An assessment of lunar photometry in AERONET

Abstract

AERONET has been acquiring direct beam lunar observations at six wavelengths from 440 to 1640 nm from most newer model T CIMEL sun-sky radiometers in the network for many years and producing a night-time AOD data set, which currently includes observations at 492 sites dating back as far as 2014. The new dataset of lunar AOD now uses an updated empirical correction for the ROLO lunar irradiance model and has been extensively analyzed for all long-term lunar-capable sites by evaluating the continuity of AOD between solar and lunar measurements during limited temporal windows. Comparison of daytime and nighttime AOD measurements shows good agreement at all sites with more than a decade of data with mean differences typically within ± 0.01 for AOD 440 nm and similar or better agreement at longer wavelengths. Comparisons during 3 h transition periods between day and night observations during conditions of low and stable AOD found statistically negligible differences of AOD at all common wavelengths as well as for Ångström Exponent, column water vapor and AOD fine and AOD coarse parameters from SDA. The lunar AOD product demonstrates consistency with solar AOD across diverse aerosol conditions at AERONET sites globally, validating the empirical correction approach.