Global distribution of cloud top phase from POLDER/ADEOS I

The eight months of data acquired by the POLDER instrument have now been processed. This dataset provides daily information on the global distribution of cloud top phase. We present here the results of a statistical analysis of ice and liquid phase occurrence frequencies at the global scale. Temporal variation of these frequencies above land and ocean are analyzed. These results are compared with ISCCP data and the consistency of the POLDER phase product is demonstrated. formed in the upper cloud layer. Around 80% of the single scattered radiation reflected from the cloud layer arises from the top 100 m of the layer. Calculations have shown that the polarized component, Lp, is saturated for cloud optical depth greater than 2.0. The important quantity for determining cloud phase is the polarized radiance Lp, that is less sensitive than the total radiance x L to multiple scattering effects. Thus, the polarization features, which correspond to single scattering, are preserved in Lp.