Impact of gas absorption and surface albedo on cloud radiative smoothing

Abstract

Using visible and near infrared aircraft observations of stratocumulus clouds over land, the impact of gas absorption and surface albedo on cloud radiative smoothing has been studied. Time series of the observed nadir radiances have been converted into Fourier space, and the scale break as well as the large scale and small scale slopes of the resulting spatial power spectrum have been analyzed. An increase in gas absorption leads to a reduction in radiative smoothing due to a decreased likelihood of horizontal photon transport within the cloud. This can be seen both in the derived scale breaks and in the slope of the power spectrum at high spatial wavenumbers which exhibit a high correlation with cloud single scatter albedo. An increase in surface albedo leads to a radiative smoothing of the observed radiance field at scales proportional to the cloud height and to a decrease in the slope of the large scale spatial power spectrum.