MTG-IRS CORRELATION INTERFEROMETRY FOR THE RETRIEVALOF CO2 COLUMNAR AMOUNT: AN ERROR ANALYSIS STUDY

The Meteosat Third Generation geostationary satellite will be equipped with an infrared sounder sensing the Earth infrared emission in two bands between 670-1210 and 1600-2250 cm-1 with a sampling rate of 0.625 cm-1. The main objective of the infrared sounder is to retrieve temperature and water vapour profiles but its spectral coverage and resolution enable us to resolve strong and moderate hot bands of CO2. In this study we apply concepts of correlation interferometry to assess the capability of this instrument to retrieve CO2 column amount. Correlation interferometry is particularly suited for Fourier Transform Spectrometers, which observe the interferogram. By properly exploiting interferometric radiances we can isolate channels which are mostly sensitive to CO2 alone. These channels can be used to build up a linear regression between CO2 mixing ratio integrated over the atmospheric column and the radiances themselves. The methodology is capable to retrieve CO2 with an accuracy of ± 5-6 ppmv over a single unstantaneous Field of View. Once averaged over a 3x3 pixels mask the accuracy may improve to ± 1.5-2 ppmv.