Atmospheric CO2 retrieval from ground based FTIR spectrometer over Shadnagar, India
Pathakoti Mahesh, Gaddamidi Sreenivas, Pamaraju Venkata Narasimha Rao, and Vinay Kumar Dadhwal
National Remote Sensing Center (NRSC), Indian Space Research Organization (ISRO), Hyderbad-500037
Received: 23 May 2016 – Accepted for review: 09 Jun 2016 – Discussion started: 13 Jun 2016
Abstract. The column-averaged volume mixing ratio (vmr) of carbon dioxide (XCO2) has been retrieved over Shadnagar (Latitude = 17.03° N, Longitude = 78.21° E), India at Near Infrared (NIR) spectra using ground based high resolution (∆ν = 0.01 cm−1) Fourier Transform InfraRed (FTIR; model IFS125M) spectrometer. It is first of its kind in India for measuring columnar and vertical mixing ratios of atmospheric trace gases and other greenhouse gases (GHGs). In the present study, retrieval of XCO2 could be performed for a week at near Sun's nadir view (solar zenith angle-SZA, ±75.0°) using line-by-line radiative transfer algorithm (LBLRTA). Vertical profiles of CO2 have been retrieved at NIR and middle IR (MIR) spectra using a version of the Fast Atmospheric Signature Code 3 (FASCODE3) model which is for the retrieval of atmospheric trace gas profiles. Error residuals between measured and fitted atmospheric transmission lie with in ±1.0 % for CO2 (6180–6380 cm−1) and O2 (7800–7940 cm−1) respectively. During analysis period mean (standard deviation, 1σ) XCO2 was observed to be 385.24 ppm (4.22 ppm) with 1.0 % of daily variation. Minimum and maximum averaged molecular column densities of CO2 (O2) are 6.15 × 1021 (3.3 × 1024) molecules/cm2 and 8.06 × 1021 (4.72 × 1024) molecules/cm2 respectively. Obtained an average high signal to noise ratio (SNR) of 833 and 625 for NIR and MIR spectra, respectively.
Mahesh, P., Sreenivas, G., Rao, P. V. N., and Dadhwal, V. K.: Atmospheric CO2 retrieval from ground based FTIR spectrometer over Shadnagar, India, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-177, 2016.