1. Royal Observatory of Belgium; Brussels Belgium
2. Institute for Atmospheric and Climate Science; ETH Zurich; Zurich Switzerland
3. Physikalisch-Meteorologisches Observatorium Davos; World Radiation Center; Davos Dorf Switzerland
4. Université Paris Saclay, Université Paris VI-Pierre et Marie Curie, CNRS/INSU, LATMOS-IPSL; Guyancourt France