A230-0008
The FORUM mission: synergy and comparison with other instruments for the estimate of the OLR fluxes

Wednesday, 16 December 2020
Poster
Ugo Cortesi1, Piera Raspollini2, Marco Ridolfi3, Stefano Della Fera1,4, Gabriele Poli1, Claudio Belotti5, Luca Palchetti6, Helen E Brindley7 and Richard J Bantges7, (1)Istituto di Fisica Applicata “Carrara” - Consiglio Nazionale delle Ricerche (IFAC-CNR), Sesto Fiorentino, Italy, (2)Institute of Applied Physics "Nello Carrara'' - National Research Center of Italy, Sesto Fiorentino, Italy, (3)Istituto Nazionale di Ottica - Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy, (4)Università di Bologna, Dipartimento di Fisica e di Astronomia, Bologna, Italy, (5)CNR-INO National Institute of Optics, Florence, Italy, (6)Istituto Nazionale di Ottica - Consiglio Nazionale delle Ricerche (INO-CNR), Sesto Fiorentino, Italy, (7)Space and Atmospheric Physics Group, Imperial College London, London, United Kingdom
Abstract:
The selection of FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) as the ninth ESA Earth Explorer mission, planned for launch in 2026, 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 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 range 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 FIR.

A major impact is expected from these observational data due to the contribution of FIR 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 in the FIR, and the region contributes more than half the outgoing energy radiated globally to space in all-sky conditions, 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 can be derived from FIR measurements of surface emission in the polar regions.

We report the outcome of a survey conducted for the ESA project “FORUM: Consolidation of Requirements and Reference Scenarios”, to evaluate the innovative impact of the mission, in particular on the estimate of OLR fluxes. The survey has covered a comprehensive set of previous and ongoing 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.

We present prospective synergies with concurrent missions, such as MetOp-SG/A for the complementary information of IASI-NG, as well as of METImage and 3MI. 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.

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