"speculated impacts"
Last year, they were speculative; this year they happened. It's happened here, too. It turns out that fruit trees understand climate change better than you do.
California’s Central Valley sees big drop in wintertime fog needed for fruit and nut crops
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American Geophysical Union / Joint Release / 20 May 2014
news.agu.org
California’s winter tule fog — hated by drivers, but needed by fruit and nut trees — has declined dramatically over the past three decades, raising a red flag for the state’s multibillion dollar agricultural industry, according to new research.
Crops such as almonds, pistachios, cherries, apricots and peaches go through a necessary winter dormant period brought on and maintained by colder temperatures. Tule fog, a thick ground fog that descends upon the state’s Central Valley between late fall and early spring, helps contribute to this winter chill.
“The trees need this dormant time to rest so that they can later develop buds, flowers and fruit during the growing season,” said University of California, Berkeley biometeorologist and study lead author Dennis Baldocchi, whose father grew almonds and walnuts in Antioch and Oakley. “An insufficient rest period impairs the ability of farmers to achieve high quality fruit yields.”
Tule fog drifts through a walnut orchard south of Meridian, along the Sacramento River. Copyright Anthony Dunn Photography. For reprint permission, go to adunnphotography.com
The study, published May 15 in the journal Geophysical Research Letters, a journal of the American Geophysical Union, has implications for the entire country since many of these California crops account for 95 percent of U.S. production, the authors noted.
The researchers paired NASA and National Oceanic and Atmospheric Administration satellite records with data from a network of University of California weather stations, covering 32 consecutive winters. There was a great deal of variability from year to year, but on average, the researchers found a 46 percent drop in the number of fog days between the first of November and the end of February.
“The year-to-year variability we saw was likely influenced by whether the season was relatively wet or dry,” said Baldocchi, a professor in UC Berkeley’s Department of Environmental Science, Policy and Management. “Generally, when conditions are too dry or too wet, we get less fog. If we’re in a drought, there isn’t enough moisture to condense in the air. During wet years, we need the rain to stop so that the fog can form.”
Central Valley fog
A satellite image shows a thick bank of fog blanketing the Central Valley of California. A new study finds that tule fog, a thick ground fog that descends upon the Central Valley between late fall and early spring, has declined dramatically over the past three decades.
Other studies have marked the decline in the Central Valley of winter chill – the number of hours between 0 and 7 degrees Celsius (32 and 45 degrees Fahrenheit). The number of hours of winter chill has dropped by several hundred since the 1950s, the study authors noted.
But ambient air temperature alone may not adequately reflect the heat experienced by the crops, said Baldocchi. Direct sunlight can heat the buds so that they are warmer than the surrounding air temperature. As a result, fog is important in shielding the buds from the sun and helping them accumulate winter chill.
Climate forecasts suggest that the accumulation of winter chill will continue to decrease in the Central Valley. Baldocchi said that fruit developers are already trying to develop cultivars that can tolerate less winter chill.
“Farmers may also need to consider adjusting the location of orchards to follow the fog, so to speak,” said Baldocchi. “Some regions along the foothills of the Sierra are candidates, for instance. That type of change is a slow and difficult process, so we need to start thinking about this now.”
The study was co-authored by Eric Waller, a UC Berkeley Ph.D. student in the Department of Environmental Science, Policy and Management. The California Energy Commission supported this research.
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"the other day record overnight lows here in CT"
We're getting record overnight lows, too, but on the upside.
Heat, Smoke, and Fire Assault Western States: All-Time Record Heat in California
Bob Henson · September 3, 2017, 4:35 AM
The steamy, fiery summer of 2017 hit a new crescendo this weekend across the U.S. West, which is getting its hottest Labor Day weekend on record in many locations—and in some spots, the hottest weather ever observed. Overall, “this is the greatest statewide heat wave ever recorded in California,” proclaimed WU weather historian Christopher Burt on Saturday night. Burt based his conclusion not only on the heat’s intensity but on its widespread nature well beyond California’s usual scorching locations. Even an escape to the cool Pacific shore was pretty much futile, as easterly downslope winds funneled scorching air from the interior into coastal sections that are normally mild and sometimes chilly even in midsummer. Readings also soared above 110°F across California’s Central Valley, although such heat is not quite so unusual for late summer in that area.
California’s Bay Area has been the focal point of the weekend’s most extraordinary heat. Temperatures soared to 106°F in downtown San Francisco on Friday and 102°F on Saturday. Friday’s reading was the hottest ever measured in downtown SF, where temperatures have been observed since 1874. Friday’s 106°F handily topped the previous record of 103°F from June 14, 2000, and Saturday was only the second high of 102°F in downtown history, matching Oct. 5, 1987. “To put this in perspective, the average high temperature for the city these two days is just 71°F,” said Chris Burt, who lives in the East Bay region. “Friday night’s temperatures failed to fall below 85°F at several hill locations near me (I dropped to 81°).” He added: “It is so hot in our home I can hardly think. No air conditioning, of course.” Heat-related illnesses overwhelmed San Francisco hospitals on Friday, according to the Bay Area NWS office. It would not be shocking to see multiple Bay Area fatalities during this heat wave, given the multi-day intensity of the heat and the Bay Area’s lack of air conditioning.
wunderground.com |
