Object of this work is to explore the capabilities of multi-sensor water vapor (WV) observations for identification and classification of fronts and air masses in northern Atlantic and Mediterranean areas. We used data from the 6.3 micromete channel of the European geostationary satellite Meteosat: we retrieved the distribution of WV mean content in the layer between 600 and 300 hPa for cloudless areas. Multifrequency data from Special Sensor Microwave/Imager (SSM/I) are used to estimate: 1) the distribution of WV mean content in lowermost 500 m of the troposphere, and 2) the distribution of total WV content in the troposphere. The retrieval is performed over marine areas and outside heavy precipitation areas. We combined the three WV retrievals and we estimated the vertical WV profile at three tropospheric levels: the lowest one below 500 m (1000-960 hPa, from the SSM/I), the layer between 600 and 300 hPa (from the Meteosat) and the layer between 500 m and 600 hPa (as difference between these two fields and the total columnar content as from SSM/I). The performances of the three techniques are evaluated by comparison with European Center for Medium Range Weather Forecast (ECMWF) analysis: good agreement is found for both SSM/I retrievals (percentage of error between 15 and 25%) while for the 6.3 micrometer retrieval higher values are reported (about 45%). The combined approach is used to estimate vertical profiles of WV content with an accuracy suitable for semi-quantitative analysis of the moisture structure. Vertical cross sections of WV fields are obtained in proximity of frontal surfaces and discussed for one case study.
Estimation of water vapor vertical distribution over the sea from Meteosat and SSM/I observations
PORCU', Federico;
2000
Abstract
Object of this work is to explore the capabilities of multi-sensor water vapor (WV) observations for identification and classification of fronts and air masses in northern Atlantic and Mediterranean areas. We used data from the 6.3 micromete channel of the European geostationary satellite Meteosat: we retrieved the distribution of WV mean content in the layer between 600 and 300 hPa for cloudless areas. Multifrequency data from Special Sensor Microwave/Imager (SSM/I) are used to estimate: 1) the distribution of WV mean content in lowermost 500 m of the troposphere, and 2) the distribution of total WV content in the troposphere. The retrieval is performed over marine areas and outside heavy precipitation areas. We combined the three WV retrievals and we estimated the vertical WV profile at three tropospheric levels: the lowest one below 500 m (1000-960 hPa, from the SSM/I), the layer between 600 and 300 hPa (from the Meteosat) and the layer between 500 m and 600 hPa (as difference between these two fields and the total columnar content as from SSM/I). The performances of the three techniques are evaluated by comparison with European Center for Medium Range Weather Forecast (ECMWF) analysis: good agreement is found for both SSM/I retrievals (percentage of error between 15 and 25%) while for the 6.3 micrometer retrieval higher values are reported (about 45%). The combined approach is used to estimate vertical profiles of WV content with an accuracy suitable for semi-quantitative analysis of the moisture structure. Vertical cross sections of WV fields are obtained in proximity of frontal surfaces and discussed for one case study.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
