Polarization measurements from the spaceborne POLDER instrument are used to estimate the droplet effective radius of liquid-phase clouds. Eight months of measurements have been processed. Seasonal averages have been generated and are discussed here. The measurements confirm that, on average, droplets are 2 to 3 &mgr;m smaller over land than over the oceans. The smaller droplets are found over highly polluted regions and in areas affected by smoke from biomass burning activity. The influence of land masses is apparent downwind of the continents. Largest droplets are found in remote tropical oceans, away from major aerosol sources. A large zonal gradient is also apparent in the southern oceans, with very small droplets close to the Antarctic continent. ¿ 2000 American Geophysical Union