scholarly journals First ground-based FTIR observations of HFC-23 at Rikubetsu, Japan, and Syowa Station, Antarctica

2021 ◽  
Author(s):  
Masanori Takeda ◽  
Hideaki Nakajima ◽  
Isao Murata ◽  
Tomoo Nagahama ◽  
Isamu Morino ◽  
...  
Keyword(s):  
Rotational Transition ◽  
In Situ Measurements ◽  
Atmospheric Gases ◽  
Syowa Station ◽  
Dry Air ◽  
Systematic Uncertainties ◽  
Infrared Spectrometer ◽  
Systematic Biases ◽  
Cape Grim

Abstract. We have developed a procedure for retrieving atmospheric abundances of HFC-23 (CHF3) with a ground-based Fourier transform infrared spectrometer (FTIR) and analysed the spectra observed at Rikubetsu, Japan (43.5° N, 143.8° E), and at Syowa Station, Antarctica (69.0° S, 39.6° E). The FTIR retrievals were carried out with the SFIT4 retrieval program, and the two spectral windows of 1138.5–1148.0 cm−1 and 1154.0–1160.0 cm−1 in the overlapping ν2 and ν5 vibrational-rotational transition bands of HFC-23 were used to avoid strong H2O absorption features. We considered O3, N2O, CH4, H2O, HDO, CFC-12 (CCl2F2), HCFC-22 (CHClF2), PAN (CH3C(O)OONO2), HCFC-141b (CH3CCl2F), and HCFC-142b (CH3CClF2) as interfering species. Vertical profiles of H2O, HDO, and CH4 are preliminarily retrieved with other independent spectral windows because these profiles may induce large uncertainties in the HFC-23 retrieval. Each HFC-23 retrieval has only one piece of vertical information with sensitivity to HFC-23 in the troposphere and the lower stratosphere. The retrieval errors mainly arise from the systematic uncertainties of the spectroscopic parameters used to obtain the HFC-23, H2O, HDO, and CH4 abundances. For comparison between FTIR-retrieved HFC-23 total columns and surface dry-air mole fractions provided by AGAGE (Advanced Global Atmospheric Gases Experiment), the FTIR-retrieved HFC-23 dry-air column-averaged mole fractions (XHFC-23) were calculated. The FTIR-retrieved XHFC-23 at Rikubetsu and Syowa Station have negative biases compared to AGAGE datasets. The trend derived from the FTIR-retrieved XHFC-23 data at Rikubetsu for December to February (DJF) data over the 1997–2010 period is 0.817 ± 0.087 ppt (parts per trillion) year−1, which is in good agreement with the trend derived from the annual global mean datasets of the AGAGE 12-box model for the same period (0.820 ± 0.011 ppt year−1). The trend of the FTIR-retrieved XHFC-23 data at Rikubetsu for DJF data over the 2007–2020 period is 0.894 ± 0.099 ppt year−1, which is smaller than the trend in the AGAGE in-situ measurements at Trinidad Head (41.1° N, 124.2° W) for the 2007–2019 period (0.984 ± 0.002 ppt year−1). The trend computed from the XHFC-23 datasets at Syowa Station over the 2007–2016 period is 0.823 ± 0.075 ppt year−1, which is consistent with that derived from the AGAGE in-situ measurements at Cape Grim (40.7° S, 144.7° E) for the same period (0.874 ± 0.002 ppt year−1). Although there are systematic biases on the FTIR-retrieved XHFC-23 at both sites, these results indicate that ground-based FTIR observations have the capability to monitor the trend of atmospheric HFC-23.

scholarly journals First ground-based Fourier transform infrared (FTIR) spectrometer observations of HFC-23 at Rikubetsu, Japan, and Syowa Station, Antarctica

2021 ◽  
Vol 14 (9) ◽  
pp. 5955-5976
Author(s):  
Masanori Takeda ◽  
Hideaki Nakajima ◽  
Isao Murata ◽  
Tomoo Nagahama ◽  
Isamu Morino ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
In Situ Measurements ◽  
Atmospheric Composition ◽  
Syowa Station ◽  
Spectroscopic Parameters ◽  
Dry Air ◽  
Systematic Uncertainties ◽  
Ftir Spectrometer

Abstract. We have developed a procedure for retrieving atmospheric abundances of HFC-23 (CHF3) with a ground-based Fourier transform infrared (FTIR) spectrometer and analyzed the spectra observed at Rikubetsu, Japan (43.5∘ N, 143.8∘ E), and at Syowa Station, Antarctica (69.0∘ S, 39.6∘ E). The FTIR retrievals were carried out with the SFIT4 retrieval program, and the two spectral windows of 1138.5–1148.0 cm−1 and 1154.0–1160.0 cm−1 in the overlapping ν2 and ν5 vibrational–rotational transition bands of HFC-23 were used to avoid strong H2O absorption features. We considered O3, N2O, CH4, H2O, HDO, CFC-12 (CCl2F2), HCFC-22 (CHClF2), peroxyacetyl nitrate (PAN) (CH3C(O)OONO2), HCFC-141b (CH3CCl2F), and HCFC-142b (CH3CClF2) to be interfering species. Vertical profiles of H2O, HDO, and CH4 are preliminarily retrieved with other independent spectral windows because these profiles may induce large uncertainties in the HFC-23 retrieval. Each HFC-23 retrieval has only one piece of vertical information with sensitivity to HFC-23 in the troposphere and the lower stratosphere. Retrieval errors mainly arise from the systematic uncertainties of the spectroscopic parameters used to obtain HFC-23, H2O, HDO, and CH4 abundances. For comparison between FTIR-retrieved HFC-23 total columns and surface dry-air mole fractions provided by AGAGE (Advanced Global Atmospheric Gases Experiment), FTIR-retrieved HFC-23 dry-air column-averaged mole fractions (XHFC-23) were calculated. The FTIR-retrieved XHFC-23 values at Rikubetsu and Syowa Station have negative biases of −15 % to −20 % and −25 % compared to the AGAGE datasets, respectively. These negative biases might mainly come from systematic uncertainties of HFC-23 spectroscopic parameters. The trend of the FTIR-retrieved XHFC-23 data at Rikubetsu was derived for December to February (DJF) observations, which are considered to represent the background values when an air mass reaching Rikubetsu has the least influence by transport of HFC-23 emissions from nearby countries. The DJF trend of Rikubetsu over the 1997–2009 period is 0.810 ± 0.093 ppt yr−1 (ppt: parts per trillion), which is in good agreement with the trend derived from the annual global mean datasets of the AGAGE 12-box model for the same period (0.820 ± 0.013 ppt yr−1). The DJF trend of Rikubetsu over the 2008–2019 period is 0.928 ± 0.108 ppt yr−1, which is consistent with the trend in the AGAGE in situ measurements at Trinidad Head (41.1∘ N, 124.2∘ W) for the same period (0.994 ± 0.001 ppt yr−1). The trend of the FTIR-retrieved XHFC-23 data at Syowa Station over the 2007–2016 period is 0.819 ± 0.071 ppt yr−1, which is consistent with that derived from the AGAGE in situ measurements at Cape Grim (40.7∘ S, 144.7∘ E) for the same period (0.874 ± 0.002 ppt yr−1). Although there are systematic biases in the FTIR-retrieved XHFC-23 at both sites, these results indicate that ground-based FTIR observations have the capability to monitor the long-term trend of atmospheric HFC-23. If this FTIR measurement technique were extended to other Network for the Detection of Atmospheric Composition Change (NDACC) ground-based FTIR sites around world, the measurements reported from these sites would complement the global AGAGE observations by filling spatial and temporal gaps and may lead to improved insights about changes in regional and global emissions of HFC-23 and its role in global warming.

scholarly journals Abundances, emissions, and loss processes of the long-lived and potent greenhouse gas octafluorooxolane (octafluorotetrahydrofuran, <i>c</i>-C<sub>4</sub>F<sub>8</sub>O) in the atmosphere

2018 ◽  
Author(s):  
Martin K. Vollmer ◽  
François Bernard ◽  
Blagoj Mitrevski ◽  
L. Paul Steele ◽  
Cathy M. Trudinger ◽  
...  
Keyword(s):  
Growth Rate ◽  
Greenhouse Gas ◽  
Infrared Absorption Spectrum ◽  
Ambient Air ◽  
Atmospheric Measurements ◽  
Air Samples ◽  
Dry Air ◽  
Atmospheric Loss ◽  
Cape Grim

Abstract. The first observations of octafluorooxolane (octafluorotetrahydrofuran, c-C4F8O), a persistent greenhouse gas, in the atmosphere are reported. In addition, a complimentary laboratory study of its most likely atmospheric loss processes and infrared absorption spectrum and global warming potential (GWP) are reported. First atmospheric measurements of c-C4F8O are provided from the Cape Grim Air Archive (41° S, Tasmania, Australia, 1978–present), supplemented by two firn air samples from Antarctica, in situ measurements of ambient air at Aspendale, Victoria (38° S), and a few archived air samples from the Northern Hemisphere. Atmospheric abundances in the Southern Hemisphere have reached 74 ppq (parts per quadrillion, femtomol mol-1 in dry air) by 2017. However its growth rate has decreased from a maximum in 2004 of 4.3 ppq yr-1 to

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

Evaluation of reanalysis and satellite-based sea surface winds using in situ measurements from Chinese Antarctic Expeditions

2013 ◽  
Vol 24 (3) ◽  
pp. 147
Author(s):  
Ming LI ◽  
Qinghua YANG ◽  
Jiechen ZHAO ◽  
Lin ZHANG ◽  
Chunhua LI ◽  
...  
Keyword(s):  
In Situ Measurements ◽  
Sea Surface ◽  
Surface Winds ◽  
Sea Surface Winds

The effects of surcharged manholes on the travel time and dispersion of solutes in sewer systems

1995 ◽  
Vol 31 (7) ◽  
pp. 51-59 ◽  
Author(s):  
Ian Guymer ◽  
Rob O'Brien
Keyword(s):  
Travel Time ◽  
Moment Method ◽  
In Situ Measurements ◽  
Time Change ◽  
Longitudinal Dispersion ◽  
Laboratory System ◽  
Environmental Load ◽  
Hydraulic Characteristics ◽  
Sewer Systems

Previously, the design of sewer systems has been limited to studies of their hydraulic characteristics, in particular the ability of the system to convey the maximum discharge. Greater environmental awareness has necessitated that new designs, and some existing schemes, are assessed to determine the environmental load which the scheme will deliver to any downstream component. This paper describes a laboratory programme which has been designed to elucidate the effects of manholes on the longitudinal dispersion of solutes. A laboratory system is described, which allows in situ measurements to be taken of the concentration of a fluorescent solute tracer, both up- and down-stream of a surcharged manhole junction. Results are presented from a preliminary series of studies undertaken for a single manhole geometry over a range of discharges, with varying levels of surcharge. Results are presented showing the variation of travel time, change in second moment of the distribution and of a dispersion factor with surcharge, assuming a Taylor approach and determining the dispersion factor using a ‘change in moment’ method. The effect of the stored volume within the manhole is clearly evident. The limitations and the applicability of this approach are discussed.

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