California’s Vanishing Clouds Could Intensify Drought

Overpopulation and the Drought

• Zero Population Growth  -  I have totally come around to zero population growth.  Enough people have come to the People's Republic.
• Now we see man made urban heat islands as one of many factors in California's drought. And California is rapidly becoming one giant heat island as every possible open space in the Bay Area or Southern California is being paved over with concrete and asphalt.

(KQED News)  -  Fog season is with us once again. And whether it’s the ground-level “pea soup” of legend or the looming overcast known as the marine layer, there’s a reason it’s called California’s natural air-conditioning: fog and clouds are vital cogs in keeping the coastal thermostat turned down.

But that advantage could be disappearing.

KQED Science Editor Craig Miller talks with climate scientist Park Williams about his recently published work on California’s vanishing clouds.  Williams is an assistant research professor at Columbia University’s Lamont-Doherty Earth Observatory in New York, but the gray mantle of the California’s summer coastline keeps drawing him back here — and it’s not just the romance of it. It turns out that fog — any kind of cloud, actually — is a great regulator not just of heat, but of drought.

Park Williams: Yeah, fog regulates drought. It does it in a couple of ways. In ecosystems, fog drops water directly on plants. And when the water collects on the plants, it then drops into the soil and is available for the plants to use. Fog, and clouds that are higher than fog, also shade the sun, and that allows plants more time to use the water they’ve collected from the fog. In cities, fog and clouds that are higher than fog — overcast clouds — are important as well, because they regulate surface temps.

Craig Miller: And it seems like cities are where the problem is.

PW: We looked at Southern California and found that in large cities — L.A. and San Diego — the heights of low clouds during summertime have been increasing; they’ve been rising away from the city.

CM: Why would that be?

PW: Cities have been warming, and essentially you need to go higher into the atmosphere before you finally get to where it’s cool enough to have water droplets condense and clouds can form.

CM: This is sounding like the “urban heat island” effect at work here. Is there a smoking gun for that?

PW: The minimum temperature at night has been rising rapidly. During the daytime we’ve seen slow warming, but not nearly at the pace that nighttime warming is. That’s the fingerprint of the urban heat island that we expect. The urban heat island effect really is a nighttime phenomenon because cement takes a long time to get rid of its heat, and that causes nighttime temperatures to rise.

CM: And where urbanization reaches inland, like, say, the Inland Empire region east of L.A., this phenomenon seems to follow. For example, looking at readings from airports, you found there’s 87 percent less fog in Ontario since 1950, and that overall cloud cover — technically the “frequency” of clouds — has been reduced by about half. That’s stunning.

PW: That means Ontario is getting a lot more sunlight in the morning hours, which is then feeding back to heat up Ontario and make clouds less likely in the future.

CM: You’re describing a kind of vicious cycle.

PW: Clouds will become thinner over Los Angeles. That allows more sunlight to be absorbed by the ground, which causes more surface heat, which causes clouds to have to form higher up, which causes clouds to be thinner, which perpetuates this process of more sunlight, higher clouds — and eventually more sunlight, no clouds.

Read More . . . .

Science of Fog: Science on the SPOT

San Francisco's fickle summer weather has earned it the nickname "Fog City." Science on the SPOT asks UC Berkeley's Todd Dawson to clear up the mysterious origins of this weather phenomenon, and share his research on how fog is integral to our state's ecology.

Coastal Fog and the Drought
There’s 87 percent less fog in Ontario since 1950, and that overall cloud cover — technically the “frequency” of clouds — has been reduced by about half.