The sensitivity of the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission to dust aerosols: a pseudo-observations analysis

Abstract. The Earth Explorer 9 Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission will bring the first satellite instrument capable of observing the Earth's far infrared (FIR) spectra with a high spectral resolution. Using an ad-hoc pseudo-observations (PO) simulator, we generate FORUM PO that we use to evaluate its sensitivity to dust aerosols. We compare the sensitivity of the FIR (15–100 µm) part of the spectra to that of the mid infrared (MIR, 2.5–15 µm) as observed by the Infrared Atmospheric Sounder Interferometer – New Generation (IASI-NG) instrument. Different dust scenarios are tested, in terms of mineralogy, source region and background atmosphere, burden and vertical distribution. The simulations in this study show a clear FIR spectral signature of dust in the Earth's atmosphere, and a corresponding dust sensitivity in the FIR spectra. The analysis of spectral signatures and Jacobians suggests that the FORUM observations are expected to bring an added value to dust observations from satellite, with respect to MIR-only, especially in cases of large burdens of mid-to-long-range transported plumes of dust in the free and upper troposphere. At these conditions, the FIR contributes up to the 50 % of the overall infrared sensitivity, and the impact of interfering species, like water vapour, is limited. More quantitative estimations of the inherent information content are needed to corroborate our results.