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See detailTrends of ozone total columns and vertical distribution from FTIR observations at 8 NDACC stations around the globe
Vigouroux, C; Blumenstock, T; Coffey, M et al

in Atmospheric Chemistry & Physics Discussions (2014), 14

Ground-based Fourier transform infrared (FTIR) measurements of solar absorption spectra can provide ozone total columns with a precision of 2%, but also independent partial column amounts in about four ... [more ▼]

Ground-based Fourier transform infrared (FTIR) measurements of solar absorption spectra can provide ozone total columns with a precision of 2%, but also independent partial column amounts in about four vertical layers, one in the troposphere and three in the stratosphere up to about 45 km, with a precision of 5–6%. We use eight of the Network for the Detection of Atmospheric Compososition Change (NDACC) stations having a long-term time series of FTIR ozone measurements to study the total and vertical ozone trends and variability, namely: Ny-Alesund (79° N), Thule (77° N), Kiruna (68° N), Harestua (60° N), Jungfraujoch (47° N), Izaña (28° N), Wollongong (34° S) and Lauder (45° S). The length of the FTIR time-series varies by station, but is typically from about 1995 to present. We applied to the monthly means of the ozone total and four partial columns a stepwise multiple regression model including the following proxies: solar cycle, Quasi-Biennial Oscillation (QBO), El Niño-Southern Oscillation (ENSO), Arctic and Antarctic Oscillation (AO/AAO), tropopause pressure (TP), equivalent latitude (EL), Eliassen-Palm flux (EPF), and volume of polar stratospheric clouds (VPSC). At the Arctic stations, the trends are found mostly negative in the troposphere and lower stratosphere, very mixed in the middle stratosphere, positive in the upper stratosphere due to a large increase in the 1995–2003 period, and non-significant when considering the total columns. The trends for mid-latitude and subtropical stations are all non-significant, except at Lauder in the troposphere and upper stratosphere, and at Wollongong for the total columns and the lower and middle stratospheric columns; at Jungfraujoch, the upper stratospheric trend is close to significance (+0.9 ± 1.0 % decade−1). Therefore, some signs of the onset of ozone mid-latitude recovery are observed only in the Southern Hemisphere, while a few more years seems to be needed to observe it at the northern mid-latitude station. [less ▲]

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See detailCarbon monoxide (CO) and ethane (C2H6) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model
Angelbratt, J.; Mellqvist, J.; Simpson, D. et al

in Atmospheric Chemistry and Physics (2011), 11(17), 9253--9269

Trends in the CO and C2H6 partial columns ~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 ... [more ▼]

Trends in the CO and C2H6 partial columns ~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 C2H6 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-σ 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 CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. 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 C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 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 C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed. [less ▲]

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See detailA new method to detect long term trends of methane (CH4) and nitrous oxide (N2O) total columns measured within the NDACC ground-based high resolution solar FTIR network
Angelbratt, J.; Mellqvist, J.; Blumenstock, T. et al

in Atmospheric Chemistry and Physics (2011), 11(13), 6167--6183

Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a ... [more ▼]

Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a multiple regression model with anomalies of air pressure, total columns of hydrogen fluoride (HF) and carbon monoxide (CO) and tropopause height are used to reduce the variability in the methane (CH4) and nitrous oxide (N2O) total columns to estimate reliable linear trends with as small uncertainties as possible. The method is developed at the Harestua station (60 N, 11 E, 600m a.s.l.) and used on three other European FTIR stations, i.e. Jungfraujoch (47 N, 8 E, 3600m a.s.l.), Zugspitze (47 N, 11 E, 3000m a.s.l.), and Kiruna (68 N, 20 E, 400m a.s.l.). Linear CH4 trends between 0.13±0.01-0.25±0.02%yr-1 were estimated for all stations in the 1996-2009 period. A piecewise model with three separate linear trends, connected at change points, was used to estimate the short term fluctuations in the CH4 total columns. This model shows a growth in 1996–1999 followed by a period of steady state until 2007. From 2007 until 2009 the atmospheric CH4 amount increases between 0.57±0.22–1.15±0.17%yr-1. Linear N2O trends between 0.19±0.01–0.40±0.02%yr-1 were estimated for all stations in the 1996-2007 period, here with the strongest trend at Harestua and Kiruna and the lowest at the Alp stations. From the N2O total columns crude tropospheric and stratospheric partial columns were derived, indicating that the observed difference in the N2O trends between the FTIR sites is of stratospheric origin. This agrees well with the N2O measurements by the SMR instrument onboard the Odin satellite showing the highest trends at Harestua, 0.98±0.28%yr-1, and considerably smaller trends at lower latitudes, 0.27±0.25%yr-1. The multiple regression model was compared with two other trend methods, the ordinary linear regression and a Bootstrap algorithm. The multiple regression model estimated CH4 and N2O trends that differed up to 31% compared to the other two methods and had uncertainties that were up to 300% lower. Since the multiple regression method were carefully validated this stresses the importance to account for variability in the total columns when estimating trend from solar FTIR data. [less ▲]

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See detailValidation of five years (2003–2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations
de Laat, A. T. J.; Gloudemans, A. M. S.; Schrijver, H. et al

in Atmospheric Measurement Techniques (2010), 3(5), 1457--1471

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 ... [more ▼]

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 2σ precision of 0.2 × 1018 molecules/cm2 (~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° × 8°. 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. [less ▲]

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See detailValidation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)
Dupuy, Eric; Walker, K. A.; Kar, J. et al

in Atmospheric Chemistry and Physics (2009), 9(2), 287-343

This paper presents extensive bias determination analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and ... [more ▼]

This paper presents extensive bias determination analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45 60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about + 20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within +/- 10% (average values within +/- 6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (similar to 35-55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to -10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45-55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements. [less ▲]

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See detailEvaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations.
Vigouroux, C.; De Mazière, M.; Demoulin, Philippe ULg et al

in Atmospheric Chemistry and Physics (2008), 362(8), 6865-6886

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See detailComparisons between SCIAMACHY Scientific Products and Ground-Based FTIR Data for Total Columns of CO, CH4 and N2O
De Mazière, M.; Barret, B.; Blumenstock, T. et al

Scientific conference (2004, May)

Total column amounts of CO, CH4 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based network of Fourier-transform infrared (FTIR ... [more ▼]

Total column amounts of CO, CH4 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based network of Fourier-transform infrared (FTIR) spectrometers as well as to data obtained with an FTIR instrument during a ship cruise in January-February 2003, along the African West Coast. The SCIAMACHY data considered here have been produced by two different scientific retrieval algorithms, wfm-doas (version 4.0) and IMLM (version 5.1), and cover different time periods, making the number of reliable coincidences that satisfy the temporal and spatial collocation criteria rather limited and different for both. Also the quality of the SCIAMACHY Level 1 data, and thus of the Level 2 data for the different time periods is very different. Still the comparisons demonstrate the capability of SCIAMACHY, using one of both algorithms, to deliver geophysically valuable products for the target species under consideration, on a global scale. [less ▲]

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See detailGround-based FTIR measurements of O3- and climate-related gases in the free troposphere and lower stratosphere
De Mazière, M.; Barret, B.; Vigouroux, C. et al

in Zerefos, C. S. (Ed.) Proceedings Quadrennial Ozone Symposium (2004)

In the frame of the EC project UFTIR (Time series of Upper Free Troposphere observations from a European ground-based FTIR network), a common strategy for an optimal determination of the chemical ... [more ▼]

In the frame of the EC project UFTIR (Time series of Upper Free Troposphere observations from a European ground-based FTIR network), a common strategy for an optimal determination of the chemical composition in the free troposphere and lower stratosphere with ground-based Fourier-transform infrared (FTIR) spectrometers is being developed. The project focuses on 6 target species that are O3, CO, CH4, N2O, C2H6 and CHClF2 (HCFC-22). The strategy consists in selecting the most appropriate parameters to retrieve vertical concentration profiles from solar FTIR spectra. Among the important parameters are the spectral microwindows: they have been optimised to maximise the information content and to minimize the influence of poorly known spectroscopic data and interfering species. [less ▲]

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See detailVALIDATION OF ENVISAT-1 LEVEL-2 PRODUCTS RELATED TO LOWER ATMOSPHERE O3 AND NOy CHEMISTRY BY A FTIR QUASI-GLOBAL NETWORK
De Mazière, M.; Coosemans, T.; Barret, B. et al

Scientific conference (2002, December)

A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to ... [more ▼]

A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to contribute to the validation of the three atmospheric chemistry instruments onboard ENVISAT, that are MIPAS, SCIAMACHY and GOMOS. The target products for validation are total columns of O3, CH4, CO and some important NOy species (NO2, HNO3, NO) and the source gas N2O. Together the eleven stations cover the latitudes between 79 °N and 78°S, including polar, mid -latitude and subtropical and tropical locations. The goal is to contribute to the assessment of the data quality of the aforementioned ENVISAT instruments, from a quasi-global perspective. The period of intensive ground-based data collection for the benefit of the ENVISAT Validation Commissioning Phase that is dealt with in the present paper is July 15 to December 1, 2002. The FTIR network involved collected a data set corresponding to an equivalent of approximately 400 days of measurements; about three quarter of the data have already been submitted to the ENVISAT Calval database and are included in the present work. Unfortunately, the distribution of ENVISAT data has been slow and limited. Only a limited number of coincidences has been found for making data inter-comparisons. Therefore, the conclusions drawn in this paper are very preliminary and cover only a limited set of data products from SCIAMACHY only. Our findings up to now concerning the above mentioned target products are the following: (1) SCIAMACHY near infrared operational products (CO, CH4, N2O) have no scientific meaning yet, (2), the operational SCIAMACHY total vertical O3 column product derived in the ultraviolet window has undergone some improvements with changing versions of the processor(s) but it still underestimates the column by about 5 – 10 %, (3), the operational SCIAMACHY total vertical O3 column product derived in the visible window is unrealistically large, and (3), the operational NO2 total column product from SCIAMACHY seems to largely overestimate the real column, but very few coincidences and large dispersions of the data do inhibit any further conclusion at present. In a next phase, the same ground-based correlative data set will be exploited to further validate the ENVISAT data as soon as more and reprocessed data will be distributed. [less ▲]

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See detailGround-based FTIR Measurements from a Series of European sites during the Winter of 1995/96 and a Comparison with a 3D Chemical Transport Model: Evidence of Chlorine Activation and Ozone depletion
Paton Walsh, C.; Bell, W.; Blumenstock, T. et al

in Harris, N. R. P.; Kilbane-Dawe, I.; Amanatidis, G.T. (Eds.) Polar stratospheric ozone 1997 (1998)

Fourier transform infra-red (FTIR) measurements of stratospheric trace species have been made at a network of five ground-based sites from 79°N to 47°N during the Northern hemisphere winter of 1995/1996 ... [more ▼]

Fourier transform infra-red (FTIR) measurements of stratospheric trace species have been made at a network of five ground-based sites from 79°N to 47°N during the Northern hemisphere winter of 1995/1996. This winter was extremely cold with temperatures below the threshold for type 1 polar stratospheric cloud (PSC) formation from mid December 1995 until early March 1996 when there was a rapid warming of the stratosphere. Over 25 days experienced temperatures low enough for ice cloud (PSC type 2) formation. Vertical columns values for HCl, ClONO2, HF and HNO3 have been derived from FTIR measurements at the following sites: Ny Alesund, Spitzbergen (79°N, 12°E); Kiruna, Sweden (67°N, 21°E); Harestua, Norway (60°N, 11°E); London, England (51°N, 0°E) and the Jungfraujoch, Switzerland (48°N, 8°E), with measurements of other stratospheric trace gases, including O3 and ClO available from some of the sites. All of these sites are equipped with high resolution Bruker 120HR or 120M spectrometers, recording atmospheric spectra in the mid infrared using the Sun as a source. These measurements have been used to provide both evidence of substantial activation within large areas of the polar vortex and a subsequent O3 depletion. The measurements suggest a well mixed central vortex area surrounded by a vortex edge that may be highly variable in composition. The measurements also provide evidence of substantial mixing of activated air from the edge of the polar vortex into middle latitudes. Comparison with the SLIMCAT 3D chemical transport model highlights the underestimation of ClONO2 concentrations in the model, with subsequent implications for underestimating O3 loss. [less ▲]

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