A nested application of four-dimensional variational assimilation of tropospheric chemical data

The chemistry transport model system EURAD-IM and its variational data assimilation module are applied to assess air quality conditions during the measurement campaign VERTIKO. The inverse modelling system has been designed to run in a nested setup, assimilating in-situ observations and measurements by remote sensing. The benefits of joint initial value and emission rate optimisation are emphasised, significantly enhancing analysis skill for air quality related constituents including ammonia and benzene.