Posts Tagged rain

Dec 5 2014

Study: California Drought Most Severe Dry Spell in at least 1,200 Years


A car sits in dried and cracked earth of what was the bottom of the Almaden Reservoir south of San Jose on Jan. 28. (Justin Sullivan/Getty Images)

California’s current drought is pretty exceptional — like the driest in about a millennium — according to an article published today in the journal Geophysical Research Letters by scientists with the University of Minnesota and Woods Hole Oceanographic Institution in Massachusetts.

But how could they know that? There weren’t a lot of rain gauges in California in 800 A.D. — at least, not the plastic kind.

So authors Daniel Griffin and Kevin Anchukaitis looked to tree-ring samples from California blue oaks.

“California’s old blue oaks are as close to nature’s rain gauges as we get,” said Griffin, a NOAA Climate and Global Change Fellow with Woods Hole Oceanographic Institution. “They thrive in some of California’s driest environments.”

The researchers collected their own blue oak tree-ring samples from south and central California, giving them a pretty good idea of yearly precipitation in the area back to 1293. They then augmented their samples with data from the North American Drought Atlas and the National Oceanic and Atmospheric Administration Palmer Drought Severity Index.

The result: The study estimates that in the past 1,200 years, there have been 66 dry periods lasting three-to-nine years and 37 more-severe, three-year droughts. But not one of them has been as extreme as the one beginning in 2012, despite some years in the past seeing similarly low precipitation.

It’s not only lack of rain that makes a drought, though. Record-high temperatures added to California’s strife to make this dry spell the worst in more than 1,000 years, according to the study. The researchers estimate high temperatures have intensified the drought by about 36 percent.

UC Berkeley geology professor and researcher Lynn Ingram said the study’s findings appear solid.

“The tree-ring records provide the highest resolution as they have annual growth layers,” she said, adding the study provides a “cautionary lesson” about how human-caused warming “may already be impacting climate and water in California.”

Watch the California drought progress from the beginning of 2011 to the end of 2014 below. The NOAA U.S. Drought Monitor released the latest outlook today, up-to-date as of Dec. 2. More than half the state is now in “exceptional drought,” defined as “exceptional and widespread crop/pasture losses; shortages of water in reservoirs, streams, and wells creating water emergencies.”

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Nov 25 2014

Above-normal rainfall now predicted


The National Oceanic and Atmospheric Administration is predicting our area to experience above-average rainfall this season. (Photo: Provided/NOAA)


By the end of this week, be sure to start battening down the hatches.

Weather officials on Monday updated a rain outlook for the month of December, saying now that there will be above-normal rainfall moving toward the New Year that will have a significant effect on the drought outlook.

Logan Johnson, warning coordination meteorologist at the National Weather Service in Monterey, said above-normal precipitation is expected across the entire state during December, and that for central and southern California, the wet stuff is likely to keep coming throughout the rainy season, which runs through February.

“This very welcome news and should improve drought conditions statewide,” Johnson said.

In fact, according to Rich Tinker of the Climate Prediction Center at the National Oceanic and Atmospheric Administration, the above-normal rainfall this season is knocking the Central Coast down a notch on the U.S. Seasonal Drought Outlook.

Up until Friday, the majority of California was listed as an area where “drought persists or intensifies.” Now, because of soppy month ahead, the Central Coast and most of the rest of the state is listed as “drought remains but improves.” Temperatures, however, are expected to remain warmer than normal, which will further support this year as one of the warmest on record.

Forecasters say the above-normal precipitation headed this way during the rainy season should not be thought of as any kind of drought-buster. The region has experienced too many years of drought for it to end in one above-average year; it would take several above-average years to get the area back to normal.

The early part of this week is forecast for sunny autumn weather, but a high-pressure ridge is expected to break down on Friday, allowing a rain front to move into Northern California that will work its way south by Saturday.

“There remains uncertainty with regards to exact timing and amount of rainfall expected with this frontal passage,” according to a statement issued early Monday afternoon by the NWS.

A rain-friendly, upper-level, low-pressure system will move into the Bay Area Sunday and Monday bringing with it widespread rain, the NWS predicts, but ends with a cautionary note that the amount of rain cannot be accurately predicted since the forecast is projected out five to eight days.

“However, there is increasing confidence that the [San Francisco/Monterey] region will enter into a wet period that will last into early next week,” the NWS said Monday.

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