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

[摘要] Using Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB)data, a method, dubbed the "variance method", is developed for retrievingnighttime aerosol optical thickness (τ) values through the examinationof the dispersion of radiance values above an artificial light source. Basedon the improvement of a previous algorithm, this updated method derives asemi-quantitative indicator of nighttime τ using artificial lightsources. Nighttime τ retrievals from the newly developed method areinter-compared with an interpolated value from late afternoon and earlymorning ground observations from four AErosol RObotic NETwork (AERONET)sites as well as column-integrated τ from one High Spectral ResolutionLidar (HSRL) site at Huntsville, AL, during the NASA Studies of Emissions andAtmospheric Composition, Clouds and Climate Coupling by Regional Surveys(SEAC⁴RS) campaign, providing full diel coverage. Sensitivity studiesare performed to examine the effects of lunar illumination on VIIRS τretrievals made via the variance method, revealing that lunar contaminationmay have a smaller impact than previously thought; however, the small samplesize of this study limits the conclusiveness thus far. VIIRS τretrievals yield a coefficient of determination (r²) of 0.60 and aroot-mean-squared error (RMSE) of 0.18 when compared against straddlingdaytime-averaged AERONET τ values. Preliminary results suggest thatartificial light sources can be used for estimating regional and globalnighttime aerosol distributions in the future.

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