On November 17th we received the sad news that Jan Kretzschmar passed away on Sunday,15th November 2020.

Jan was one of the co-founders of the Harmo Initiative and organized the 3rd and 4th Harmonization conferences in Mol (1994) and Oostende (1996) respectively. He began his career at SCK, Study Centre for Nuclear Energy in Mol, where he started in 1972 in non-nuclear environmental research. That was the start of the development of the IFDM model and of the many applications of Gaussian modelling in projects in Flanders and abroad.

Jan has worked at VITO from the beginning in 1991 until 2007 as department head and research director of energy, materials and environmental technology at VITO. From 2005 to 2014 Jan was part-time professor at the University of Antwerp in the Department of Bioscience Engineering, where he taught energy and environmental technology. He became a member of the Royal Flemish Academy of Belgium for Science and the Arts in 2009.

We are grateful for his legacy in air quality modelling and in particular his international contributions and efforts to put forward the Harmonization initiative. Back in the 70's he laid the foundation for Gaussian modelling and for assessing and tackling air quality problems in Flanders. Many of us here at VITO still continue that work. I often received mails from Jan telling me how proud and thankful he was for what we realized together over the past 50 years.