An operational procedure for precipitable and cloud liquid water estimate in non-raining conditions over sea: study on the assessment of the nonlinear Physical Inversion algorithm

In a previous work, an operative procedure to estimate precipitable and liquid water in non-raining conditions over sea was developed and assessed. The procedure is based on a fast non-linear physical inversion scheme and a forward model; it is valid for most of satellite microwave radiometers and it also estimates water effective profiles. This paper presents two improvements of the procedure: first, a refinement to provide modularity of the software components and portability across different computation system architectures; second, the adoption of the CERN MINUIT minimisation package, which addresses the problem of global minimisation but is computationally more demanding. Together with the increased computational performance that allowed to impose stricter requirements on the quality of fit, these refinements improved fitting precision and reliability, and allowed to relax the requirements on the initial guesses for the model parameters. The re-analysis of the same data-set considered in the previous papers showed an improvement of the consistency of the estimates from SSM/I and TMI radiometers and of the agreement with the statistical references. The described work confirmed the stability of the overall approach of the operative Procedure and prepared for new satellite generations (e.g. AMSR-E).