The latest measurements from the National Oceanic and Atmospheric Administration shows the American West is in for another dry La Niña winter, unwelcome news for the West currently struggling to keep flowing its main source of water: the shrinking Colorado River.
“That’s the worry in the present situation is that the odds now are now with La Niña are tilted against a really wet winter, at least in the southern half of California which of course has already been really dry,” said Dan Cayan, a research meteorologist at the Scripps Institution of Oceanography.
La Niña is kin to El Niño, the more well-known other half of a global climate phenomenon called ENSO, the El Niño-Southern Oscillation. It’s one of the biggest factors determining whether San Diego will have a wet winter – its rainiest season and key for refilling reservoirs and replenishing groundwater –or one that’s bone dry, compounding the existing drought and fire potential of the landscape.
ENSO acts like a giant switch, flipping between seasons of El Niño and La Niña every few years. For southern California, generally speaking, El Niño is rainier than its dryer sister season, La Niña. The federal government closely tracks it.
One way to think about ENSO is as a big circulation of heat and water around the planet, from ocean currents to air currents in the atmosphere. It’s born in the hottest and wettest place on Earth: The tropics at Earth’s equator.
The equator is the warmest part of the Earth because it gets the most consistent Sun. (The Earth’s poles tilt toward or away from the Sun depending on the planet’s journey around the Sun). Water evaporates as it warms there and rises into the atmosphere, cooling as it travels, until it becomes a cloud or rains back down.
And as that water evaporates, it releases an extraordinary amount of heat into the atmosphere. As that heat builds, it alters pressure in the atmosphere and the winds over the immense tropical Pacific. That heat has to go somewhere, and it takes quite a while to get where it’s going.
A lot of it migrates across the vast Pacific Ocean in slow, deep ocean waves that take months to reach the other side. That circulating heat energy generates these somewhat predictable weather patterns that we recognize as the switch between El Niño and La Niña. Sometimes one will stick around for a few months, other times, like we’re experiencing now, La Nina sticks around for a few years in a row – what scientists are calling the “triple dip” La Niña, as December marks its third winter in southern California.
The Pacific Ocean passes the inverse across the basin. When southern California is having a dry, La Niña spell, that means it’s raining in southeast Asia, which is having some of the wettest years on record.
La Niña seasons usually bring less snow to the Rocky Mountains, the source of that river’s flow, and to the Sierra Nevada mountains, which quench central California’s agriculture economy and major cities all the way down to San Diego.
One thing meteorologists are counting on to now break the drought: A big atmospheric river, like a river of rain in the sky, bands of concentrated moisture flowing through the atmosphere in the middle latitudes of the Earth.
“They are really important in delivering water supply,” Cayan said. “Our hope is that phenomena is more active than it was last year.”
In Other News
- San Diego is staring at a big bill to start collecting food waste. A measure on November’s ballot could help it pick up the tab. (Voice of San Diego)
- Speaking of food waste, the local Salvation Army branch is collecting it and redistributing it to individuals experiencing homelessness. (NBC 7)
- California water agencies are quietly negotiating an up to 400,000-acre foot reduction in its Colorado River use. (Desert Sun)
- Renewables provided 36 percent of the state’s power supply on average so far this year. California has 23 years to reach 100 percent, per its own lofty climate goals. (POLITICO)
- I consider this a drought poem: “The World I Can’t Remember is Now,” by New Mexico State’s Poet Laureate. (Five South)
- Gov. Gavin Newsom vetoed $100 million in state funding to address water quality problems in the cross-border Tijuana and New Rivers.
- South Bay beaches closed again after another pipe break in Tijuana. (Union-Tribune)
- California is attempting to ban foil balloons, which are often the cause of electrical fires along utility lines. (Union-Tribune)