01 Feb 2019
01 Feb 2019
Status: this preprint was under review for the journal AMT but the revision was not accepted.

Retrieval of CO2, CH4, CO and N2O using ground- based FTIR data and validation against satellite observations over the Shadnagar, India

Mahesh Pathakoti1,3, Sreenivas Gaddamidi1,2, Biswadip Gharai1, Sesha Sai Mullapudi Venkata Rama1, Rajan Kumar Sundaran3, and Wei Wang4 Mahesh Pathakoti et al.
  • 1Atmospheric Chemistry and Processes Studies Division (AC&PSD), Earth and Climate Science Area (ECSA), National Remote Sensing Centre (NRSC) , Indian Space Research Organization (ISRO), Hyderabad-500037, India
  • 2Department of Physics, Jawaharlal Nehru Technological University Hyderabad-500085, India
  • 3Lab for Spatial Informatics, International Institute of Information Technology (IIIT), Hyderabad-500032, India
  • 4Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, 230031, China

Abstract. An improved column averaged concentration (X) of greenhouse gases (GHGs) namely CO2, CH4, CO and N2O are retrieved using ground-based Fourier Transform Infrared (FTIR; model IFS125M) Spectrometer data collected at Atmospheric Science Lab (ASL) of National Remote Sensing Centre (NRSC), Shadnagar, India during 2016 period in clear sky days. Indium Antimonide (InSb) detector and Calcium Fluoride (CaF2) beam splitter in combination with the spectral range between 1800 cm−1 to 11000 cm−1 (5.50 μm to 0.90 μm) with 0.01 cm−1 spectral resolution (∆ν) are set for the present study. Atmospheric transmittance for each gas was computed using PcModWin6 (MODTRAN v6) and compared against measured spectrum. In this study, spectra are analyzed using non-linear least squares spectral fitting algorithm (GFIT) developed by the California Institute of Technology, U. S. A. The Total Carbon Column Observing Network (TCCON) identified standard spectral windows were selected for retrieving the GHGs over the study site. With the present retrieval scheme, precision of the FTIR achieved are 0.17 % to 0.52 % for CO2, 0.30 % to 0.77 % for CH4, 6.33 % to 8.92 % for CO and 0.41 % to 0.75 % for N2O, respectively. Observed little to clear diurnal and seasonal variations in XCO2, XCH4, XCO and XN2O respectively. In this work, we compared FTIR retrieved GHGs against Orbiting Carbon Observatory-2 (OCO-2) retrieved XCO2 and Measurements of Pollution in the Troposphere (MOPITT) retrieved XCO. With the present retrievals, comparative study yields a mean relative bias between ground-based FTIR retrieved XCO2 and XCO are −1.50 % and 0.60 % against OCO-2 (XCO2) and MOPITT (XCO) respectively. Pearson correlation coefficient (r) between FTIR retrieval and satellite retrievals are 0.80 (XCO2, N=14 co-located) and 0.85 (XCO, N=18), respectively.

Mahesh Pathakoti et al.

Status: closed
Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Mahesh Pathakoti et al.

Mahesh Pathakoti et al.


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Latest update: 07 Dec 2022
Short summary
Present study retrieved improved dry column averaged concentrations of CO2, CH4, CO and N2O using Solar Spectra over the Shadnagar region of India using GFIT model. It is the only site which is equipped with FTIR 125M for measuring the solar spectra to retrieve the precise column GHG while meeting the TCCON standards. Present study also attempted preliminary validation of satellite retrieved column averaged concentrations of CO2 and CO against ground-based FTIR retrieved concentrations.