As a kid growing up in the Southland, I got my weather tips on the television from a mustached meteorologist named Dr. George. He would get quite excited when a big rainstorm was heading our way, breathlessly drawing pressure gradients and furiously waving a wand as if commanding a symphony. It felt like something epic and rare was about to happen.
I still find myself mesmerized by meteorologists and wonder if new insights into atmospheric rivers will move the needle with key California water decisions.
One of the experts in this emerging field of study is Martin Ralph of the University of California, San Diego, who is fast unraveling the mysteries of atmospheric rivers. I was one of about 2,000 water industry officials who attended his presentation a few months back at an Association of California Water Agencies conference. His presentation is available to view here.
For 25 years, I have lived in Sacramento, also known locally as the River City. Like most Sacramento residents, I have a strong connection with the rivers in our community. The biggest, the Sacramento, can transport up to 200,000 acre-feet (around 245 million cubic meters) of water past our town in a single day. That is a lot of water.
California has the most variable weather in the nation. (Metropolitan Water Agency)
Yet up in the sky, if an atmospheric river is blowing off the Pacific and roaring toward the Sierra, Ralph estimates that 100 times as much water is moving across the California skies in the form of vapor.
That is a stunning amount of moisture in motion. Put another way, a typical atmospheric river transports vapor equal to about 20 times the average flow of the Mississippi River. If 10 percent of that vapor ends up falling as rain and snow, that is one big storm event.
A California meteorologist’s job isn’t particularly consequential for 355 days out of the year. It is the 10 wettest days on the calendar that produce about half of our rainfall. In an “average” year, that is when the six to 10 atmospheric rivers head over the state. The moisture content of that river, and the percentage that actually reaches ground, largely shapes the rain year.
Ten precious days.
We in California have the most variable weather in the nation. Climatologically, we are as flaky as they come. Most of the variability in a year’s worth of weather is determined by only 5 percent of the days, and how wet they happen to be.
In some ways, technology is just beginning to precisely measure our own weather. Ralph’s team so far has been able to collect data from a mere 17 atmospheric rivers, using soda-can-sized sensors dropped from airplanes that parachute into the paths of the storms. A week before an atmospheric river reaches landfall, it’s anyone’s guess exactly where it will reach land. Could be San Francisco. Could be Santa Barbara. Or any number of places.
As we better understand our weather, will it actually shape how we manage water? That’s a less scientific question. For here in California, our variable weather is matched only by our volatile water politics.
Rationally, you would think that a society with this kind of variable weather would be completely united in developing water systems that could take full advantage of those 10 wettest days. That we would be united most of all when it comes to our largest surface water source – the Sierra Nevada range – and our largest water delivery systems located downstream in the Sacramento-San Joaquin Delta.
That, as the Mamas and the Papas sang, would take some serious California dreamin’, on such a winter day.
Let’s hope that we in the water industry can make the same progress as weather experts like Martin Ralph. Then, like Dr. George, we would have something to get truly excited about.
The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Water Deeply.
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