• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.150-157
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• 2006

Spatially resolved remote identification and quantification of trace gases in the atmosphere is desirable in various fields of scientific research as well as in public security and industrial contexts. Environmental observations investigating causes, extent md consequences of air pollution are of fundamental interest. We present an Imaging-DOAS system, a ground based remote sensing instrument that allows spatially resolved mapping of atmospheric trace gases by a differential optical absorption spectroscopy(DOAS) with sun scattered light as the light source. A passive DOAS technique permits the identification and quantification of various gases, e.g., $NO_2,\;SO_2,\;and\;CH_2O$, from their differential absorption structures with high sensitivity. The Imaging-DOAS system consists of a scanning mirror, a focusing lens, a spectrometer, a 2-D CCD, ad the integral control software. An imaging spectrometer simultaneously acquires spectral information on the incident light in one spatial dimension(column) and sequentially scans the next spatial dimension with a motorized scanning mirror. The structure of the signal acquisition system is described in detail and the evaluation method is also briefly discussed. Applications of imaging of the $NO_2$ contents in the exhaust plumes from a power plant are presented.

• Korean Journal of Remote Sensing
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• v.35 no.2
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• pp.289-298
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• 2019

In this present study, the effects of Signal to Noise Ratio (SNR), Full Width Half Maximum (FWHM), Aerosol Optical Depth (AOD), $O_3$ Vertical Column Density ($O_3$ VCD), and Solar Zenith Angle (SZA) on the accuracy of sulfur dioxide Vertical Column Density ($SO_2$ VCD) retrieval have been quantified using the Differential Optical Absorption Spectroscopy (DOAS) method with the ground-based direct-sun synthetic radiances. The synthetic radiances produced based on the Beer-Lambert-Bouguer law without consideration of the diffuse effect. In the SNR condition of 650 (1300) with FWHM = 0.6 nm, AOD = 0.2, $O_3$ VCD = 300 DU, and $SZA=30^{\circ}$, the Absolute Percentage Difference (APD) between the true $SO_2$ VCD values and those retrieved ranges from 80% (28%) to 16% (5%) for the $SO_2$ VCD of $8.1{\times}10^{15}$ and $2.7{\times}10^{16}molecules\;cm^{-2}$, respectively. For an FWHM of 0.2 nm (1.0 nm) with the $SO_2$ VCD values equal to or greater than $2.7{\times}10^{16}molecules\;cm^{-2}$, the APD ranges from 6.4% (29%) to 6.2% (10%). Additionally, when FWHM, SZA, AOD, and $O_3$ VCD values increase, APDs tend to be large. On the other hand, SNR values increase, APDs are found to decrease. Eventually, it is revealed that the effects of FWHM and SZA on $SO_2$ VCD retrieval accuracy are larger than those of $O_3$ VCD and AOD. The SZA effects on the reduction of $SO_2$ VCD retrieval accuracy is found to be dominant over the that of FWHM for the condition of $SO_2$ VCD larger than $2.7{\times}10^{16}molecules\;cm^{-2}$.