Vertical structure of stratiform marine boundary layer clouds and its impact on cloud albedo

One year of passive microwave as well as near infrared remote sensing observations of cloud liquid water path (LWP) are used to study stratiform marine boundary layer clouds on a large scale. Good agreement between the two different remote sensing estimates of LWP was found for values below 150 g/m(2), if the clouds were assumed to be stratified vertically. For higher values of LWP the near infrared observations show a lower LWP than the passive microwave observations. Theoretical calculations of cloud albedo suggest a potentially significant underestimation of cloud albedo if, for a given LWP, clouds are assumed to be vertically homogeneous. The results presented in this study bear significance especially for climate studies. Of particular relevance is the conclusion that also at the large scale marine boundary layer clouds need to be regarded as being vertically adiabatically or sub-adiabatically stratified.