JURASSIC (Inverse radiance modeling)
The analysis of limb and nadir sounders in the infrared region is an inverse problem. It requires an accurate radiation transport model and associated inversion procedures. JURASSIC is a software package developed by IEK-7 for analysing the measured data from instruments of this type.
The new version of the software, JURASSIC2, is being developed further by several PhD students and postdocs at the institute. JURASSIC2 is used in retrieval studies for the (tomographic) derivation of 3D trace gas distributions from PREMIER and GLORIA data. At the moment, CRISTA-NF measurements from the RECONCILE campaign are also being analysed with JURASSIC2.
JURASSIC2 is based on Python/C++ and additionally contains a generic instrument model, which is able to accurately simulate the field of vision and correlated instrument effects, even for different instruments in the same analysis. Linear algebra can use sparse matrices and associated algorithms, which means considerable advantages, in particular for 2D and 3D tomographical analysis. In addition to Bayesian estimation, Tikhonov regularization is also used with different norms. In cooperation with STCE der RWTH Aachen, IEK-7 is working on an analytical derivation using algorithmic differentiation, which can already calculate the derivative matrices when the model is simulated, causing little extra cost. This reduces the typical computing time required for an inversion by one to three orders of magnitude, depending on the problem size.