ARB Research Seminar

This page updated June 19, 2013

Air Quality Management in California: Sensitivity to Changing Climate

Robert Harley, Ph.D., Department of Civil and Environmental Engineering, University of California, Berkeley

July 17, 2007
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Using a chemical transport model to simulate ozone concentrations in Central California, scientists at Berkeley evaluate the effects of variables associated with future changes in climate and ozone precursor emissions, including: (1) increasing temperature; (2) increasing atmospheric water vapor; (3) increasing biogenic volatile organic compound (VOC) emissions due to temperature change; (4) changing pollutant concentrations in Pacific Ocean inflow; and (5) projected decreases in anthropogenic emissions in California by 2050. The combined effect of changes (1)-(4) is to offset some of the benefits of reducing anthropogenic emissions (5); the offsetting effects are greatest in coastal areas.

Scientists also studied the effects of day-to-day temperature variability on motor vehicle-related VOC emissions using a chemical mass balance method applied to an 8-week summer season time series of speciated VOC measurements at Granite Bay (near Sacramento, California). The proportion of gasoline headspace vapors (relative to total vehicle-related VOC) in ambient air increases on hotter days as expected, though emission inventories may contain more vapor-type emissions than are reflected in atmospheric measurements. This analysis is relevant to understanding the effects of day-to-day meteorological variability and climate change on anthropogenic VOC emissions.

Speaker Biography

Robert Harley, Ph.D., is a professor in the Department of Civil and Environmental Engineering at the University of California, Berkeley, where he has been on the faculty since 1993. He holds a bachelor's degree in Engineering Science (Chemical Engineering option) from the University of Toronto, and both M.S. and Ph.D. in Environmental Engineering Science from the California Institute of Technology (Caltech). In addition to air quality modeling research, Dr. Harley has led a series of field measurement studies at the Caldecott tunnel that describe downward trends in California motor vehicle emissions and the effects of fuel changes on emissions.

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