Initial steps towards an inversion system for biogenic isoprene emissions in CAMS: Evaluation of IFS-COMPO formaldehyde simulations

We report on the analysis of formaldehyde (HCHO) simulations performed by the CAMS (Copernicus Atmosphere Monitoring Service) atmospheric composition forecasting system (IFS-COMPO) in different tropospheric regions, seasons, altitudes and air masses using a comprehensive data set of airborne measured HCHO vertical column densities and mixing ratios. The observations are derived from measurements of the HALO mini-DOAS instrument operated from aboard the German research aircraft DLR HALO during six international research missions in the years 2017 to 2019 and TROPOMI S5P satellite observations. In addition, measurements over the South American tropical rain forest in 2014 are included, as this region is of particular interest in the analysis of global biogenic emissions. In particular, the presented analysis evaluates HCHO in biogenic air masses and the impact of recent advances of biogenic emission estimation in IFS-COMPO on simulated biogenic VOCs. For this purpose, we evaluate operational IFS-COMPO HCHO simulations, which apply a climatology of monthly averaged biogenic emissions (Cams-Glob-BioV3.1), and HCHO simulations based on a recently developed online biogenic emission estimation module.

The above findings are part of the ongoing research carried out in the Horizon Europe CAMEO (CAMS EvOlution) project, which aims to develop an inversion of biogenic emissions within ECMWF’s Integrated Forecasting System. As a first step towards a successful implementation of HCHO assimilation and inversion capability within the IFS, a tangent linear and adjoint have been derived based on a simplified, linearized HCHO chemistry scheme. The impact of the assimilation of HCHO in IFS-COMPO is currently analyzed using TROPOMI S5P formaldehyde observations, with a particular focus on its impact on other atmospheric reactive trace gases, such as isoprene and ozone, and on aerosols.