The selection of FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) as the ninth ESA Earth Explorer mission (ESA, 2019), planned for launch in the 2026 timeframe, offers a unique opportunity for advancing our capability to observe and model the outgoing terrestrial component of the Earth Radiation Budget. The MIR-FIR (Middle InfraRed - Far-InfraRed) Fourier Transform spectrometer of the FORUM payload will perform nadir-looking measurements of the Earth's emission spectrum at the top of the atmosphere from 100 to 1600 cm-1 with a resolution better than 0.50 cm-1 from sun-synchronous orbit. FORUM observations, especially in the spectral range of 100-667 cm-1, will fill the existing gap of systematic spectrally resolved observations on a global scale of the Earth's emitted radiance in the far-infrared. A major impact is expected from the availability of these observational data due to the contribution of far-infrared wavelengths to atmospheric and surface emission, and thus to the energy budget of the planet. In clear sky, at least one quarter of the Earth's greenhouse effect is associated with radiative processes occurring in the far-infrared, whilst the region contributes more than half the outgoing energy radiated globally to space in all-sky conditions (up to 60% in polar regions), as the colder temperatures of high altitude clouds shift the peak of the emission to longer wavelengths. Moreover, significant improvements in the estimate of OLR (Outgoing Longwave Radiation) fluxes in clear sky conditions can be derived from far-infrared measurements of surface emission in the polar regions. Here, we report the outcome of a survey conducted, as part of the ESA project "FORUM: Consolidation of Requirements and Reference Scenarios", to evaluate the innovative impact of the mission related to atmospheric and surface variables and to cloud products, focusing in particular on the estimate of OLR fluxes. The survey has covered a comprehensive set of previous and on-going missions devoted to monitoring the Earth radiation budget, highlighting the potential of the spectrally resolved observations of FORUM to disentangle different forcing mechanisms contributing to the OLR in comparison to integrated broadband measurements. Results will be also presented of the analysis of prospective synergies with concurrent missions, such as MetOp Second Generation. FORUM will fly in loose formation with MetOp-SG/A to exploit as a first priority the complementary information of IASI-NG. However, added value may also be derived from the synergy with METimage (and 3MI) through the development of dedicated angular distribution models and/or more accurate characterization of the anisotropy of FORUM scenes. Finally, we provide results from a user survey highlighting the main applications that a FORUM flux product could benefit, and the desired product characteristics in each case.
The FORUM mission: synergy and comparison with other instruments for the estimate of the OLR fluxes
U Cortesi;P Raspollini;M Ridolfi;S Della Fera;G Poli;C Belotti;L Palchetti;
2020
Abstract
The selection of FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) as the ninth ESA Earth Explorer mission (ESA, 2019), planned for launch in the 2026 timeframe, offers a unique opportunity for advancing our capability to observe and model the outgoing terrestrial component of the Earth Radiation Budget. The MIR-FIR (Middle InfraRed - Far-InfraRed) Fourier Transform spectrometer of the FORUM payload will perform nadir-looking measurements of the Earth's emission spectrum at the top of the atmosphere from 100 to 1600 cm-1 with a resolution better than 0.50 cm-1 from sun-synchronous orbit. FORUM observations, especially in the spectral range of 100-667 cm-1, will fill the existing gap of systematic spectrally resolved observations on a global scale of the Earth's emitted radiance in the far-infrared. A major impact is expected from the availability of these observational data due to the contribution of far-infrared wavelengths to atmospheric and surface emission, and thus to the energy budget of the planet. In clear sky, at least one quarter of the Earth's greenhouse effect is associated with radiative processes occurring in the far-infrared, whilst the region contributes more than half the outgoing energy radiated globally to space in all-sky conditions (up to 60% in polar regions), as the colder temperatures of high altitude clouds shift the peak of the emission to longer wavelengths. Moreover, significant improvements in the estimate of OLR (Outgoing Longwave Radiation) fluxes in clear sky conditions can be derived from far-infrared measurements of surface emission in the polar regions. Here, we report the outcome of a survey conducted, as part of the ESA project "FORUM: Consolidation of Requirements and Reference Scenarios", to evaluate the innovative impact of the mission related to atmospheric and surface variables and to cloud products, focusing in particular on the estimate of OLR fluxes. The survey has covered a comprehensive set of previous and on-going missions devoted to monitoring the Earth radiation budget, highlighting the potential of the spectrally resolved observations of FORUM to disentangle different forcing mechanisms contributing to the OLR in comparison to integrated broadband measurements. Results will be also presented of the analysis of prospective synergies with concurrent missions, such as MetOp Second Generation. FORUM will fly in loose formation with MetOp-SG/A to exploit as a first priority the complementary information of IASI-NG. However, added value may also be derived from the synergy with METimage (and 3MI) through the development of dedicated angular distribution models and/or more accurate characterization of the anisotropy of FORUM scenes. Finally, we provide results from a user survey highlighting the main applications that a FORUM flux product could benefit, and the desired product characteristics in each case.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
