Marine Air Penetration in California’s Central Valley: Meteorological Drivers and the Impact of Climate Change

Abstract

AbstractThis study focuses on one of the most common coastal phenomena within California?s San Francisco Bay Delta and Central Valley?marine air penetration (MAP) events, which are a broad category of meteorological features that include the well-known ?delta breeze.? Summertime MAP episodes, identified by an inland cooling pattern and onshore wind, are selected in both observational and reanalysis datasets using a newly developed set of objective criteria. Correlations between MAP occurrence and synoptic-scale meteorological patterns are then examined to understand the drivers of MAP. Historical data are first used to determine whether any significant trends have been observed in the frequency and character of MAP events. Future trends in MAP are then predicted on the basis of an investigation of how synoptic-scale meteorological patterns will be modified in the twenty-first century under CMIP5 climatological projections. From the analysis of historical and future MAP frequency (under RCP8.5), a weak positive trend [~0.2 days (100 yr)?1] is identified in the occurrence of sufficiently strong summertime MAP days, although further study is needed.