In addition to standard products, the multidirectional polarization measurements of POLDER make it possible to estimate the Cloud Droplet Radius for liquid phase clouds. The method is very accurate, but it applies to specific conditions only. The monthly mean values are shown here. Some regions are white because they do not include extended liquid cloud fields that are necessary to apply the retrieval method.
The monthly mean map clearly shows the well-known bias between oceanic and continental regions (smaller droplets over land surfaces). The smallest droplets are observed in regions affected by anthropogenic pollution or biomass burning.
These retrievals were used to quantify the relationship between aerosol load and cloud droplet radius, the first step of the so-called aerosol indirect effect (Bréon et al. Science, 2002).

June 1997

 

June 2003