Speaker
Description
The σ-FORUM is a fast radiative transfer code designed to calculate the Earth’s spectrum radiance in the infrared range and the associated Jacobian matrices. Primarily developed by the University of Basilicata for the IASI (Infrared Atmospheric Sounder Interferometer) instrument, it has recently been extended to deal with clouds presence and cover a wider spectral interval that includes the far infrared band observed by FORUM (Far-Infrared Outgoing Radiation Understanding and Monitoring). The σ model spans the spectral range of 5 to 3000 cm-1 and it uses a fixed pressure grid containing 60 levels that extend from the ground level to the top of the atmosphere. The code parameterizes gas optical depths as a low-order polynomial of temperature. For water vapor, it uses a different approach to account for gas concentration effects like self-broadening of spectral lines. The radiance calculations in cloudy sky conditions are based on an implementation of the scaling method that allows for multiple scattering effects.
As part of the FIT-FORUM project, the code has been completely reengineered compared to the previous σ version. Structural changes have been made to the management of internal operations, along with the addition of new functionalities. Tools have also been introduced to improve the interface and implement error handling, which was absent in the original version. Several new user-selectable features have been added.
