The ECMWF 1D-Var package is a generalised minimisation code applicable to a wide range of inversion problems for satellite data, and it is not set up to handle any particular instrument. It makes use of the M1QN3 software from INRIA (quasi-Newton method) and preconditions the state vector with the eigenvectors of the background error covariance. The code is in Fortran and documented. It cannot be treated as a ‘black box’ as various additional modules have to be interfaced to the ECMWF 1D-Var package before it will work. The user must define a control variable and interface an appropriate radiative transfer model, though an example (for retrieval of cloud parameters) is supplied with the package.
Version 2 was released in November 2004.
Brief outline of plans
- Undertake maintenance as necessary.
- Further developments depend on user-requirements and other NWP SAF priorities.