As Los Angeles Grows, June Gloom Fades

Los Angeles doesn't get much fog as our neighbors to the north get (hi SFist!), and it turns out our population growth has put it on the decline for decades. As nice as that sounds for our morning commutes, it turns out this is a bad thing for native plants and can potentially create more fires.A new study by Professor Park Williams from Columbia looked at 67 years of airport records from Santa Barbara down to San Diego and found that the fog in the region has declined 63% over that time period. Using census data, Williams found that the airports that experienced the most fog decline were in the most urbanized areas. Urbanization creates an effect known as the urban heat island, where heavily populated areas experience warmer temperatures through a number of factors, especially the absorption of heat by buildings and pavement.

This heat, in turn, prevents the formation of fog, which relies on cooler air temperatures. "When you increase the temperature of the surface of the Earth, then you essentially need to go higher up into the atmosphere before [it] is cool enough to promote condensation," he told KPCC.

Ontario Airport experienced the biggest decline in fog, with a 90% decrease over that timeframe. In contrast to urban airpots like those in Los Angeles and San Diego, airports in less-developed areas like Santa Barbara and The Channel Islands saw less of a decline.

As much as humans might appreciate not having to drive or fly through fog, this is bad for coastal ecosystems and plants. "Fog clouds deposit water directly on plants. This effect has been weakened," said Williams. During the dry summers, plants rely on the June Gloom as their main source of moisture. Less fog can mean drier brush, creating the ideal conditions for more wildfires.