Retrieval of Total Column Carbon Dioxide over Russia from Meteor-M No. 2 Satellite Data

description is given of the method for the retrieval of atmospheric column-averaged dry-air mole fractions of carbon dioxide (XCO2) from the data of IKFS-2 infrared Fourier spectrometer on board the Meteor-M Russian meteorological satellites. The method is based on estimating XCO2 using a second-order regression, whose predictors are the effective spectral optical depths of the atmosphere in the infrared region of 8–14 μ m. The optical depth is determined using spectral intensities of outgoing radiation measured by the IKFS-2 as well as the calculated intensities of the Earth’s surface or cloud top simulated as a gray body with temperature T_s . The temperature T_s is retrieved from IKFS-2 measurements within the atmospheric microwindow at the wave number equal to 900.1 cm ^-1 . The reference XCO 2 values for constructing the regression were the results of contact CO 2 measurements on the tall tower at the ZOTTO international observatory (Central Siberia) and at the NOAA observatory on the Mauna Loa volcano (Hawaii) in 2015–2016. The methodology was validated by comparing the XCO2 retrieved from Meteor-M No. 2 IKFS-2 measurements with parallel measurements over Siberia by the OCO and CrIS satellite spectrometers on board the OCO-2 and NOAA-20 satellites (USA). The maximum discrepancies in the daily estimates of the spatially averaged XCO2 during October 9–19, 2021 derived from the IKFS-2 data do not exceed 2.3 ppm versus the OCO data and 5 ppm versus the CrIS data.