Characterizing the impacts of vertical transport and photochemical ozone production on an exceedance area

摘要

Offshore and inland vertical profiles of ozone (O-3) were measured from an aircraft during 16 flights from January 2012 to January 2013 over the northern San Joaquin Valley (SJV) and over the Pacific Ocean. Analysis of in situ measurements presents an assessment of the seasonality and magnitude of net O-3 production and transport within the lower troposphere above the SJV. During the high O-3 season (May -October), the Dobson Unit sum of O-3 in the 0-2 km above sea level (km.a.s.l.) layer above the SJV exceeds that above the offshore profile by up to 20.5%, implying net 03 production over the SJV or vertical transport from above. During extreme events (e.g. Stratosphere-to-troposphere transport) vertical features (areas of enhanced or depleted O-3 or water vapor) are observed in the offshore and SJV profiles at different altitudes, demonstrating the scale of vertical mixing during transport. Correlation analysis between offshore O-3 profiles and O-3 surface sites in the SJV lends further support the hypothesis of vertical mixing. Correlation analysis indicates that O-3 mixing ratios at surface sites in the northern and middle SJV show significant correlations to the 1.5-2 km.a.s.l. offshore altitude range. Southern SJV O-3 surface sites show a shift towards maximum correlations at increased time-offsets, and O-3 surface sites at elevated altitudes show significant correlations with higher offshore altitudes (2.5-4 km.a.s.l.). (C) 2014 Elsevier Ltd. All rights reserved.