The ring effect in the cloudy atmosphere

Filling-in of spectral features observed in scat- tered sunlight and known as the \Ring Eect" has a sig- nicant impact on the retrieval of atmospheric trace con- stituentsfrombothground-basedandsatelliteobservations. As clouds also have strong impacts on radiative transfer in the UV/visible spectral range, possible changes of the Ring Eect due to clouds have to be considered. Such investiga- tions require radiative transfer modeling explicitly account- ing for both cloud and Ring features. UV/visible ground and satellite based measurements, taken under cloudy con- ditions, were used to validate Ring and cloud modeling us- ingtheradiativetransfermodelSCIATRAN.Asanexample results of model applications are presentedfor bothground- based and satellite geometry. Two case studies are used to explain the sources of the observed Filling-in.