What is the spatial variability of column NO2? Implications for understanding OH and NOx lifetime
Abstract
The lifetime of NOx depends strongly on its own concentration via feedback on OH. As a result, the lifetime of NOx depends on the rate at which NOx mixes from a source (100s ppb) to the background (10s-100s ppt). Understanding the NOx lifetime requires an accurate understanding of the spatial scales at which NOx-OH feedbacks are most important. We run WRF-CHEM at 1, 4, 12, 24, and 48 km model resolution over California and over the Four Corners Power plant in New Mexico to determine the model resolution necessary to compute column NO2 to 10%. To compute column NO2 to 10% accuracy, we find that model resolution of 12 km is necessary over urban and area sources while 4 km resolution is necessary over point sources. To assess the observed spatial variability of NO2, we retrieve slant column NO2 from OMI test-phase observations in November 2004 that were sampled every 3 km on the surface and that have a spatial resolution of no greater than 7-9 km (FWHM). We find that slant column NO2 observed over a point source in India is no wider than 9 km as far as 25 km downwind. The same dataset shows that NO2 varies significantly (50-75%) at spatial scales of 12-24 km over Dubai and Seoul. These findings provide further support of model predictions discussed above; accurately capturing NOx-OH feedbacks requires understanding the variability of NO2 at scales of 4 km over a point source and of ~6-12 km over an urban source.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A21C0086V
- Keywords:
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- 0317 ATMOSPHERIC COMPOSITION AND STRUCTURE / Chemical kinetic and photochemical properties;
- 0322 ATMOSPHERIC COMPOSITION AND STRUCTURE / Constituent sources and sinks;
- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry