Ozone instantaneous longwave radiative effect from IASI and TES observations
Résumé
Ozone is one of the most important greenhouse gases in terms of radiative forcing as a result of
increases in its precursor emissions since pre-industrial times. Until recently, the ozone radiative
forcing calculations were entirely model based, exhibiting high uncertainties and a large spread in
model values, as shown in the IPCC AR5. Satellite sounders operating in the infrared now offer the
possibility to infer directly the longwave radiative effect (LWRE) of ozone in the 9.6 μm band, with
respect to its vertical distribution, allowing to better constrain model estimates of the ozone radiative
forcing and its future predictions. In this presentation we calculate the ozone LWRE by exploiting the
measurements of IASI/MetOp-A. We briefly describe a new method for calculating the ozone LWRE
and the flux sensitivity with respect to the ozone profile, known as instantaneous radiative kernel
(IRK), and we demonstrate that it is more accurate than previous existing methods by up to 30%. We
also show a first comparison with similar quantities derived from measurements of TES/Aura and
report a very good agreement overall. Finally, we present the application of such calculation, made at
unprecedented resolution and sampling with IASI, in climate models and the ability of assessing the
biases of the latter in terms of radiative effect.