Advanced Infra-Red Water Vapour Estimator (AIRWAVE) algorithm version2

AIRWAVE (Advanced Infra-Red WAter Vapour Estimator) is an algorithm that has been expressly developed for the retrieval of TCWV from the measurements of the Along Track Scanning Radiometer (ATSR) missions. It is fast and independent from external constrains. The first version of the algorithm was applied to the whole ATSR missions and produced a 20-year day-night TCWV dataset over sea in clear sky conditions. Comparison of retrieved TCWV with values from both satellite (e.g. the Special Sensor Microwave/Imager (SSM/I)) and radiosondes show a good agreement. The algorithm makes use of a set of tabulated parameters calculated off-line using a Radiative Transfer Model (RTM) that was specifically developed to simulate ATSR radiances. In the first version of the algorithm, these parameters were fixed along the whole globe. In order to better account for atmospheric variations (e.g. due to seasonal and latitudinal atmospheric behaviour), we produce a new version of the algorithm that exploits different sets of parameters. The AIRWAVE algorithm, in both its versions, rely on the relative behaviour of measured Brightness Temperature in forward and nadir directions in TIR channels. This characteristic makes it possible to easily adopt the code for other instruments having similar dual view capability and spectral channels. The Sea and Land Surface Temperature Radiometer (SLSTR), on board the European Copernicus Sentinel 3 presents ideal conditions for the extension of the AIRWAVE algorithm to its measurements. Here we will show the performances of the new version of AIRWAVE algorithm with respect to the first version applying the new algorithm to a subset of AATSR data and present preliminary calculations for the application of the new version of AIRWAVE to SLSTR measurements.