Quantifying Relationship between Cloud Radiative Forcing, Cloud fraction and Cloud Albedo, and Their Multiscale Variations

Cloud radiative forcing, cloud fraction, and cloud albedo have been widely used in study of cloud influences on radiation budget; however, their mutual relationship and multiscale variations have not been well understood and quantified. Here a new analytical relationship between the three quantities is first formulated. The analytical expression is further applied to derive, for the first time, long-term, high-resolution time series of cloud albedo by using concurrent surface-based measurements of downwelling surface shortwave radiation and cloud fraction collected by the US Department of Energy's Atmospheric Radiation Measurement (ARM) Program at the ARM Great Southern Plains (SGP) site since 1997. The time series of normalized shortwave radiative forcing, cloud fraction and cloud albedo are then examined for their multiscale (diurnal, annual and inter-annual) variations and covariations. The results show that all the three quantities exhibit strong diurnal and annual cycles but less interannual variability. Comparison with independent measurements from satellites will be explored.