• marine stratocumulus;
  • remote sensing;
  • cloud properties

[1] Collocated Moderate Resolution Imaging Spectroradiometer (MODIS) imagery and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) 532 nm total attenuated backscatter coefficients were used to identify 50 km scale segments for ocean regions that had only a single layer of marine stratocumulus. On the basis of whether the underlying ocean surface was detected in the backscatter coefficients, the segments were separated into those for which all of the 1 km MODIS pixels were identified as being overcast (no surface detected) and those for which there were breaks in the cloud layer (surface detected). Cloud properties for the collocated MODIS pixels were obtained from the MODIS MOD06 cloud product and from a retrieval scheme designed to account for broken clouds within imager pixels. For the 50 km overcast segments the variations in optical depth, τ, and droplet effective radius, Re, obtained from the MOD06 and partly cloudy pixel retrievals were in agreement, and the variations in layer temperature were consistent with those inferred from the CALIPSO backscatter coefficients. In addition, the droplet effective radii retrieved separately using the 1.6, 2.1, and 3.7 μm MODIS reflectances were consistent with droplets growing as clouds thickened and mean values of dlnRe/dlnτ were close to 0.2, as predicted by adiabatic cloud parcel models. When the segments contained broken clouds, however, the droplet effective radii for the three near-infrared wavelengths were inconsistent with droplets growing as clouds thickened and dlnRe/dlnτ departed from 0.2. This breakdown is thought to result from biases in the retrieved cloud properties caused by subpixel-scale variations in liquid water amount and droplet radius.