Mr. Sreenivas Gaddamidi Profile

Sreenivas Gaddamidi

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SPIE Journal Paper | 10 October 2018

Estimation of molecular column density of methane (XCH4) using AVIRIS-NG data

Mahesh Pathakoti, Biswadip Gharai, Sreenivas Gaddamidi, Rao Venkata Narshimha, Mallikarjun Kapanaboina, SeshaSai V. Mullapudi, Krishna Murthy V. Yelisetty

JARS, Vol. 12, Issue 04, 046005, (October 2018) https://doi.org/10.1117/12.10.1117/1.JRS.12.046005

KEYWORDS: FT-IR spectroscopy, Transmittance, Spectroscopy, Methane, Sensors, Carbon monoxide, Reflectivity, Spectral resolution, MODIS, Atmospheric sensing

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An attempt has been made to retrieve columnar density of methane (XCH4) over a suburban area of the Shadnagar in India from the high spatial and moderate spectral resolution (5 nm ± 0.5 nm) airborne visible/infrared imaging spectrometer next generation (AVIRIS-NG) data. The data collected were part of the joint airborne campaign by National Aeronautics Space Administration/Jet Propulsion Laboratory and Indian Space Research Organisation over several Indian sites during December 2015 to January 2016. The XCH4 was retrieved following the Moderate Resolution Imaging Spectroradiometer (MODIS) water vapor retrieval algorithm and was compared with the ground-based Fourier transform infrared (FTIR) observations. FTIR measured CH4 transmittance was fitted against Fast Atmospheric Signature Code3 (FASCODE3) simulated transmittance, and found their residual lies within ±1 % , which shows a very good retrieval sensitivity of FTIR. Hence FTIR observations are used for the validation of AVIRIS-NG derived XCH4 and found in good agreement. In the present study, we utilized airborne imaging radiance data in the CH4 absorbing channel at 2.365 ± 0.006 μm and nonabsorbing channels at 2.325 ± 0.006 μm and 2.365 ± 0.006 μm to compute atmospheric transmittance spectrum. Using a line-by-line radiative transfer algorithm, the XCH4 was estimated from AVIRIS-NG transmittance data. Prior to the application of the MODIS water vapor algorithm on AVIRIS-NG transmittance, it was also compared with the FASCODE3 simulated transmittance and found comparable. Study revealed that within the Shadnagar region, retrieved XCH4 varies little to moderate with an average of 9 × 1027 molecules cm − 2 with the highest value of 12 × 1027 molecules cm − 2 near the source region of the agriculture field. The study demonstrates the capability of AVIRIS-NG to quantify the column density of atmospheric species such as CH4 over a region.

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