A comparison between TOPEX microwave radiometer, ERS 1 microwave radiometer, and European Centre for Medium‐Range Weather Forecasting derived wet tropospheric corrections

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Abstract
A comparison study has been carried out between the two wet tropospheric corrections in the TOPEX/POSEIDON merged geophysical data records. It is shown that the TOPEX microwave radiometer (TMR) wet tropospheric correction monitors 100‐ to 1000‐km water vapor scales better than the European Centre for Medium‐Range Weather Forecasting (ECMWF) derived wet tropospheric correction. The standard deviation for both corrections is about 3 cm, with a tendency for the ECMWF model to give higher humidities than TMR in very wet atmospheres. The ECMWF correction is of fairly high quality and could be used if the TMR fails. The TOPEX and ERS 1 microwave radiometer wet tropospheric corrections are also compared in the vicinity of TOPEX/ERS 1 crossovers. The standard deviation at crossovers is about 1 cm, with no bias. Along‐track comparison shows that the two radiometers perform similarly, except in high winds or rain. The small discrepancies may be due to differences in the antenna beams or in the geophysical transfer functions.