Selection of Greenhouse gases Monitoring Instrument channels for CO2 in near infrared band

The Greenhouse gases Monitoring Instrument (GMI) is a high resolution infrared sounder which is specifically designed to monitor greenhouse gases concentrations. It measures CO2 column abundance in three near infrared spectral regions (the O2-A band at 0.76 μm and the CO2 band at 1.57 and 2.05 μm). The instrument presents hundreds of detector channels. In order to fast and accurate retrievals for CO2, we have developed a technique based on information content analysis to reduce the number of channels used in CO2 retrieval. The first 80 selected channels provide as much as 91.3% of the total CO2 information content. The CO2 retrievals using the selected channels compared to retrievals using all channels. The first 80 selected channels with high information content are enough to retrieve CO2 concentration and can save a lot of time. It means that the channel selection technique is reasonable and credible. This study provides theoretical guidance for the instrument design and support for fast and accurate retrieving CO2 concentration.