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Speaker: Prof. Christopher Cappa, CEE, UCDavis

Time: 4:00p–5:00p

Location: 48-316

Environmental Sciences Seminar Series
Hosted by: Otto Cordero (ottox@mit.edu)
Serguei Saavedra (sersaa@mit.edu)

The San Joaquin Valley (SJV) of California suffers from some of the worst air quality in the US. This study combines airborne and ground observations made in Fresno, CA to assess the factors that contribute to the poor air quality. The observations demonstrate that production of particulate nitrate in the aloft nocturnal residual layer plays a critical role in determining surface-level concentrations during the daytime and contributes substantially to the build-up and sustaining of severe pollution episodes. An observationally-constrained 1D mixing model shows that mixing down of particulate nitrate from the nocturnal residual layer can explain much of the variability in the daytime surface concentrations, contributing most of the particulate nitrate in the morning (~80%) and nearly half in the afternoon when photochemical production is maximum. More generally, for species with substantial nocturnal production aloft and limited surface-level production or emission, entrainment of air from the NRL can lead to an increase, rather than decrease, in daytime ground concentrations. Additionally, the very shallow nocturnal boundary layer allows for moderate emissions from residential wood combustion to have a disproportionate impact on surface particulate matter concentrations.

Web site: https://sites.google.com/site/sergueisaavedra/seminar

Sponsor(s): Civil and Environmental Engineering

For more information, contact:
Denise Stewart