Validation of Ozone Monitoring Instrument nitrogen dioxide columns

Date

2008-05-07

Department

Program

Citation of Original Publication

Celarier, E. A., et al. "Validation of Ozone Monitoring Instrument nitrogen dioxide columns" J. Geophys. Res. 113,D15S15 (07 May, 2008). doi:10.1029/2007JD008908.

Rights

This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0

Subjects

Abstract

We review the standard nitrogen dioxide ( NO₂ ) data product (Version 1.0.), which is based on measurements made in the spectral region 415–465 nm by the Ozone Monitoring Instrument (OMI) on the NASA Earth Observing System-Aura satellite. A number of ground- and aircraft-based measurements have been used to validate the data product's three principal quantities: stratospheric, tropospheric, and total NO₂ column densities under nearly or completely cloud-free conditions. The validation of OMI NO₂ is complicated by a number of factors, the greatest of which is that the OMI observations effectively average the NO₂ over its field of view (minimum 340 km ²), while a ground-based instrument samples at a single point. The tropospheric NO₂ field is often very inhomogeneous, varying significantly over tens to hundreds of meters, and ranges from <10 ¹⁵ cm ⁻² over remote, rural areas to >10 ¹⁶ cm ⁻² over urban and industrial areas. Because of OMI's areal averaging, when validation measurements are made near NO₂ sources the OMI measurements are expected to underestimate the ground-based, and this is indeed seen. Further, we use several different instruments, both new and mature, which might give inconsistent NO₂ amounts; the correlations between nearby instruments is 0.8–0.9. Finally, many of the validation data sets are quite small and span a very short length of time; this limits the statistical conclusions that can be drawn from them. Despite these factors, good agreement is generally seen between the OMI and ground-based measurements, with OMI stratospheric NO₂ underestimated by about 14% and total and tropospheric columns underestimated by 15–30%. Typical correlations between OMI NO₂ and ground-based measurements are generally >0.6.