1. a Institute of Geodesy and Photogrammetry , Swiss Federal Institute of Technology ETH , ETH‐Hoenggerberg , 8093 Zürich, Switzerland
2. b Federal Ortice of Meteorology and Climatology MeteoSwiss , Kraehbuehlstrasse 58, 8044 Zürich, Switzerland
3. c Scripps Institution of Oceanography (SIO) , University of California , San Diego (UCSD) , 9500 Gilman Dr., La Jolla, California 92093‐0701, USA
4. d German Weather Service (DWD) , Meteorological Observatory Lindenberg , Am Observatorium 12, 15848 Lindenberg, Germany