A Study toward an Improved Understanding of the Relationship between Visible and Shortwave Measurements

Abstract

Narrowband (NB) to broadband (BB) conversion is a common practice to acquire radiation budget data from operational imagery data. This study attempts to gain further insights into the relationship between NB visible (VIS) albedo and BB shortwave (SW) albedo by means of observational analysis and radiative transfer modeling. Multiple observation datasets were employed including Scanner for Radiation Budget (ScaRaB) satellite measurements, National Centers for Environmental Prediction?National Center for Atmospheric Research reanalysis of precipitable water and temperature profiles, Total Ozone Mapping Spectrometer ozone amount, etc. Radiative transfer modeling was done with an adding?doubling model of high spectral resolution for a range of surface, atmospheric, and cloud conditions. ScaRaB provided calibrated synergistic measurements of VIS and SW albedos. The two types of albedos were found to be linearly correlated with much higher correlation coefficients than previously obtained from other instruments. In combination with other datasets, the impact of various parameters on the VIS?SW relation was investigated and compared with the results of modeling. The most significant parameter influencing the relation is the solar zenith angle, followed by cloud-top height, precipitable water amount, ozone amount, aerosol, and cloud microphysics. Narrow- to broadband conversion models with a varying number of input parameters were developed and validated.