead to major flooding.