Pieternel Levelt¹, Joanna Joiner², Johanna Tamminen³, Pepijn Veefkind⁴, Pawan K Bhartia⁵, Deborah C Stein⁴, Bryan N Duncan², Henk Eskes⁴, Ronald van der A⁴ and Sergey V Marchenko⁶, (1)Royal Netherlands Meteorological Institute, De Bilt, 3730, Netherlands, (2)NASA GSFC, Greenbelt, MD, United States, (3)Finnish Meteorological Inst., Helsinki, Finland, (4)Royal Netherlands Meteorological Institute, De Bilt, Netherlands, (5)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (6)SSAI, Lanham, MD, United States