SAN DIEGO – (INT) – California may be dealing with a lot of weather in the coming years and it could test the extremes.

There’s a new study led by Scripps Institution of Oceanography at UC San Diego.

The study, published Tuesday in the journal Nature Scientific Reports, looked at climate scenarios from 16 global climate models focusing on western North America. All 16 predicted that most of the heavy precipitation that the West receives in the future will come from the vast streams of moisture in the sky known as atmospheric rivers. A single atmospheric river typically carries twice the amount of water flowing in the entire Amazon River.

"As Mediterranean climate regions around the world are becoming more subtropical, the dry season is expanding. California is no exception," Scripps climate scientist and study lead author Alexander Gershunov said. "What is exceptional about California is that the heavy precipitation is projected to become more extreme."

Here's what scientists expect to happen:

—Overall precipitation will be about the same or slightly more over the long term. But it will progressively become more dramatic — more will fall in extreme bursts, increasing the possibility of flooding. Daily precipitation will become less frequent as there will be fewer storms not related to atmospheric rivers (ARs).

—California will not be able to rely on mountain snowpack to portion out water from melting snow. Because atmospheric river storms are warmer, snow levels will be higher. Driving rain will wash away snowpack at lower elevations. As the Sierra Nevada acts as a barrier to easterly moving storms, "California's topography is ideally aligned to extract increasingly heavy precipitation from strengthening ARs," the study said.

—Due to the unpredictability of snowmelt, resource managers may have to overhaul the state's water storage procedures. So far this century, there have only been four wet years — 2005, 2011, 2017 and 2019. In 2015, amid California's five-year drought, the Sierra Nevada received only 5 percent of its normal snow accumulation.

—Periods of drought will become more numerous and lengthy, but California is not projected to dry as severely as other Mediterranean climate regions around the world.

—The state will experience a feast-or-famine rainfall scenario — drought vacillating with flooding.

The federal Bureau of Reclamation, the Southwest Climate Adaptation Science Center, NOAA, the U.S. Geological Survey, and NASA funded the study.

Story Date: August 25, 2019