Spectroscopic database for TROPOMI/Sentinel 5 precursor

Abstract

The ESA project „SEOM-Improved Atmospheric Spectroscopy Databases (IAS)“ will improve the spectroscopic database for retrieval of the data products CO, CH4, O3 and SO2 column amounts measured by the TROPOMI instrument (TROPospheric Monitoring Instrument) aboard the Sentinel 5 precursor. The project was launched in February 2014 with 3 years duration. The spectroscopy of CO, CH4 and O3 in the 2.3 µm region is covered in the first 2 years, while UV measurements of SO2 and UV/FIR/IR measurements of ozone will be carried out in the last year. User requirements for the spectroscopic database were obtained by retrieval simulations, indicating the need to take line mixing into account in case of CH4, to measure HDO in case of water and even to measure line broadening of CH4 lines by water vapor. A dedicated line model will be used to represent the laboratory spectra since the Voigt routine was found to be not sufficient to obtain the needed accuracy. Details on the retrieval simulations will be given together with the user requirements and the laboratory measurement plan. Measurements of pure water and ambient temperature air broadened measurements of water were finalized in March 2015 utilizing a high resolution Bruker IFS 125HR Fourier-Transform spectrometer at DLR. Complementary, continuous wave cavity ring-down measurements of pure water were also finalized in Grenoble, France. First quality checks and intercomparison of the data will be shown. Furthermore, the latest laboratory results will be presented.