4A/OP, a fast & accurate operational forward radiative transfer model.

4A/OP is a user-friendly radiative transfer model for various scientific applications, co-developed by NOVLETIS and Laboratoire de Meteorologie Dynamique, with the support of the French Space Agency.

4A/OP rely on line-by-line radiative transfer modelling for the computation of atmospheric transmittances, radiances and Jacobians, particularly efficient in terms of accuracy and computation time. It computes the optical thickness due to gaseous absorption for each atmospheric layer considered to be spherical. Its output is the radiance spectrum in a user-defined spectral domain in the infrared region.

4AO/OP is the reference radiative transfer model selected by CNES for several satellite missions: IASI, IASI-NG, MicroCarb et MERLIN. It is also used for other international satellite missions like GOSAT, SEVIRI… and for ground-based measurements (TCCON…).