Validation studies with and 3D radiative transfer in surrogate cloud fields

It is (currently) not possible to measure the properties of a cloud field in all 3 dimensions at a sufficient spatial and temporal resolution for radiative transfer (RT) studies. It is however possible, to estimate the statistical properties of a cloud field from limited measurements and to reconstruct a full 3D cloud field which has these measured properties.

We have developed three such generators (IAAFT, CLABAUTAIR, and SITCOM) and initialised them with aircraft measurements (overcast stratocumulus and broken cumulus). Afterward comparisons between irradiances calculated with a 3D Monte Carlo RT code using the surrogate fields and the radiative measurements are employed to asses the reconstruction process.

Next to airplane data, we have used liquid water content profiles from ground-based remote sensing data to generate cloud fields with the IAAFT algorithm. These 2D measurements and 3D fields were used to study the differences between RT in 2D cross cuts and full 3D cloud fields.