Rinus Scheele was educated the HTS Enschede (Fysische Techniek) and started working at the KNMI in 1984 as assistant researcher. He developed and used TRAJKS, a trajectory model that was used for backwards and forward calculations of the path of air parcels. He contributed to several campaigns in measuring air pollution, like INDOEX, CARIBIC and a lot of smaller campaigns. TRAJKS is used both to forecast to help optimize observations and using analysis, to help analyze observed tracers. For example TRAJKS was used to monitor the volcanic ashes exhaust of the Eyjafjöllajokull in April 2010 and the Grimsvötn in May 2011. Beside these episodic studies TRAJKS was used to analyze the quality of numerical weather prediction. For example studies were done to the age of air, to get an idea of the quality of the modeled transport through the tropopause.