Fog is a common feature along the West Coast during the summer, but a University of Washington scientist has found that summertime coastal fog has declined since 1950 while coastal temperatures have increased slightly.
Fog formation appears to be controlled by a high-pressure system normally present off the West Coast throughout the summer, said James Johnstone, a postdoctoral researcher with the Joint Institute for the Study of the Atmosphere and Ocean at the UW.
"The behavior of that high-pressure cell is responsible for a lot of the weather phenomena we see on the coast," he said. It can alter water temperature, ocean circulation, surface winds and other factors linked to coastal fog formation.
The fog decline could have negative effects on coastal forests that depend on cool and humid summers, but Johnstone, who presents his findings Monday (Dec. 13) at the American Geophysical Union annual meeting in San Francisco, hasn't seen evidence of that yet.
In fact, climate models indicate that coastal fog should be increasing because of global warming, but he believes that is not happening because of strong influence exerted by regional circulation patterns related to the Pacific Decadal Oscillation. That climate phenomenon, centered in the North Pacific, has wide-ranging effects that last for years or even decades rather than for just a year or two.
"You would eventually expect to see significant effects on the coastal forests if the fog continues to decline," he said.
Johnstone examined records from airports up and down the West Coast that have taken hourly readings on cloud height for the last 60 years. He looked closely at two stations in particular, Monterey on the central California coast and Arcata on the northern California coast, and found that their decline in fog and increase in temperature matched very closely despite being separated by about 300 miles. Both also reflected a great deal of var
|Contact: Vince Stricherz|
University of Washington