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Open AccessArticle

A Conservative Downscaling of Satellite-Detected Chemical Compositions: NO2 Column Densities of OMI, GOME-2, and CMAQ

Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD 20740, USA
Cooperative Institute for Climate and Satellites, University of Maryland, College Park, MD 20742, USA
South Coast Air Quality Management District, Diamond Bar, CA 91765, USA
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(7), 1001;
Received: 19 May 2018 / Revised: 15 June 2018 / Accepted: 20 June 2018 / Published: 23 June 2018
(This article belongs to the Special Issue Remote Sensing Image Downscaling)
A conservative downscaling technique was applied when comparing nitrogen dioxide (NO2) column densities from space-borne observations and a fine-scale regional model. The conservative downscaling was designed to enhance the spatial resolution of satellite measurements by applying the fine-scale spatial structure from the model, with strict mass conservation at each satellite footprint pixel level. With the downscaling approach, NO2 column densities from the Ozone Monitoring Instrument (OMI; 13 × 24 km nadir footprint resolution) and the Global Ozone Monitoring Experiment-2 (GOME-2; 40 × 80 km) show excellent agreement with the Community Multiscale Air Quality (CMAQ; 4 × 4 km) NO2 column densities, with R = 0.96 for OMI and R = 0.97 for GOME-2. We further introduce an approach to reconstruct surface NO2 concentrations by combining satellite column densities and simulated surface-to-column ratios from the model. Compared with the Environmental Protection Agency’s (EPA) Air Quality System (AQS) surface observations, the reconstructed surface concentrations show a good agreement; R = 0.86 for both OMI and GOME-2. This study demonstrates that the conservative downscaling approach is a useful tool to compare coarse-scale satellites with fine-scale models or observations in urban areas for air quality and emissions studies. The reconstructed fine-scale surface concentration field could be used for future epidemiology and urbanization studies. View Full-Text
Keywords: downscaling; NO2 column density; OMI; GOME-2; CMAQ downscaling; NO2 column density; OMI; GOME-2; CMAQ
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MDPI and ACS Style

Kim, H.C.; Lee, S.-M.; Chai, T.; Ngan, F.; Pan, L.; Lee, P. A Conservative Downscaling of Satellite-Detected Chemical Compositions: NO2 Column Densities of OMI, GOME-2, and CMAQ. Remote Sens. 2018, 10, 1001.

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