The soupy thick tule fog that regularly blanketed the Central Valley and terrorized unsuspecting motorists during the winter has been slowly disappearing over the past three decades, a University of California at Berkeley study has found.
The blinding mists may not be missed by those who remember white-knuckle drives in zero visibility and regular multiple-car pileups, but the fog dearth is bad news for farmers, according to a study published this month in the journal Geophysical Research Letters.
"It is jeopardizing fruit growing in California," said Dennis Baldocchi, a biometeorologist at UC Berkeley and lead author of the study. "We're getting much lower yields."
Baldocchi and co-author Eric Waller, a UC Berkeley doctoral student, used weather station data and compared it with satellite records and photographs kept by NASA and the National Oceanic and Atmospheric Administration during the past 32 winters.
The number of days when the valley was socked-in varied widely from year to year, he said, but the average amount of tule fog between November and the end of February declined 46% during the study period.
In 1980, for instance, there was an average of 37 foggy days in Fresno compared with 22 now. Long-term averages were used in an attempt to correct for times of drought. Only two foggy days were recorded this past winter, he said, and the decline is obvious to anyone who remembers how it once was.