Eleni Marinou, National Observatory of Athens (NOA), Greece; Holger Baars, Leibniz Institute for Tropospheric Research (TROPOS), Germany; Lucia Mona, Consiglio Nazionale delle Ricerche (CNR), Italy; Ewan O'Connor, Finnish Meteorological Institute (FMI), Finland; Stephanie Rusli, Rob Koopman, European Space Agency (ESA), Netherlands; Ann Mari Fjæraa, Climate and Environmental Research Institute NILU, Norway; Doina Nicolae, National Institute of Research and Development for Optoelectronics - INOE 2000, Romania