Fog composition in the Central Valley of California over three decades

Pierre Herckes, A. R. Marcotte, Y. Wang, J. L. Collett

Research output: Contribution to journalReview articlepeer-review

38 Scopus citations


Numerous fog studies have been conducted in the Central Valley of California since the 1980s, making it one of the most studied locations in the world in terms of fog chemistry. The present work reviews observational fog studies in the area and discusses overall chemical composition as well as spatial variability and temporal variability. Regionally there is a clear gradient in fog occurrence with less fog and lower density (liquid water content, LWC) fog in the southern part of the Valley (Bakersfield) compared to more northern locations like Fresno or Davis. Chemically, fogs in the southern valley have higher solute loadings and lower pH compared to more northern locations (Davis and Fresno). Overall fog chemistry is dominated in the valley by the ammonia-nitric acid-ammonium nitrate system with sulfate being a rather minor component, especially at more northern locations and in more recent years. Fog pH in recent years is consistently higher than 5, showing an absence of acid in fogs in this region. LWC values appear to have decreased over recent years (less dense fogs). An airport visibility assessment of fog frequency reveals that overall dense fogs (visibility of less than 1/4. mile) have decreased by ~. 50% over the last 30. years.

Original languageEnglish (US)
Pages (from-to)20-30
Number of pages11
JournalAtmospheric Research
StatePublished - Jan 1 2015


  • Air pollution
  • Cloud
  • Fog
  • San Joaquin Valley
  • Temporal change

ASJC Scopus subject areas

  • Atmospheric Science


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