Technical Note: New ground-based FTIR measurements at Ile de La Réunion: Observations, error analysis, and comparisons with independent data

ATMOSPHERIC CHEMISTRY AND PHYSICS (Impact Factor: 5.05). 01/2008; 8(13). DOI: 10.5194/acp-8-3483-2008
Source: OAI


Ground-based high spectral resolution Fourier-transform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two short-term FTIR measurement campaigns in 2002 and 2004, held at the (sub)tropical site Ile de La Réunion (21°S, 55°E). These campaigns represent the first FTIR observations carried out at this site. The results include total column amounts from the surface up to 100 km of ozone (O3), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ethane (C2H6), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3), as well as some vertical profile information for the first four mentioned trace gases. The data are characterised in terms of the vertical information content and associated error budget. In the 2004 time series, the seasonal increase of the CO concentration was observed by the end of October, along with a sudden rise that has been attributed to biomass burning events in southern Africa and Madagascar. This attribution was based on trajectory modeling. In the same period, other biomass burning gases such as C2H6 also show an enhancement in their total column amounts which is highly correlated with the increase of the CO total columns. The observed total column values for CO are consistent with correlative data from MOPITT (Measurements Of Pollution In The Troposphere). Comparisons between our ground-based FTIR observations and space-borne observations from ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) and HALOE (Halogen Occultation Experiment) confirm the feasibility of the FTIR measurements at Ile de La Réunion.

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Available from: Bart Dils, Oct 01, 2015
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    • "The lack of observations is mostly due to the inaccessibility of the tropical forests, as well as the lower priorities given to this region in the past. Ground-based solar absorption FTIR measurements of methane have been reported for Mauna Loa, Hawaii (19.5 • N, 155.6 • W) during February 1987 (Rinsland et al., 1988) and at Ile de La Réunion (21 • S, 55 • E) during two measurement campaigns in 2002 and 2004 (Senten et al., 2008). Both sites are located in the outer regions of the tropics . "
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    ABSTRACT: Total column concentrations of methane have been retrieved from ground-based solar absorption FTIR spectra in the near-infrared recorded in Paramaribo (Suriname). The methane FTIR observations are compared with TM5 model simulations and satellite observations from SCIAMACHY, and represent the first validation of SCIAMACHY retrievals in the inner tropics using ground-based remote sensing techniques. Apart from local biomass burning features, our methane FTIR observations agree well with TM5 model simulations. The comparison of the direct measured CH4/CO2 ratios by FTIR and satellite reveals that the satellite can hardly detect methane emissions of tropical biomass burning due to the used retrieval method.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 08/2010; 10(15). DOI:10.5194/acp-10-7231-2010 · 5.05 Impact Factor
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    • "On the other hand, Wollongong and Darwin, Australia, are located close to emission sources and show large increases in CO related to near-by forest fires (Paton-Walsh et al., 2005, 2009). For Réunion limited observations are available but nevertheless the increase in CO during the tropical biomass burning season in the southern half of Africa is present, when Réunion is located under outflow of African biomass burning plumes (Duflot et al., 2010; Senten et al., 2008). "
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    ABSTRACT: This paper presents a validation study of SCIAMACHY CO total column measurements from the 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 a previously reported Southern Hemisphere bias based on comparisons with MOPITT CO and is currently 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.
    Atmospheric Measurement Techniques 07/2010; 3(4). DOI:10.5194/amt-3-1457-2010 · 2.93 Impact Factor
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    • "For more than one decade, there has been wide interest in investigateing the contribution of anthropogenic and biomass burning sources of CO to its observed global distributions. Insight into the amount, distribution, trends and variability of the CO burden on the global 10 scale are available from surface in situ measurements, column and profile retrievals from remote ground sites and more recently from space (Rinsland and Levine, 1985; Pougatchev and Rinsland, 1995; Barret et al., 2003; Edwards et al., 2004; Yurganov et al., 2004, 2005, 2008; Sussmann and Buchwitz, 2005; Dils et al., 2006; Turquety et al., 2008; Clerbaux et al., 2008; Senten et al., 2008) and references therein. A recent 15 study (Halland et al., 2008) presented how the CO profiles retrieved from a satellite, can be used to trace and identify convective vertical transport from the boundary layer to the free troposphere. "
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    ABSTRACT: Carbon monoxide (CO) is an important pollutant in urban agglomerations. Quantifying the total burden of this pollutant in a megacity is challenging because not only its surface concentration but also its vertical dispersion present different behaviours and high variability. The diurnal trend of columnar CO in the boundary layer of Mexico City has been measured during various days with ground-based infrared absorption spectroscopy. Daytime CO total columns are retrieved from solar spectra and for the first time, nocturnal CO total columns using moonlight have been retrieved within a megacity. The measurements were taken at the Universidad Nacional Autónoma de México (UNAM) campus located in Mexico City (19.33° N, 99.18° W, 2260 m a.s.l.) from October 2007 until February 2008 with a Fourier-transform infrared spectrometer at 0.5 cm−1 resolution. The atmospheric CO background column was measured from the high altitude site Altzomoni (19.12° N, 98.65° W, 4010 m a.s.l.) located 60 km southeast of Mexico City. The total CO column within the city presents large variations. Fresh CO emissions at the surface, the transport of cleaner or more polluted air masses within the field-of-view of the instrument and other processes contribute to this variability. The mean background value above the boundary mixing layer was found to be (8.4±0.5)×1017 molecules/cm2, while inside the city, the late morning mean on weekdays and Sundays was found to be (2.73±0.41)×1018 molecules/cm2 and (2.04±0.57)×1018 molecules/cm2, respectively. Continuous CO column retrieval during the day and night (when available), in conjunction with surface CO measurements, allow for a reconstruction of the effective mixing layer height. The limitations from this simplified approach, as well as the potential of using continuous column measurements in order to derive top-down CO emissions from a large urban area, are discussed. Also, further monitoring will provide more insight in daily and weekly emission patterns and a usable database for the quantitative validation of CO from satellite observations in a megacity.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 10/2009; 9(20). DOI:10.5194/acp-9-8061-2009 · 5.05 Impact Factor
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