A230-0001
The potential contribution of FORUM mission to the evaluation and improvement of OLR fluxes estimation in EC-Earth climate model

Wednesday, 16 December 2020
Poster
Stefano Della Fera1,2, Ugo Cortesi2, Piera Raspollini2, Marco Ridolfi3, Jost von Hardenberg4,5 and Federico Fabiano6, (1)Università di Bologna, Dipartimento di Fisica e di Astronomia, Bologna, Italy, (2)Istituto di Fisica Applicata “Carrara” - Consiglio Nazionale delle Ricerche (IFAC-CNR), Sesto Fiorentino, Italy, (3)Istituto Nazionale di Ottica - Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy, (4)Politecnico di Torino, Dipartimento di Ingegneria dell'Ambiente, del Territorio e delle Infrastrutture, Torino, Italy, (5)Istituto Nazionale di scienze dell’atmosfera e del clima-Consiglio Nazionale delle Ricerche (ISAC-CNR), Torino, Italy, (6)Istituto Nazionale di scienze dell’atmosfera e del clima-Consiglio Nazionale delle Ricerche (ISAC-CNR), Bologna, Italy
Abstract:
Earth’s emitted energy in the wavelength range from 4 to 100 μm is commonly termed Outgoing Longwave radiation (OLR) and its accurate measurement is a first-priority requirement to assess the energy balance of the planet. Integrated broadband OLR fluxes provided by CERES dataset constitutes the standard reference to study the Earth’s energy budget and represents the target values of energy fluxes at top of atmosphere (TOA) for climate models tuning. Even if tuning operations guarantee a good agreement on a global basis between observed and simulated OLR at TOA, large regional biases occur all over the globe and a significant spread exists between different climate model simulations.

The Far-Infrared Outgoing Radiation and Monitoring (FORUM) mission, planned for launch in 2026, will provide nadir-looking spectrally resolved radiance measurements of the Earth’s emission spectrum at TOA from 100 to 1600 cm-1 with a resolution better than 0.50 cm-1. For the first time FORUM measurements will fill the observational gap in the Far-InfraRed (FIR) range from 100 to 667 cm-1 providing spectrally resolved OLR fluxes (level 2 data product).

In anticipation of FORUM measurements, we want to quantify the potential improvement of climate models in simulating OLR fluxes at TOA due to the future availability of spectrally resolved fluxes data from FORUM, extending to the FIR. At this stage, we focus on the analyses of simulations provided by EC-Earth (version 3.3.2), a new climate model developed by the joint effort of 27 research institutes of 10 European countries which has directly contributed to Coupled Model Intercomparison (CMIP) in its phases 5 and 6.

Atmospheric profiles and information on the surface and on the clouds produced by EC-Earth simulations in simplified conditions are provided in input to SIGMA-IASI, a radiative transfer model able to calculate spectral radiances compatible with those that will be measured by FORUM. From these synthetic measurements, we estimate OLR fluxes by applying angular distribution models (ADM) of increasing complexity. The comparison between the OLR fluxes provided by the EC-Earth simulation and those calculated from synthetic FORUM measurements may allow to identify potential improvements for the parametric radiative module included in EC-Earth to estimate the OLR radiative fluxes.

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