scholarly journals Calibration of sealed HCl cells used for TCCON instrumental line shape monitoring

2013 ◽  
Vol 6 (4) ◽  
pp. 7185-7215
Author(s):  
F. Hase ◽  
B. J. Drouin ◽  
C. M. Roehl ◽  
G. C. Toon ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Greenhouse Gases ◽  
Line Shape ◽  
Calibration Procedure ◽  
Total Carbon ◽  
Dry Air ◽  
Reference Cell ◽  
Instrumental Line ◽  
Shape Monitoring

Abstract. The TCCON (Total Carbon Column Observing Network) FTIR network provides highly accurate observations of greenhouse gases column-averaged dry-air mole fractions. As an important component of TCCON quality assurance measures, sealed cells filled with approx. 5 mbar of HCl are used for instrumental line shape (ILS) monitoring at all TCCON sites. Here, we introduce a calibration procedure for the HCl cells which applies a refillable, pressure-monitored reference cell filled with C2H2. Using this method, we identify residual variations of HCl purity between the TCCON cells as a non-negligible disturbance.

scholarly journals Calibration of sealed HCl cells used for TCCON instrumental line shape monitoring

2013 ◽  
Vol 6 (12) ◽  
pp. 3527-3537 ◽  
Author(s):  
F. Hase ◽  
B. J. Drouin ◽  
C. M. Roehl ◽  
G. C. Toon ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Line Shape ◽  
Individual Cell ◽  
Calibration Procedure ◽  
Total Carbon ◽  
Effective Pressure ◽  
Error Source ◽  
Secondary Importance ◽  
Instrumental Line ◽  
Network Consistency ◽  
Shape Monitoring

Abstract. The TCCON (Total Carbon Column Observing Network) FTIR (Fourier transform infrared) network provides highly accurate observations of greenhouse gas column-averaged dry-air mole fractions. As an important component of TCCON quality assurance, sealed cells filled with approximately 5 mbar of HCl are used for instrumental line shape (ILS) monitoring at all TCCON sites. Here, we introduce a calibration procedure for the HCl cells which employs a refillable, pressure-monitored reference cell filled with C2H2. Using this method, we identify variations of HCl purity between the TCCON cells as a non-negligible disturbance. The new calibration procedure introduced here assigns effective pressure values to each individual cell to account for additional broadening of the HCl lines. This approach will improve the consistency of the network by significantly reducing possible station-to-station biases due to inconsistent ILS results from different HCl cells. We demonstrate that the proposed method is accurate enough to turn the ILS uncertainty into an error source of secondary importance from the viewpoint of network consistency.

scholarly journals Calibration and instrumental line shape characterization of a set of portable FTIR spectrometers for detecting greenhouse gas emissions

2015 ◽  
Vol 8 (7) ◽  
pp. 3047-3057 ◽  
Author(s):  
M. Frey ◽  
F. Hase ◽  
T. Blumenstock ◽  
J. Groß ◽  
M. Kiel ◽  
...  
Keyword(s):  
Line Shape ◽  
External Source ◽  
Calibration Procedure ◽  
Total Carbon ◽  
Instrumental Performance ◽  
Solar Absorption ◽  
Ground Pressure ◽  
Before And After ◽  
Instrumental Line ◽  
The Individual

Abstract. A comprehensive calibration procedure for mobile, low-resolution, solar-absorption FTIR spectrometers, used for greenhouse gases observations, is developed. These instruments commend themselves for campaign use and deployment at remote sites. The instrumental line shape (ILS) of each spectrometer has been thoroughly characterized by analyzing the shape of H2O signatures in open path spectra. A setup for the external source is suggested and the invariance of derived ILS parameters with regard to chosen path length is demonstrated. The instrumental line shape characteristics of all spectrometers were found to be close to nominal. Side-by-side solar observations before and after a campaign, which involved shipping of all spectrometers to a selected target site and back, are applied for verifying the temporal invariability of instrumental characteristics and for deriving intercalibration factors for XCO2 and XCH4, which take into account residual differences of instrumental characteristics. An excellent level of agreement and stability was found between the different spectrometers: the uncorrected biases in XCO2 and XCH4 are smaller than 0.01 and 0.15 %, respectively, and the drifts are smaller than 0.005 and 0.035 %. As an additional sensitive demonstration of the instrumental performance we show the excellent agreement of ground pressure values obtained from the total column measurements of O2 and barometric records. We find a calibration factor of 0.9700 for the spectroscopic measurements in comparison to the barometric records and a very small scatter between the individual spectrometers (0.02 %). As a final calibration step, using a co-located TCCON (Total Carbon Column Observation Network) spectrometer as a reference, a common scaling factor has been derived for the XCO2 and XCH4 products, which ensures that the records are traceable to the WMO in situ scale.

scholarly journals Technical note: Sensitivity of instrumental line shape monitoring for the ground-based high-resolution FTIR spectrometer with respect to different optical attenuators

2017 ◽  
Vol 10 (3) ◽  
pp. 989-997 ◽  
Author(s):  
Youwen Sun ◽  
Mathias Palm ◽  
Christine Weinzierl ◽  
Christof Petri ◽  
Justus Notholt ◽  
...  
Keyword(s):  
High Resolution ◽  
Line Shape ◽  
Radiant Energy ◽  
Technical Note ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
Incident Intensity ◽  
Instrumental Line ◽  
Ftir Spectrometer ◽  
Potential Strategy

Abstract. The TCCON (Total Carbon Column Observing Network) and most NDACC (Network for Detection of Atmospheric Composition Change) sites assume an ideal ILS (instrumental line shape) for analysis of the spectra. In order to adapt the radiant energy received by the detector, an attenuator or different sizes of field stop can be inserted in the light path. These processes may alter the alignment of a high-resolution FTIR (Fourier transform infrared) spectrometer, and may result in bias due to ILS drift. In this paper, we first investigated the sensitivity of the ILS monitoring with respect to application of different kinds of attenuators for ground-based high-resolution FTIR spectrometers within the TCCON and NDACC networks. Both lamp and sun cell measurements were conducted after the insertion of five different attenuators in front of and behind the interferometer. The ILS characteristics derived from lamp and sun spectra are in good agreement. ILSs deduced from all lamp cell measurements were compared. As a result, the disturbances to the ILS of a high-resolution FTIR spectrometer with respect to the insertion of different attenuators at different positions were quantified. A potential strategy to adapt the incident intensity of a detector was finally deduced.

scholarly journals Satellite and Ground-based Measurements of X<sub>CO<sub>2</sub></sub> in a Remote Semi-Arid Region of Australia

2019 ◽  
Author(s):  
Voltaire A. Velazco ◽  
Nicholas M. Deutscher ◽  
Isamu Morino ◽  
Osamu Uchino ◽  
Beata Bukosa ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Calibration Curve ◽  
Arid Region ◽  
Total Carbon ◽  
Random Errors ◽  
Clam Shell ◽  
Dry Air ◽  
Semi Arid Region ◽  
The University ◽  
Semi Arid

Abstract. In this study, we present ground-based measurements of column-averaged dry-air mole fractions (DMFs) of CO2 (or XCO2) from an EM27/SUN portable spectrometer, equipped with an automated clam shell cover, taken in a semi-arid region of Australia. We compared these measurements to space-based XCO2 retrievals from the Greenhouse Gases Observing Satellite (GOSAT). Side-by-side measurements of EM27/SUN with the Total Carbon Column Observing Network (TCCON) instrument at the University of Wollongong were conducted in 2015–2016 to derive an XCO2 calibration factor of 0.9954 relative to TCCON. Although we found a slight drift of .0125 % per month in the calibration curve of the EM27/SUN vs TCCON XCO2, the alignment of the EM27/SUN proved stable enough for a campaign, keeping the retrieved Xair values, a measure of stability, to within 0.5 % and the modulation efficiency to within 2 %. From the measurements in Alice Springs, we confirm a small bias of around 2 ppm in the GOSAT M-gain to H-gain XCO2 retrievals, as reported by the NIES GOSAT validation team. Based on the reported random errors from GOSAT, we estimate the required duration of a future campaign in order to improve the estimated bias between the EM27/SUN and GOSAT. The dataset from the Alice Springs measurements is accessible at http://dx.doi.org/10.4225/48/5b21f16ce69bc (Velazco et al., 2018).

scholarly journals Satellite and ground-based measurements of XCO<sub>2</sub> in a remote semiarid region of Australia

2019 ◽  
Vol 11 (3) ◽  
pp. 935-946 ◽  
Author(s):  
Voltaire A. Velazco ◽  
Nicholas M. Deutscher ◽  
Isamu Morino ◽  
Osamu Uchino ◽  
Beata Bukosa ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Calibration Curve ◽  
Scaling Factor ◽  
Total Carbon ◽  
Semiarid Region ◽  
Random Errors ◽  
Dry Air ◽  
The University

Abstract. In this study, we present ground-based measurements of column-averaged dry-air mole fractions (DMFs) of CO2 (or XCO2) taken in a semiarid region of Australia with an EM27/SUN portable spectrometer equipped with an automated clamshell cover. We compared these measurements to space-based XCO2 retrievals from the Greenhouse Gases Observing Satellite (GOSAT). Side-by-side measurements of EM27/SUN with the Total Carbon Column Observing Network (TCCON) instrument at the University of Wollongong were conducted in 2015–2016 to derive an XCO2 scaling factor of 0.9954 relative to TCCON. Although we found a slight drift of 0.13 % over 3 months in the calibration curve of the EM27/SUN vs. TCCON XCO2, the alignment of the EM27/SUN proved stable enough for a 2-week campaign, keeping the retrieved Xair values, another measure of stability, to within 0.5 % and the modulation efficiency to within 2 %. From the measurements in Alice Springs, we confirm a small bias of around 2 ppm in the GOSAT M-gain to H-gain XCO2 retrievals, as reported by the NIES GOSAT validation team. Based on the reported random errors from GOSAT, we estimate the required duration of a future campaign in order to better understand the estimated bias between the EM27/SUN and GOSAT. The dataset from the Alice Springs measurements is accessible at https://doi.org/10.4225/48/5b21f16ce69bc (Velazco et al., 2018).

scholarly journals A method for evaluating bias in global measurements of CO<sub>2</sub> total columns from space

2011 ◽  
Vol 11 (7) ◽  
pp. 20899-20946 ◽  
Author(s):  
D. Wunch ◽  
P. O. Wennberg ◽  
G. C. Toon ◽  
B. J. Connor ◽  
B. Fisher ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Ground Truth ◽  
Systematic Errors ◽  
Total Carbon ◽  
Tropospheric Temperature ◽  
Dry Air ◽  
Larger Sample ◽  
Total Column

Abstract. We describe a method of evaluating systematic errors in measurements of total column dry-air mole fractions of CO2 (XCO2) from space, and we illustrate the method by applying the method to the Atmospheric CO2 Observations from Space retrievals of the Greenhouse Gases Observing Satellite (ACOS-GOSAT) v2.8 data. The approach exploits the lack of large gradients in XCO2 south of 25° S to identify large-scale offsets and other biases in the ACOS-GOSAT data with several retrieval parameters and errors in instrument calibration. We demonstrate the effectiveness of the method by comparing the ACOS-GOSAT data in the Northern Hemisphere with ground truth provided by the Total Carbon Column Observing Network (TCCON). We use the correlation between free-tropospheric temperature and XCO2 in the Northern Hemisphere to define a dynamically informed coincidence criterion between the ground-based TCCON measurements and the ACOS-GOSAT measurements. We illustrate that this approach provides larger sample sizes, hence giving a more robust comparison than one that simply uses time, latitude and longitude criteria. Our results show that the agreement with the TCCON data improves after accounting for the systematic errors.

scholarly journals Intercomparison of Total Carbon Column Observing Network (TCCON) data from two Fourier transform spectrometers at Lauder, New Zealand

2021 ◽  
Vol 14 (2) ◽  
pp. 1501-1510
Author(s):  
David F. Pollard ◽  
John Robinson ◽  
Hisako Shiona ◽  
Dan Smale
Keyword(s):  
Fourier Transform ◽  
New Zealand ◽  
Greenhouse Gases ◽  
Total Carbon ◽  
Average Difference ◽  
Dry Air ◽  
Routine Measurement ◽  
Observation Systems ◽  
Systematic Methodology ◽  
Observing Systems

Abstract. We describe the change in operational instrument for the routine measurement of column-averaged dry-air mole fraction of several greenhouse gases (denoted Xgas) at the Lauder Total Carbon Column Observing Network (TCCON) site and the steps taken to demonstrate comparability between the two observation systems following a systematic methodology. Further, we intercompare retrieved Xgas values during an intensive intercomparison period during October and November 2018, when both instruments were performing optimally, and on subsequent, less frequent occasions. The average difference between the two observing systems was found to be well below the expected level of uncertainty for TCCON retrievals for all compared species. In the case of XCO2 the average difference was 0.0264±0.0465 % (0.11±0.19 µmol mol−1).

scholarly journals Improvement of the retrieval algorithm for GOSAT SWIR XCO<sub>2</sub> and XCH<sub>4</sub> and their validation using TCCON data

2013 ◽  
Vol 6 (6) ◽  
pp. 1533-1547 ◽  
Author(s):  
Y. Yoshida ◽  
N. Kikuchi ◽  
I. Morino ◽  
O. Uchino ◽  
S. Oshchepkov ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gases ◽  
Solar Irradiance ◽  
Short Wavelength ◽  
Environmental Studies ◽  
Total Carbon ◽  
Retrieval Algorithm ◽  
Dry Air ◽  
Aerosol Scattering ◽  
Standard Deviations

Abstract. The column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) have been retrieved from Greenhouse gases Observing SATellite (GOSAT) Short-Wavelength InfraRed (SWIR) observations and released as a SWIR L2 product from the National Institute for Environmental Studies (NIES). XCO2 and XCH4 retrieved using the version 01.xx retrieval algorithm showed large negative biases and standard deviations (−8.85 and 4.75 ppm for XCO2 and −20.4 and 18.9 ppb for XCH4, respectively) compared with data of the Total Carbon Column Observing Network (TCCON). Multiple reasons for these error characteristics (e.g., solar irradiance database, handling of aerosol scattering) are identified and corrected in a revised version of the retrieval algorithm (version 02.xx). The improved retrieval algorithm shows much smaller biases and standard deviations (−1.48 and 2.09 ppm for XCO2 and −5.9 and 12.6 ppb for XCH4, respectively) than the version 01.xx. Also, the number of post-screened measurements is increased, especially at northern mid- and high-latitudinal areas.

scholarly journals Intercomparison of TCCON data from two Fourier transform spectrometers at Lauder, New Zealand

2020 ◽  
Author(s):  
David F. Pollard ◽  
John Robinson ◽  
Hisako Shiona ◽  
Dan Smale
Keyword(s):  
Fourier Transform ◽  
New Zealand ◽  
Greenhouse Gases ◽  
Total Carbon ◽  
Average Difference ◽  
Dry Air ◽  
Routine Measurement ◽  
Observation Systems ◽  
Systematic Methodology ◽  
Observing Systems

Abstract. We describe the change of operational instrument for the routine measurement of column-averaged dry-air mole fraction of several greenhouse gases (denoted Xgas) at the Lauder Total Carbon Column Observing Network (TCCON) site and the steps taken to demonstrate comparability between the two observation systems following a systematic methodology. Further, we intercompare retrieved Xgas values during an intensive intercomparison period during October and November 2018, when both instruments were performing optimally, and on subsequent, less frequent occasions. The average difference between the two observing systems was found to be well below the expected level of uncertainty for TCCON retrievals for all compared species. In the case of XCO2 the average difference was 0.0264 ± 0.0465 % (0.11 ± 0.19 μmol mol−1).

scholarly journals Improvement of the retrieval algorithm for GOSAT SWIR XCO<sub>2</sub> and XCH<sub>4</sub> and their validation using TCCON data

2013 ◽  
Vol 6 (1) ◽  
pp. 949-988 ◽  
Author(s):  
Y. Yoshida ◽  
N. Kikuchi ◽  
I. Morino ◽  
O. Uchino ◽  
S. Oshchepkov ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gases ◽  
Solar Irradiance ◽  
Short Wavelength ◽  
Total Carbon ◽  
Retrieval Algorithm ◽  
Dry Air ◽  
Error Characteristics ◽  
Aerosol Scattering ◽  
Standard Deviations

Abstract. The column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) have been retrieved from Greenhouse gases Observing SATellite (GOSAT) Short-Wavelength InfraRed (SWIR) observations. XCO2 and XCH4 retrieved using the version 01.xx retrieval algorithm showed large negative biases and standard deviations (−8.85 ppm and 4.75 ppm for XCO2 and −20.4 ppb and 18.9 ppb for XCH4, respectively) compared with data of the Total Carbon Column Observing Network (TCCON). Multiple reasons for these error characteristics (e.g. solar irradiance database, handling of aerosol scattering) are identified and corrected in a revised version of the retrieval algorithm (version 02.xx). The improved retrieval algorithm shows much smaller biases and standard deviations (−1.48 ppm and 2.10 ppm for XCO2 and −6.0 ppb and 12.5 ppb for XCH4, respectively) than the version 01.xx. Also, the number of post-screened measurements is increased especially at northern mid- and high-latitudinal area.

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