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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 7 | Copyright
Atmos. Meas. Tech., 10, 2627-2643, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 25 Jul 2017

Research article | 25 Jul 2017

Investigating the performance of a greenhouse gas observatory in Hefei, China

Wei Wang1, Yuan Tian1,2, Cheng Liu1,3,4, Youwen Sun1, Wenqing Liu1, Pinhua Xie1, Jianguo Liu1, Jin Xu1, Isamu Morino5, Voltaire A. Velazco6, David W. T. Griffith6, Justus Notholt7, and Thorsten Warneke7 Wei Wang et al.
  • 1Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, 230031, China
  • 2University of Chinese Academy of Sciences, Beijing, 10049, China
  • 3School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China
  • 4Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
  • 5Satellite Observation Center, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan
  • 6School of Chemistry, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia
  • 7University of Bremen, Institute of Environmental Physics, P.O. Box 330440, 28334 Bremen, Germany

Abstract. A ground-based high-resolution Fourier transform spectrometer (FTS) station has been established in Hefei, China to remotely measure CO2, CO and other greenhouse gases based on near-infrared solar absorption spectra. Total column measurements of atmospheric CO2 and CO were successfully obtained from July 2014 to April 2016. The spectra collected with an InSb detector in the first year were compared with those collected by an InGaAs detector from July 2015, demonstrating that InGaAs spectra have better signal-to-noise ratios and rms of spectral fitting residuals relative to InSb spectra. Consequently, the measurement precision of the retrieved XCO2 and XCO for InGaAs spectra is superior to InSb spectra, with about 0.04 and 0.09% for XCO2, and 1.07 and 2.00% for XCO within clear-sky days respectively. Daily and monthly averages of column-averaged dry air mole fraction of CO2 show a clear seasonal cycle, while the daily and monthly averages of XCO displayed no seasonal variation. Also, we analysed the relationship of the anomalies of XCO and XCO2, found that the correlations are only observable for individual days, and the data under different prevailing wind conditions during the observations displayed weak correlation. The observations based on the high-resolution FTS were also compared with the temporally coinciding measurements taken with a low-resolution solar FTS instrument, the EM27/SUN. Ratioing the daily averaged XCO2 of EM27 and FTS gives an overall calibration factor of 0.996±0.001. We also compared ground-based observations from the Tsukuba TCCON station with our observations, the results showing that the variation in phase and seasonal amplitude of XCO2 are similar to our results, but the variation of XCO in Tsukuba is quite different from our data in Hefei. To further evaluate our retrieved data, we made use of satellite measurements. The direct comparison of our observations with the Greenhouse Gases Observing Satellite (GOSAT) data shows good agreement of daily median XCO2, with a bias of −0.52ppm and standard deviation of 1.63ppm. The correlation coefficient (R2) is 0.79 for daily median XCO2 between our FTS and GOSAT observations. Daily median Orbiting Carbon Observatory 2 (OCO-2) data produce a positive bias of 0.81ppm and standard deviation of 1.73ppm relative to our ground-based data. Our daily median XCO2 also show strong correlation with OCO-2 data, with correlation coefficient (R2) of 0.83. Although there were a limited number of data during the observations due to instrument downtime and adverse weather, the results confirm the suitability of the observatory for ground-based long-term measurements of greenhouse gases with high precision and accuracy, and fulfil the requirements of the Total Carbon Column Observing Network (TCCON).

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Short summary
A ground-based high-resolution Fourier transform spectrometer (FTS) station has been established in Hefei, China to remotely measure CO2, CO and other greenhouse gases. Our research aim is to provide information for constraining regional sources and sinks, and validate satellite data, such as GOSAT, OCO-2 and TANSAT. We investigate the potential of FTS to determine the temporal variability of atmospheric CO2 and CO, and assess the ability of our observations to validate satellite data.
A ground-based high-resolution Fourier transform spectrometer (FTS) station has been established...