From AGU: More urban heat; less summer fog, on California coast
Larry O’Hanlon writes on the AGU blog Geospace:
The summer fog that shrouds coastal southern California – what locals call the June Gloom – is being driven up into the sky by urban sprawl, according to scientists who have studied 67 years of cloud heights and urban growth in the region. Less fog may, at first, seem like a good thing. But less fog is bad news for native plants in the coastal hills and mountains, which depend on the cool fog as their only source of water during the rainless summer months. So less fog means warmer, drier, less healthy hillsides and potentially more fires.
What Park Williams of Columbia University’s Lamont-Doherty Earth Observatory in New York and his colleagues find is that the urban heat island effect – caused by concrete and asphalt retaining heat during the day and warming up the nights – is pushing up the moist coastal cloud layer. That turns what was once misty fog into a cloud layer that does not touch the ground.
“Los Angeles and San Diego have the strongest trends for rising cloud-bases and urban warming since 1948,” said Williams, regarding the two most heavily urbanized areas of southern California. “The Channel Islands (which are remote and undeveloped) and other locations have less strong trends.” The new findings were accepted for publication in Geophysical Research Letters (GRL), a journal of the American Geophysical Union.
Suspecting that increasing urban warmth might be driving fog and clouds upward, Williams and his colleagues dug into detailed, often hourly, meteorological data from the region’s many airports back to 1948. The data was trimmed to include observation times that all airfields had in common – 7 a.m., 10 a.m., 1 p.m. and 4 p.m. This was necessary because while some airfields – like Los Angeles – have nearly perfect hourly records around the clock, smaller airports which haven’t always operated at night sometimes had only daylight observations.
The researchers also used census-based estimates of household density in 1950 to estimate urban density within a 10-kilometer (6 mile) radius of the airports. For more recent years, they were able to use more accurate data from the National Land Cover Dataset. Since urban growth in much of southern California didn’t really take off until the latter half of the 20th century, there has been a lot of urbanization over those nearly seven decades.
What they found is that cloud-bottom heights have risen at airports where there was the most urban growth. The pattern is especially clear at at night and early morning, when fog is most common.
Full story here: http://blogs.agu.org/geospace/2015/03/05/urban-heat-less-summer-fog-california-coast/
Heat from the urbanization, or the effects of Jet exhaust?
At a large airport, I think the concrete wins that one. It’s a tossup in large city centers and (sub)urban sprawl where exhaust particulates may or may not come into play depending on whether prevailing winds favor the formation of inversion layers.
In the grand scheme of things, combustion heat itself is a rounding error. The planet absorbs in one hour about as much solar energy as human activities consume in an entire year.
And the effect of prevailing winds winding around the buildings, reducing air flow and cooling.
Yes. And at both the airport and inner city, pavement also has the effect of carrying away precipitation, leaving relatively less moisture to soak into the soils as in agricultural areas. Thus, paved areas get far less evaporative cooling.
Southern California coast has never had much fog. Occasionally in winter it has true ground-level fog, visibility less than 100 feet, not really in summer.
I’m old enough to recall a few facts. “Sexy” bathing suits were a hit in SoCal before anywhere else. Catalina started making bathing suits in LA in the 1920s, as did Cole of California. You don’t wear bathing suits in cold foggy conditions. This is why LA beaches have people sunbathing and dipping, while SF beaches have people in long pants and sweaters strolling in June.
Surfing was transplanted to Cali before WWII. In the 50’s surfing took off from Malibu to San Diego. Hobie Alter built his first surfboard in 1950. “Gidget, the Little Girl with Ideas” was written in 1957. The thing is you can’t surf in fog. You need to spot waves 200-400 meters out to position yourself, turn shoreward and paddle. In fog, you’re engulfed in foam before you can even turn around.
In 1961-63, I flew 3 times in early June from LA to Monterey with a stop in Santa Barbara. Once we flew above the clouds, twice under. I don’t know what the ceiling was, but it was high enough to fly with good visibility to the ground, 500 ft? 1000 ft? 1500 ft? I dunno but we weren’t skirting the white caps.
LA beaches had late-night/early morning stratus cover in the early 60s, which is to say, up at about 1000-4000 ft in the San Gabriels, there was true fog, but below, it was called overcast. Spending a few summers in Salinas, the sky was overcast, with sunlight breaking in the afternoon some days other days not, 8 miles from the Pacific, in June and July. Some light true misty light fog was to be had in Carmel, although 10 miles inland, in the village Carmel Valley, starry nights, very late at night and morning some overcast and sunny warm afternoons prevailed in June . LA beaches in June in the 50’s and 60’s had overnight overcast, stratus, not ground fog at the beaches and some miles inland, coming in from the sea after sunset, clearing in late morning to around noon in most mid-Junes.
The Southern California Bight slows and swirls the Japan Current inshore, near the SoCal coast. The inshore underwater landscape is generally shallow, so sunlight heats it up. In mid-June beaches from Redondo southward to San diego had water temps 59-64 most years in the 50’s and 60’s. Winds flowed onshore as air heatd and rose inland starting in mid morning and going until near sunset, as hot air rose in the desert and sucked ocean air in. Warm water caused fog to evaporate. By the wee house of the morning, the winds blew offshore. This was dry air. So at the coast, this dry warm air absorbed water droplets and vaporized them at lower elevations. This is why coastal SoCal in June didn’t have the true fog of Northern/Central Coastal California in June.
BTW, I spent a week in Redwood Country last August from Humboldt County to southern Mendocino. There was fog in the morning, and sometimes all day. The redwoods were spectacularly healthy. In 2011, I drove through the Santa Cruz Mountains. The redwoods were thick.
Dr. A. Park Williams, BS UC Irvine; MS,PhD UC Santa Barbara, appears to be a young formerly mediocre student, who is demonstrating that yes, there is room for third-rate “climate experts” on the federal-government-funded climate-fear-mongering gravy train.
California is undergoing a drought right now.But you should have seen the falls in Yosemite in summer ’11. They were fantastic. A water system that was designed to meet the needs of 25 million people and expand agriculture to the West Valley (a pretty much desert, but green able with water), is insufficient with 40 million people, and luddites convincing judges that reservoir-stored water must be free-flowing through the Golden Gate instead of being diverted to feed people, to save delta smelt, and no more dams can be built, because they are “unnatural”. For 1/10th the cost, the environmentalists could support building a delta smelt hatchery and transplant program. It worked for rainbow trout, in California, and as far east as Missouri, which didn’t have rainbow trout before hatcheries.
The term “fog” here is being used to depict what we coastal Californios typically call fog. Namely, coastal stratus. Not Tule / inland fog. That is for hoedads.
And the Japanese Current comes nowhere near California. You may be confusing it with The California Current which comes down here from the southern Gulf of Alaska.
James, Old Fart may be just using an antiquated name for the current because “Japan” and “California” are both names of sections of the same Pacific gyre. So in that sense the Japan current does finally reach the California coast under the name California current. The nit you are picking is sort of like saying the Gulf stream doesn’t get near Africa. An interesting question would be what has the precipitation been in the Coast Range north of Monterey on the Ocean side. When I lived there it was something like sixty inches a year due to fog, rain, and overcast. You know Mark Twain’s: “coldest winter I ever spent was summer in San Francisco”
Think microclimate and climate are the same thing? Think again:
http://www.metoffice.gov.uk/media/pdf/n/9/Fact_sheet_No._14.pdf
See especially page 16 on: Urban heat islands
Anyone got access to the original paper? Speaking as a VFR pilot I’ve got to say the measured cloud base height leaves a lot to be desired. Nowadays its measured automatically with a fixed vertical radar. I’m not sure how it was measured before that, it may have been a combination of pilot reports and visual estimates. You can also estimate the base height from the dew point spread in some conditions. I’m curious if the paper crosses any methodology changes.
They used projected light to do it. That was probably more accurate than radar methods.
Despite what even simple school kids’ experiments clearly show, CRU’s Dr Jones claims UHI doesn’t exist: “Jones et al. (1990) and Easterling et al. (1997) that urban effects on 20th century globally and hemispherically averaged land air temperature time-series do not exceed about 0.05°C over the period 1900 to 1990 “
Not buying it. Apparently nobody understands the difference between weather and climate, unless of course we are going to continue to partition climate areas down to 100×100 meter blocks. UHI certainly impacts local weather, but we are a long way of knowing whether it impacts the regional climate, partly because there is no consistent standard for what constitutes a “climate”. We don’t have near enough data to determine whether a few decades of changing UHI can change a climate, which has an unknown variable cyclicity measured in what – decades, centuries, aeons? You can make a case for UHI altering micro-climates, but we are a very long way from determining whether UHI affects continental climate zones.
When a survey asks the question, ‘are man’s actions affecting the climate?’, the answer, as this post shows, is yes. Just don’t go conflating that to mean CO₂ is to blame and we’re all going to hell in an hand cart.
See, there’s that pesky phrase “the climate” again.
When So Call turns into a full desert then we have climate change. Until then it is just a local environment change.
When So Cal turns BACK into a full desert………
This is from the pretty obvious dept; Microclimates are everywhere, but their effect on climate is nil. So many surface stations measuring microclimate by those who should and do know better and then claim to be measuring climate. My home affects the microclimate of my property where I can grow some plant materials on different sides of the house depending on specific conditions. Place the wrong plant or shrub in the wrong spot and it won’t do well or survive, but placed exactly in the right spot it may live long and prosper.
Perhaps someone has already raised it above but just in case I will ask anyway: has anyone bothered to reconstruct a land-based temperature time series corrected for the UHI effect? Historical data on population growth (if that is an appropriate proxy) must be readily available for most (all?) urban temp recording sites… Would be very interesting to see what the UHI effect-adjusted trends look like. Apology if im way behind the 8 ball and Willis or someone else has covered this already.
So finally, real evidence of man-made climate change! Really important study so thanks for highlighting Anthony. Whats the bet the cagw cultists and their co-conspirators in the MSM report the findings as evidence of man-made climate change – without explaining the absence of a greenhouse gas link…?