An OSSE to Quantify the Impact of S5 Spaceborne Carbon Monoxide Total Column Measurements on Air Pollution Analysis and Forecast over Europe

In the framework of ISOTROP project (Impact of Spaceborne Observations on Tropospheric Composition Analysis and Forecast) aiming to assess the impact of sentinel 4 (GEO) and 5 (LEO) measurements of O3, CO, NO2 and HCHO to better constrain pollutant concentrations and precursor emissions that influence air quality. A Regional-scale Observing System Simulattion Experiment (OSSE ) has been conducted over Europe to determine the impact of S5-precursor carbon monoxide total column future observations on tropospheric composition forecasting and analysis. This OSSE study involves two independant CTM models which is a considerable advantage for the study, since it guarantees that the OSSE results will not be overly optimistic results and the OSSE will more realistically simulate an assimilation of real observations. The nature run which consitute the true composition atmospheric state is simulated by LOTOS-EUROS model combined with the global TM5 chemistry-transport model. The synthetic S5-p CO total column measurements and their error characterisitcs are derived from the nature run data and generated by KNMI and FMI teams using a state-of-the-art retrieval algorithm involved in TROPOMI development. The control run in which we assimilate the CO measurements is MOCAGE model. Interestingly, the OSSE results show substantial benefit from CO data assimilation especially in the boundary layer on both the forecast and analysis, and demenstrated that a high-spatial resolution and high-quality measurements of S5 CO total column could potentially constrain the concentration in the atmospheric boundar layer.