Everything you want to know about June gloom

june-gloom-vdt.jpgIt's been pretty dang nice along the beaches so far in these final days of official spring. But as anyone with very many summers in Los Angeles knows, a marine layer could blanket us in a deep, gray, soul-sucking June gloom at any moment. In fact, I hate to tell you, but a quick look look at the weather report for Santa Monica and Venice calls for "morning low clouds and fog" on Monday — and every day right through next weekend.

Science writer Cameron Walker got to thinking about Southern California's propensity for June gloom and notes that it's not much different than what people who live near the coast in Oregon and Washington experience. But here it has a name and some weather page lore behind it — "perhaps we give it a name (and May Gray, and, in dire situations, No-sky July and Fogust) because we complain about it the most." She talked to a scientist at Scripps Institution of Oceanography in La Jolla about where the gloom comes from. — and why. Excerpt:

Different parts of the coast offer their own complications, but generally speaking, the cold Pacific water—aided and abetted by the California Current and the upwelling—and a high pressure region, the Pacific High, conspire to form the marine layer clouds that some of us call gloom.

Usually, the atmosphere gets colder as you head up. But the cold water creates a situation where the air near the water’s surface is colder than the air above it: an inversion. The Pacific High pushes air downward, compressing it and warming it. Together, this forms a stable inversion air that can hold a layer of cloud near the water’s surface like an older brother crouching on an upstart sibling.

Gloom often dissipates in the afternoon, as sunshine warms air near the surface. The warmer air mixes into the clouds and starts to break them up.

Of course, there’s a lot more than that going on, too. The gloom is the home of a wild kind of cloud field called actinoform clouds, which, to a satellite’s eye, look like enormous leaves or pinwheels. And the ocean itself might be providing more than just cold water. Iodide released by kelp may turn into cloud condensation nuclei, which could make clouds thicker and more pervasive.

You can read up much more at a Scripps page on the marine layer. The staff in the Center for Atmospheric Science and Physical Oceanography at Scripps are having a contest among themselves to guess how many days of June gloom the coast will experience in May and June.

Previously on LA Observed:
Beauty of the swirling winds and a von Kármán vortex street

Photo: On the beach in Malibu in May, by Veronique de Turenne

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