| 1. |
- Angelbratt, Jon, 1981, et al.
(författare)
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Carbon monoxide (CO) and ethane (C2H6) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:17, s. 9253-9269
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Tidskriftsartikel (refereegranskat)abstract
- Trends in the CO and C(2)H(6) partial columns (similar to 0-15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996-2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to -0.45 +/- 0.16%yr(-1), -1.00 +/- 0.24%yr(-1), -0.62 +/- 0.19%yr(-1) and -0.61 +/- 0.16%yr(-1), respectively. The corresponding trends for C(2)H(6) are -1.51 +/- 0.23%yr(-1), -2.11 +/- 0.30%yr(-1), -1.09 +/- 0.25%yr(-1) and -1.14 +/- 0.18%yr(-1). All trends are presented with their 2-sigma confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996-2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH(4) and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C(2)H(6) partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Alesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10-22% deviation for CO and 14-31% deviation for C(2)H(6). Their seasonal amplitude is captured within 6-35% and 9-124% for CO and C(2)H(6), respectively. However, 61-98% of the CO and C(2)H(6) partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1-9% and 37-50% of the measurements for CO and C(2)H(6), respectively. The global model sensitivity for assumptions made in this paper is also analyzed.
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| 2. |
- Blumenstock, T., et al.
(författare)
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Characterization and potential for reducing optical resonances in Fourier transform infrared spectrometers of the Network for the Detection of Atmospheric Composition Change (NDACC)
- 2021
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:2, s. 1239-1252
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Tidskriftsartikel (refereegranskat)abstract
- Although optical components in Fourier transform infrared (FTIR) spectrometers are preferably wedged, in practice, infrared spectra typically suffer from the effects of optical resonances ("channeling") affecting the retrieval of weakly absorbing gases. This study investigates the level of channeling of each FTIR spectrometer within the Network for the Detection of Atmospheric Composition Change (NDACC). Dedicated spectra were recorded by more than 20 NDACC FTIR spectrometers using a laboratory mid-infrared source and two detectors. In the indium antimonide (InSb) detector domain (1900-5000 cm-1), we found that the amplitude of the most pronounced channeling frequency amounts to 0.1 ‰ to 2.0 ‰ of the spectral background level, with a mean of (0:68±0:48) ‰ and a median of 0.60 ‰. In the mercury cadmium telluride (HgCdTe) detector domain (700-1300 cm-1), we find even stronger effects, with the largest amplitude ranging from 0.3 ‰ to 21 ‰ with a mean of (2:45±4:50) ‰ and a median of 1.2 ‰. For both detectors, the leading channeling frequencies are 0.9 and 0.11 or 0.23 cm-1 in most spectrometers. The observed spectral frequencies of 0.11 and 0.23 cm-1 correspond to the optical thickness of the beam splitter substrate. The 0.9 cm-1 channeling is caused by the air gap in between the beam splitter and compensator plate. Since the air gap is a significant source of channeling and the corresponding amplitude differs strongly between spectrometers, we propose new beam splitters with the wedge of the air gap increased to at least 0.8. We tested the insertion of spacers in a beam splitter's air gap to demonstrate that increasing the wedge of the air gap decreases the 0.9 cm-1 channeling amplitude significantly. A wedge of the air gap of 0.8 reduces the channeling amplitude by about 50 %, while a wedge of about 2 removes the 0.9 cm-1 channeling completely. This study shows the potential for reducing channeling in the FTIR spectrometers operated by the NDACC, thereby increasing the quality of recorded spectra across the network.
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| 3. |
- de Laat, A. T. J., et al.
(författare)
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Validation of five years (2003-2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations
- 2010
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 3:5, s. 1457-1471
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003-2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2 sigma precision of 0.2 x 10(18) molecules/cm(2) (similar to 10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8 degrees x 8 degrees. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid-to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003-2004 bias is consistent with previously reported results although its origin remains under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003-2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts.
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| 4. |
- Yurganov, L.N., et al.
(författare)
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A Quantitative Assessment of the 1998 Carbon Monoxide Emission Anomaly in the Northern Hemisphere Based on Total Column and Surface Concentration Measurements
- 2004
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 109:15, s. D15305-
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Tidskriftsartikel (refereegranskat)abstract
- Carbon monoxide abundances in the atmosphere have been measured between January 1996 and December 2001 in the high Northern Hemisphere (HNH) (30degrees-90degreesN) using two different approaches: total column amounts of CO retrieved from infrared solar spectra and CO mixing ratios measured in situ at ground-based stations. The data were averaged, and anomalies of the CO HNH burden ( deviations of the total tropospheric mass between 30degreesN and 90degreesN from the mean seasonal profile, determined as the 5 year average) were analyzed. The anomalies obtained from in situ and total column data agree well and both show two maxima, by far the largest in October 1998 and a lower one in August 1996. A noticeable decrease of the positive 1998 summer anomaly with increasing height was found. A box model was applied, and anomalies in source rates were obtained under the assumption of insignificant interannual sink variations. In August 1998 the HNH emission anomaly was estimated to be 38 Tg month(-1). The annual 1998 emission positive anomaly was 96 Tg yr(-1). Nearly all excess CO may be attributed to the emissions from boreal forest fires. According to available inventories, biomass burning emits around 52 Tg yr(-1) during the "normal'' years; therefore total biomass emissions in 1998 were as large as 148 Tg yr(-1). In August 1998, CO contribution from the biomass burning was twice as large as that from fossil fuel combustion. The results were compared to available emission inventories.
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| 5. |
- Gardiner, T., et al.
(författare)
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Trend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:22, s. 6719-6727
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models.
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| 6. |
- Vigouroux, C., et al.
(författare)
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Evaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:23, s. 6865-6886
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Tidskriftsartikel (refereegranskat)abstract
- Within the European project UFTIR (Time series of Upper Free Troposphere observations from an European ground-based FTIR network), six ground-based stations in Western Europe, from 79 degrees N to 28 degrees N, all equipped with Fourier Transform infrared (FTIR) instruments and part of the Network for the Detection of Atmospheric Composition Change (NDACC), have joined their efforts to evaluate the trends of several direct and indirect greenhouse gases over the period 1995-2004. The retrievals of CO, CH4, C2H6, N2O, CHClF2, and O-3 have been optimized. Using the optimal estimation method, some vertical information can be obtained in addition to total column amounts. A bootstrap resampling method has been implemented to determine annual partial and total column trends for the target gases. The present work focuses on the ozone results. The retrieved time series of partial and total ozone columns are validated with ground-based correlative data (Brewer, Dobson, UV-Vis, ozonesondes, and Lidar). The observed total column ozone trends are in agreement with previous studies: 1) no total column ozone trend is seen at the lowest latitude station Izana (28 degrees N); 2) slightly positive total column trends are seen at the two mid-latitude stations Zugspitze and Jungfraujoch (47 degrees N), only one of them being significant; 3) the highest latitude stations Harestua (60 degrees N), Kiruna (68 degrees N) and Ny-Alesund (79 degrees N) show significant positive total column trends. Following the vertical information contained in the ozone FTIR retrievals, we provide partial columns trends for the layers: ground-10 km, 10-18 km, 18-27 km, and 27-42 km, which helps to distinguish the contributions from dynamical and chemical changes on the total column ozone trends. We obtain no statistically significant trends in the ground-10 km layer for five out of the six ground-based stations. We find significant positive trends for the lower-most stratosphere at the two mid-latitude stations, and at Ny-Alesund. We find smaller, but significant trends for the 18 27 km layer at Kiruna, Harestua, Jungfraujoch, and Izana. The results for the upper layer are quite contrasted: we find significant positive trends at Kiruna, Harestua, and Jungfraujoch, and significant negative trends at Zugspitze and Izana. These ozone partial columns trends are discussed and compared with previous studies.
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| 7. |
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