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Seminar

Title : Using TES and IASI satellite observations to test climate model predictions of ozone radiative forcing
Name of the speaker : Helen Worden
Affiliation : National Center for Atmospheric Research (NCAR), Boulder, CO, USA
Laboratory organizer : LATMOS
Date and time : 10-06-2014 11h00
Location : UPMC - LATMOS - Tour 45-46, 4e étage - salle des séminaires
Summary :

Recent international assessments have demonstrated the co-benefits ofcontrolling tropospheric ozone for both near-term climate change and airquality. However, strategies for targeting ozone precursor emissions requireaccurate model predictions of ozone radiative forcing (RF). Troposphericozone has the third highest RF for anthropogenic greenhouse gases sincepre-industrial times, but high uncertainties and a large spread in modelvalues remain in the IPCC AR5. We will show how TES observations of ozoneand the sensitivity of TOA (Top Of Atmosphere) radiative flux to ozone havebeen used to reduce the uncertainty in the mean estimate of troposphericozone RF from the ACCMIP (Atmospheric Chemistry and Climate ModelIntercomparison Project) reported in the IPCC AR5. We also present theresults of combining TES TOA flux sensitivity and the GEOS-chem adjoint todetermine the radiative effect of ozone precursor emissions NOx, CO and NMHC(non-methane hydrocarbons). This study showed a large spatial dependence forradiative forcing from ozone as a function of where the precursors wereemitted. For example, NOx emissions from Chicago have to be more than 3times larger than Atlanta emissions to have the same forcing. These previousTES results provide motivation for new work to benchmark themodel-to-satellite differences in TOA ozone band flux and flux sensitivity.The TOA flux for the infrared ozone band is a fundamental quantity which ispredicted by IPCC chemistry-climate models but never tested directly againstsatellite measurements. The continuation of the TES record of infrared ozonespectra with long-term IASI data will allow accurate predictions of futureozone forcing and an assessment of the feedback from changes in thehydrological cycle on ozone RF.