scholarly journals The air-broadened, near-infrared CO2 line shape in the spectrally isolated regime: Evidence of simultaneous Dicke narrowing and speed dependence

2011 ◽  
Vol 135 (6) ◽  
pp. 064308 ◽  
Author(s):  
David A. Long ◽  
Katarzyna Bielska ◽  
Daniel Lisak ◽  
Daniel K. Havey ◽  
Mitchio Okumura ◽  
...  
Keyword(s):  
Line Shape ◽  
Near Infrared ◽  
Speed Dependence

scholarly journals Using a speed-dependent Voigt line shape to retrieve O<sub>2</sub> from Total Carbon Column Observing Network solar spectra to improve measurements of XCO<sub>2</sub>

2019 ◽  
Vol 12 (1) ◽  
pp. 35-50 ◽  
Author(s):  
Joseph Mendonca ◽  
Kimberly Strong ◽  
Debra Wunch ◽  
Geoffrey C. Toon ◽  
David A. Long ◽  
...  
Keyword(s):  
Line Shape ◽  
Near Infrared ◽  
Total Carbon ◽  
Absorption Coefficients ◽  
Line Shapes ◽  
Shape Models ◽  
Speed Dependence ◽  
Measured Absorption ◽  
The Difference ◽  
Carbon Dioxide Co2

Abstract. High-resolution, laboratory, absorption spectra of the a1Δg←X3Σg- oxygen (O2) band measured using cavity ring-down spectroscopy were fitted using the Voigt and speed-dependent Voigt line shapes. We found that the speed-dependent Voigt line shape was better able to model the measured absorption coefficients than the Voigt line shape. We used these line shape models to calculate absorption coefficients to retrieve atmospheric total columns abundances of O2 from ground-based spectra from four Fourier transform spectrometers that are a part of the Total Carbon Column Observing Network (TCCON). Lower O2 total columns were retrieved with the speed-dependent Voigt line shape, and the difference between the total columns retrieved using the Voigt and speed-dependent Voigt line shapes increased as a function of solar zenith angle. Previous work has shown that carbon dioxide (CO2) total columns are better retrieved using a speed-dependent Voigt line shape with line mixing. The column-averaged dry-air mole fraction of CO2 (XCO2) was calculated using the ratio between the columns of CO2 and O2 retrieved (from the same spectra) with both line shapes from measurements taken over a 1-year period at the four sites. The inclusion of speed dependence in the O2 retrievals significantly reduces the air mass dependence of XCO2, and the bias between the TCCON measurements and calibrated integrated aircraft profile measurements was reduced from 1 % to 0.4 %. These results suggest that speed dependence should be included in the forward model when fitting near-infrared CO2 and O2 spectra to improve the accuracy of XCO2 measurements.

scholarly journals Improving the Retrieval of XCO<sub>2</sub> from Total Carbon Column Network Solar Spectra

2018 ◽  
Author(s):  
Joseph Mendonca ◽  
Kimberly Strong ◽  
Debra Wunch ◽  
Geoffrey C. Toon ◽  
David A. Long ◽  
...  
Keyword(s):  
High Resolution ◽  
Absorption Spectra ◽  
Line Shape ◽  
Near Infrared ◽  
Total Carbon ◽  
Absorption Coefficients ◽  
Line Shapes ◽  
Speed Dependence ◽  
The Difference ◽  
One Year

Abstract. High-resolution absorption spectra of the a1∆g←X3Σg− O2 band measured using cavity ring-down spectroscopy were fitted using the Voigt and speed-dependent Voigt line shapes. We found that the speed-dependent Voigt line shape was better able to model the measured absorption coefficients than the Voigt line shape. Total columns of O2 were retrieved from ground-based high-resolution absorption spectra from four Total Carbon Column Observing Network (TCCON) sites using both Voigt and speed-dependent Voigt line shapes to calculate absorption coefficients. A lower O2 concentration was retrieved with the speed-dependent Voigt line shape, with the difference increasing as a function of solar zenith angle. CO2 total columns were also retrieved from the same spectra using a Voigt line shape and speed-dependent Voigt with line mixing. The column-averaged dry-air mole fraction of CO2 (XCO2) was calculated using the CO2 and O2 columns retrieved with both line shapes from measurements made over a one-year period at the four sites and compared. The inclusion of speed dependence reduces the airmass dependence of XCO2. The TCCON empirical airmass correction factor for XCO2 derived from a year of measurements from TCCON sites at Darwin, Lamont, and Park Falls for XCO2 improved from −0.0071±0.0057 to −0.0012±0.0054 when speed dependence was included. XCO2 retrieved with the Voigt and speed-dependent Voigt line shapes was compared to aircraft profiles measured at 13 TCCON sites. The bias between the TCCON measurements and the integrated aircraft profile measurements was reduced from 0.9897±0.0005 to 1.0041±0.0005 for XCO2 retrieved with the Voigt and speed-dependent Voigt line shapes respectively. These results suggest that speed dependence should be included in the forward model when fitting near-infrared CO2 and O2 spectra to improve the accuracy of XCO2 measurements.

Dicke narrowing, speed dependence and line mixing of self-broadened CO2 absorption lines in the 30013 ← 00001 band. Measurements and line shape testing

2021 ◽  
Vol 34 (5) ◽  
pp. 334-342
Author(s):  
V.A. Kapitanov ◽  
K.Yu. Osipov ◽  
A.E. Protasevich ◽  
Yu.N. Ponomarev ◽  
Ya.Ya. Ponurovskii
Keyword(s):  
Line Shape ◽  
Absorption Lines ◽  
Speed Dependence ◽  
Line Mixing

scholarly journals Laboratory spectral calibration of the TanSat atmospheric carbon dioxide grating spectrometer

2018 ◽  
Vol 7 (3) ◽  
pp. 245-252 ◽  
Author(s):  
Zhongdong Yang ◽  
Yuquan Zhen ◽  
Zenshan Yin ◽  
Chao Lin ◽  
Yanmeng Bi ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Spectral Resolution ◽  
Line Shape ◽  
Atmospheric Carbon Dioxide ◽  
Near Infrared ◽  
Shape Function ◽  
Grating Spectrometer ◽  
Spectral Calibration ◽  
Atmospheric Carbon ◽  
Line Shape Function

Abstract. TanSat is a key satellite mission in the Chinese Earth Observation program and is designed to measure the global atmospheric column-averaged dry-air CO2 mole fraction by measuring the visible and near-infrared solar-reflected spectra. The first Chinese super-high-resolution grating spectrometer for measuring atmospheric CO2 is aboard TanSat. This spectrometer is a suite incorporating three grating spectrometers that make coincident measurements of reflected sunlight in the near-infrared CO2 band near 1.61 and 2.06 µm and in the molecular oxygen (O2) A-band at 0.76 µm. The spectral resolving power (λ∕Δλ) values are ∼19 000, ∼12 800, and ∼12 250 in the O2 A-band, and the weak and strong absorption bands of CO2, respectively. This paper describes the prelaunch spectral calibration of the atmospheric carbon dioxide grating spectrometer aboard TanSat. Several critical aspects of the spectrometer, including the spectral resolution, spectral dispersion, and the instrument line shape function of each channel, which are directly related to producing the Level 1 products are evaluated in this paper. The instrument line shape function of the spectrometer is notably symmetrical and perfectly consistent across all channels in the three bands. The symmetry is better then 99.99 %, and the consistency in the worst case is better then 99.97 %, 99.98 %, and 99.98 % in the O2 A, WCO2, and SCO2 bands, respectively. The resulting variations in the spectral calibrations and the radiometric response errors are negligible. The spectral resolution characterizations meet the mission requirements. The spectral dispersions have excellent consistency in the spatial dimension of each band, and there is good linearity in the spectral dimension of each band. The RMS errors of the fitting residuals are 0.9, 1, and 0.7 pm in the O2 A-band, the WCO2 band, and the SCO2 band, respectively. Taken together, these results suggest that the spectral characterizations of the spectrometer aboard TanSat meet the mission requirements.

On line shape measurement and simulation of rovibrational transitions of water vapour in the near infrared region

2005 ◽  
Vol 401 (1-3) ◽  
pp. 135-139 ◽  
Author(s):  
Amitava Bandyopadhyay ◽  
Ayan Ray ◽  
Biswajit Ray ◽  
Pradip N. Ghosh
Keyword(s):  
Water Vapour ◽  
Line Shape ◽  
Near Infrared ◽  
Infrared Region ◽  
Shape Measurement ◽  
On Line ◽  
Near Infrared Region

scholarly journals Laboratory Spectral Calibration of the TanSat Atmospheric Carbon Dioxide Grating Spectrometer

2018 ◽  
Author(s):  
Zhongdong Yang ◽  
Yuquan Zhen ◽  
Zenshan Yin ◽  
Chao Lin ◽  
Yanmeng Bi ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Spectral Resolution ◽  
Line Shape ◽  
Atmospheric Carbon Dioxide ◽  
Near Infrared ◽  
Shape Function ◽  
Grating Spectrometer ◽  
Spectral Calibration ◽  
Atmospheric Carbon ◽  
Line Shape Function

Abstract. TanSat is a key satellite mission in the Chinese Earth Observation program and is designed to measure the global atmospheric column-averaged dry-air CO2 mole fraction by measuring the visible and near-infrared solar-reflected spectra.The first Chinese super-high-resolution grating spectrometer for measuring atmospheric CO2 is aboard TanSat. This spectrometer is a suite incorporating three grating spectrometers that make coincident measurements of reflected sunlight in the near-infrared CO2 band 5 near 1.61 and 2.06 micrometers and in the molecular oxygen (O2) A band at 0.76 micrometers. Their spectral resolving power (λ/Δλ) are ~19000, ~12800 and ~12250 in O2 A-band, WCO2 and SCO2 band respectively. This paper describes the prelaunch spectral calibration of the Atmospheric Carbon dioxide Grating Spectrometer aboard TanSat. Several critical aspects of the spectrometer, including the spectral resolution, spectral dispersion and the instrument line shape function of each channel, that are directly related to producing the Level 1 products were evaluated in this paper. The instrument line shape function of the spectrometer is notably symmetric and perfectly consistent across all channels in three bands.The variations resulting in spectral calibrations and radiometric response errors are negligible. The spectral resolution characterizations meet the mission requirements. The spectral dispersions have excellent consistency in the spatial dimension of each band, and there is good linearity in the spectral dimension of each band. Taken together, these results suggest that the spectral characterizations of the spectrometer aboard TanSat meet the mission requirements.

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