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Open AccessArticle

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

1
Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD 20740, USA
2
Cooperative Institute for Climate and Satellites, University of Maryland, College Park, MD 20742, USA
3
South Coast Air Quality Management District, Diamond Bar, CA 91765, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(7), 1001; https://doi.org/10.3390/rs10071001
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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