In this presentation we report on the impact of a more realistic low-cloud cover parameterization on the Sea Surface Temperature (SST) predicted by an ocean-atmosphere coupled system. The cloud parameterization is based on concepts associated with probability density functions (PDFs) of moist conserved variables. In particular, it is shown that the global atmospheric model with more realistic boundary layer clouds leads to a more realistic distribution of the SST in the ocean's tropics, subtropics and mid-latitudes. Typical SST biases of up to 5 C in regions under frequently observed stratus and stratocumulus are substantially reduced, to unbiased values at places. This represents a substantial SST forecast improvement in terms of global ocean-atmosphere coupled systems.