June Gloom aside, Los Angeles has never been famous for its gray days or fog, but it does have them. Or at least, it used to. Researchers from Columbia University found that early morning and nighttime fog frequency over LA has dropped 63 percent since 1948, says CityLab. Using the hourly measurements of cloud heights that SoCal airports have taken over the past 70 years, researchers found that temperatures at night were higher and so, too, were cloud altitudes—a pair that together make a "clear sign of the heat island effect," referring to the higher temps that urbanized areas have when compared to their rural neighbors.
All day concrete traps heat; at night, all that heat is released, which kicks up nighttime temps. "These high temperatures near the ground prevent water droplets from condensing, so clouds form at a greater height than they otherwise would." This, along with a dearth of trees and the coverage they provide, is making it too warm for fog to form. "We're definitely more than 99 percent confident that we're seeing something very real here—it's not just a correlation," one of the study's authors says. (Meanwhile, California is having the warmest winter ever.)
But what LA gains in road visibility, it loses in everything but road visibility. That fog is a vital source of moisture—a "godsend"—for all the things that grow on the hills and mountains, not just because they need water to survive, but also because it makes them less than ideal tinder for SoCal's plentiful, devastating wildfires. Less fog could also mean that summertime temps will be even warmer than usual (and LA's usual can already get pretty gross), which no one would benefit from except air conditioning repair people and local ice creameries.
· Why L.A.'s Fog Is Disappearing [CityLab]
· Southern California's June Gloom Might Be Canceled This Year [Curbed LA]