Atmospheric rivers — significant sources of rainfall — tend to intensify during El Niño events, and this year's strong El Niño likely will bring more precipitation to California and some relief for the drought, according to new satellite research from NASA.
Duane Waliser, chief scientist of the Earth Science and Technology Directorate at NASA's Jet Propulsion Laboratory in Pasadena, California, and his colleagues analyzed the historical record of atmospheric rivers. These concentrated rain bands account for 40 percent of California's water supply. Their results suggest the number of atmospheric rivers California receives will remain the same, at an average 10 per year, but they will be stronger, warmer and wetter.
An El Niño, which is a recurring natural phenomenon, happens when sea surface temperatures in the equatorial Pacific Ocean warm up. The increased ocean surface temperatures influence air and moisture movement around the globe. Approximately 15 years of observations by NASA's fleet of Earth-observing satellites show how El Niños affect multiple interconnected Earth systems.
While California is likely get more precipitation, it may receive less in terms of snowfall, which could contribute to more flooding.
It's the strength of the El Niño that determines its impact on total rainfall in California, NASA says. Weak El Niños don't necessarily change the odds of precipitation being much different from normal, but the rare occurrence of a strong El Niño — like what we're currently experiencing — greatly increases the odds of a wet California winter.
El Niño's elevated sea surface temperatures shift rain patterns by affecting the temperature of the air above the ocean, which alters how winds and air masses circulate air around the planet, NASA says.
It will take around 11 trillion gallons of water — about 1.5 times the maximum volume of the largest U.S. reservoir — to recover from California's continuing drought, according to an analysis of NASA satellite data released late last year.
The promise of drought relief in California would be welcomed by the state’s massive agricultural industry, which is facing state-mandated water usage cuts. Other water-dependent industries, such as food processing, semiconductors and energy, also stand to benefit.
As El Niño continues to intensify, it is expected that global drought losses will surpass the current forecast $8 billion in economic damage, according to a report by Aon Benfield, the global reinsurance intermediary and capital advisor of risk management firm Aon. The report evaluated the impact of the natural disaster events that occurred worldwide during August 2015 and revealed that, in the United States, severe drought conditions persisted in western regions with total economic losses expected to reach at least $3 billion — mostly attributable to agricultural damage in California.