Clouds cover about 70% of the Earth's surface and play a dominant role in the energy and water cycle of our planet. Only satellite observations provide a continuous survey of the atmospheric state over the entire globe. Satellite cloud data records now exceed more than 25 years; however, climatologies compiled from different satellite datasets can exhibit systematic biases.
The Global Energy and Water cycle Experiment (GEWEX) Cloud Assessment, initiated in 2005 by the GEWEX Radiation Panel and finalized in 2012, provides the first coordinated intercomparison of publically available, global cloud products (gridded, monthly statistics) retrieved from measurements of multi-spectral imagers, IR sounders, and lidar.