Validation of the Two-Layer Model for Correcting Clear Sky Reflectance Enhancement Near Clouds

The retrieval of aerosol properties near clouds from reflected sunlight is challenging. Sunlight reflected from clouds can effectively enhance the reflectance in nearby clear regions. Ignoring cloud 3D radiative effects can lead to large biases in aerosol retrievals, risking an incorrect interpretation of satellite observations for aerosol-cloud interaction. Earlier, we developed a simple two-layer model to compute the cloud-induced clear-sky radiance enhancement that is due to radiative interaction between boundary-layer clouds and the molecular layer above. In the two-layer model, the 3D cloud induced enhancement is a function of upward flux in the cloud field and molecular optical depth above clouds. Though the two-layer model is simple and promising, it is rather challenging to validate it through direct observation because of the complex nature of aerosol/cloud system.

Here we use SHDOM and LES simulated reflectance as “truth” to validate the two-layer model. We compare the reflectance enhancement estimated form the two-layer model with the “truth” from the SHDOM simulation for wavelength 0.47 μm. We find that the two-layer modeled enhancement agrees reasonably well with the “truth”.