Diagnosing the Sensitivity of Particulate Nitrate to Precursor Emissions Using Satellite Observations of Ammonia and Nitrogen Dioxide
Ruijun Dang, Daniel J. Jacob, Shixian Zhai, Pierre‐François Coheur, Lieven Clarisse, Martin Van Damme, Drew C. Pendergrass, Jin‐soo Choi, Jinsoo Park, Zirui Liu, Hong Liao
Abstract
Abstract Particulate nitrate is a major component of fine particulate matter (PM 2.5 ). Its formation may be varyingly sensitive to emissions of ammonia (NH 3 ), nitrogen oxides (NO x ≡ NO + NO 2 ), and volatile organic compounds (VOCs), depending on local conditions. Diagnosing these sensitivities is critical for successful air quality management. Here, we show that satellite measurements of tropospheric NH 3 and NO 2 columns can be used as a quick indicator of the dominant sensitivity regime through the NH 3 /NO 2 column ratio together with the NO 2 column. We demonstrate the effectiveness of this indicator with the GEOS‐Chem chemical transport model and define thresholds to separate the different sensitivity regimes. Applying the method to wintertime IASI and OMI observations in East Asia reveals that surface nitrate is dominantly VOC‐sensitive in the southern North China Plain (NCP), NO x ‐sensitive in most of the East China Plain, and NH 3 ‐sensitive in the northern NCP, southern China, and Korea.