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Quantifying the contribution of inflow on surface ozone over California during summer 2008
Author(s) -
Pfister Gabriele G.,
Walters Stacy,
Emmons Louisa K.,
Edwards David P.,
Avise Jeremy
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020336
Subject(s) - ozone , environmental science , tropospheric ozone , atmospheric sciences , troposphere , pollution , chemical transport model , climatology , air pollution , inflow , air quality index , meteorology , geography , chemistry , geology , ecology , organic chemistry , biology
Transported pollution has been recognized as making a potentially strong impact on air quality in the western U.S., but large uncertainties remain in quantifying its contribution. Assessing the role of pollution transport in relation to local emissions and meteorology is especially important in light of possibly lower ozone standards and projected increases in transpacific pollution transport. We apply the Weather Research and Forecasting with Chemistry model to analyze the role of upwind pollution (“inflow”) to surface ozone over California during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites campaign in June–July 2008 over California. Comparisons of the model to surface and aircraft observations, ozonesondes, and satellite retrievals show an overall good agreement; a low bias (~5 ppb) in free tropospheric ozone is attributed to low ozone at the boundaries and likely places our estimated inflow contribution on the lower side. Most other studies applied sensitivity analyses, while we use a synthetic ozone tracer, which provides a quantitative estimate of the budget. We estimate that on average 10 ± 9 ppb of surface afternoon ozone over California is attributed to ozone and ozone precursors entering the region from outside. This contribution features a significant spatial and temporal variability. While in most high ozone events, transported pollution plays a small role compared to local influences, for some instances, the impact can be substantial. Omitting data impacted by wildfires, we estimate the 90th percentile of the relative contribution of O 3 INFLOW to 8 h ozone >75 ppb as 10%. Our results also indicate that inflow might have a stronger impact on surface ozone in less polluted compared to polluted areas.