I am combining numerical models and observations to provide a 4D picture of tropospheric constituents with error quantification, in order to address fundamental questions about Air Quality and the Carbon Cycle. My research experience includes the development and the diagnostic of data assimilation chains within global and regional scale chemistry-transport models. I am using a wide range of observations from networks of surface in-situ measurements, field campaign experiments, ground based and satellite remote sensing instruments, including the assessment of future satellite missions.