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Technique development for estimation of carbon dioxide concentration using radiative transfer modeling at 1.6 and 2.0 µm spectral window

Prabhunath Prasad(1), Shantanu Rastogi(1), R. P. Singh(2) and S. Panigrahy(2)

(1) DDU Gorakhpur University, Physics Department, DDU Gorakhpur University, 273009, Gorakhpur, India
(2) Space Application Centre, Remote Sensing Applications Area, Space Applica, 380015, Ahmedabad, India

Abstract

Atmospheric trace gases play crucial role in climate forcing and Green House Effect. Accurate spatially and temporally continuous estimation of the trace gases is essential for many environmental studies. Satellite observations provide important input in global monitoring of green house gases. Spectral techniques are used to derive GHG concentration by developing the relation between satellite derived differential absorption indices with gaseous concentration. The present study was aimed to simulate the effect of different CO2 concentration at different atmospheric conditions on Top Of Atmosphere (TOA) radiances in near infrared spectral region (1.6 micron & 2.0 micron). Simulation was carried out by varying CO2 concentration from 200 ppm to 800 ppm in Line-by-line (LBL) radiative transfer model (PCLnWin 3.1). Inversion equation was developed for retrieval of CO2 concentration using CIBR (Continuous Interpolated Band Ratio) technique.

Simulation experiments show the order of magnitude of radiances ranging from 5.0 x10 –15 W/cm2-str- cm-1 to 30 x10 –15 W/cm2-str- cm-1 in absorption (6210 cm-1) and transparent (6190 cm-1) bands respectively. It was found that estimated CIBR decreased (0.6 to 0.15) with increase in atmospheric CO2, concentration (200ppm – 800 ppm). It was observed that CIBR and CO2 concentration relation was dependent on the type of the atmosphere (Tropical, US, MidLW etc.). Finding of the study will be useful in retrieval of carbon dioxide concentration using satellite based sensor (SCIAMACHY, GOSAT etc) operating in Near Infrared Spectral region.