An improved method for retrieving nighttime aerosol optical thickness from the VIIRS Day/Night Band

• Main Authors: T. M. McHardy, J. Zhang, J. S. Reid, S. D. Miller, E. J. Hyer, R. E. Kuehn
• Format: Article
• Language: English
• Published: Copernicus Publications 2015-11-01
• Series: Atmospheric Measurement Techniques
• Online Access: http://www.atmos-meas-tech.net/8/4773/2015/amt-8-4773-2015.pdf

Using Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) data, a method, dubbed the "variance method", is developed for retrieving nighttime aerosol optical thickness (&tau;) values through the examination of the dispersion of radiance values above an artificial light source. Based on the improvement of a previous algorithm, this updated method derives a semi-quantitative indicator of nighttime &tau; using artificial light sources. Nighttime &tau; retrievals from the newly developed method are inter-compared with an interpolated value from late afternoon and early morning ground observations from four AErosol RObotic NETwork (AERONET) sites as well as column-integrated &tau; from one High Spectral Resolution Lidar (HSRL) site at Huntsville, AL, during the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC⁴RS) campaign, providing full diel coverage. Sensitivity studies are performed to examine the effects of lunar illumination on VIIRS &tau; retrievals made via the variance method, revealing that lunar contamination may have a smaller impact than previously thought; however, the small sample size of this study limits the conclusiveness thus far. VIIRS &tau; retrievals yield a coefficient of determination (<i>r</i>²) of 0.60 and a root-mean-squared error (RMSE) of 0.18 when compared against straddling daytime-averaged AERONET &tau; values. Preliminary results suggest that artificial light sources can be used for estimating regional and global nighttime aerosol distributions in the future.