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The article focuses on a study on water vapour spectroscopy and its impact on the ratio of heavy water (HDO) and water (H2O) in Scanning Imaging Absorption spectrometer for Atmospheric Cartography (SCIAMACHY). In the study,the impact of updated water spectroscopy is tested on total column retrievals of high-resolution Fourier-Transform Spectrometers (FTS). It shows negative shift in the HDO/H2O ratio for both the SCHIAMACHY and FTS measurements.

Formaldehyde (HCHO) columns have been retrieved from ground-based Fourier transform infrared (FTIR) campaign measurements in 2004 and 2007 and from UV-Visible MAX-DOAS measurements in 2004-2005 at the NDACC site of Réunion Island (21° S, 55° E). The FTIR and MAX-DOAS daily mean formaldehyde total columns are intercompared in their common measurement period, from August to October 2004. The ground-based data are also compared to correlative SCIAMACHY data. The comparisons account for the vertical sensitivity differences of the data sets, by including their respective averaging kernels. Complete error budgets are also presented. The FTIR and MAX-DOAS daily mean total columns agree very well: no significant bias is observed and the standard deviation of the comparisons is only 8%. Both FTIR and MAX-DOAS HCHO total columns are in good agreement with SCIAMACHY values in the 2004-2005 period, with standard deviations of 21% and 31%, respectively. The same seasonal cycle is observed by the different instruments, with a minimum in austral winter and a maximum in February-March. The FTIR and MAX-DOAS data are confronted with HCHO columns calculated by a global CTM, the IMAGES model. The model underestimates the HCHO columns by 23-29% in comparison with FTIR, and by 15% in comparison with DOAS. This bias might have multiple causes, including an underestimation of OH concentrations in the model (as indicated by a sensitivity study using prescribed OH fields) and/or an underestimated contribution of largescale transport of HCHO precursors from Madagascar. The latter hypothesis is comforted by the large observed day-today variability of HCHO columns, and by the observation that the peak values of FTIR columns can often be associated with free tropospheric transport patterns from source regions over Madagascar to Réunion Island, according to simulations performed with the Lagrangian particle dispersion model FLEXPART. [ABSTRACT FROM AUTHOR]

Ground-based high spectral resolution Fouriertransform 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 FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21° S, 55° E). These campaigns represent the first FTIR observations carried out at a southern (sub)tropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O3), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ethane (C2H6), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3) total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis) and at 2200m a.s.l. (Maïdo). It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinct altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT) measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer. [ABSTRACT FROM AUTHOR]

Abstract: This paper is the second of a series that reports results on the measurements of the absorption cross section of SO2 in the UV/visible region at high resolution and that investigates high temperatures in support to planetary applications. Absorption cross sections of SO2 have been obtained in the 29000–44000cm−1 spectral range (227–345nm) with a Fourier transform spectrometer at a resolution of 2cm−1 (0.4500cm MOPD and boxcar apodisation). Pure SO2 samples were used and measurements were performed at room temperature (298K) as well as at 318, 338 and 358K. Temperature effects in this spectral region are investigated and are favorably compared to existing studies in the literature. Comparison of the absorption cross section at room temperature shows good agreement in intensity with most of the literature data, but shows that most of the latter suffer from inaccurate wavelength scale definition. Moreover, literature data are often given only on restricted spectral intervals. Combined with the data described in the first part of this series of papers on SO2, this new data set offers the considerable advantage of covering the large spectral interval extending from 24000 to 44000cm−1 (227–420nm), at the four temperatures investigated. [Copyright &y& Elsevier]

Abstract: Absorption cross sections of SO2 have been obtained in the 24000–29000cm−1 spectral range (345–420nm) with a Fourier transform spectrometer at a resolution of 2cm−1. Pure SO2 samples were used and measurements were performed at room temperature (298K) as well as at 318, 338 and 358K. This is the first time that temperature effects in this spectral region are reported and investigated. This paper is the first of a series that will report on measurements of the absorption cross section of SO2 in the UV/visible region at a higher than previously reported resolution and that will investigate temperature effects in support of tropospheric, stratospheric and astrophysical or planetary applications. [Copyright &y& Elsevier]

The measurements of the NO2 absorption cross sections by several authors have been considered in order to derive its temperature and pressure dependences in the 13 200–42 000 cm−1 spectral range. The temperature dependence is assumed to be linear in the temperature range investigated (217.0–298.5 K), whereas the influence of the total pressure is expressed as a temperature-dependent broadening coefficient. From measurements performed with mixtures of NO2 in air and in N2, values of γair0 (296 K) and γN20 (296 K) were found to be, respectively, 0.081±0.002 and 0.069±0.003 cm−1 atm−1. The temperature coefficient n obtained in the present work is 0.8±0.1. The parameterization of the cross sections developed in this work can reproduce measured cross sections within 4%. [Copyright &y& Elsevier]

Abstract: Absorption spectra of HDO/D2O mixtures recorded in the 5600–8800cm−1 region with a total pressure of water from 13 up to 18hPa and an absorption path length of 600m have been analyzed in order to obtain new spectroscopic data for HD18O and D2 18O. In spite of the low natural 18O concentration (about 2×10−3 with respect to the 16O one), about 1100 transitions belonging to HD18O and more than 280 transitions belonging to D2 18O have been assigned. Most of the D2 18O transitions belong to the ν 1+ν 2+ν 3 and 2ν 1+ν 3 bands. Sets of energy levels for seven vibrational states of D2 18O and four states of HD18O are reported for the first time. The comparison of the experimental data with the calculated values based on Partridge–Schwenke global variational calculations is discussed. [ABSTRACT FROM AUTHOR]

Abstract: All available transitions from microwave to visible region (0.2–12 105cm−1) of the HD18O molecule were collected and tested using the RITZ computer code. Literature data were completed by transitions assigned to HD18O in long path Fourier transform absorption spectra of the H2O, HDO and D2O gas mixtures with natural abundance of oxygen-18. In addition about 40 unassigned lines between 4200 and 6600cm−1 of our previous water study associated with the HD18O molecule have been found and assigned. The new long path absorption spectra of the HDO and D2O mixtures allow us to observe about 1000 transitions of HD18O in the 6125–10720cm−1 spectral region. These data have been critically analyzed and used to obtain the most complete and precise set of the experimental energy levels of this molecule. [Copyright &y& Elsevier]

Abstract: Assignment of an HDO line list extracted from a recently measured H2O/HDO/D2O Fourier transform absorption spectrum recorded in the 11600–23000cm−1 region by Bach et al. (M. Bach, S. Fally, P.-F. Coheur, M. Carleer, A. Jenouvrier, A.C. Vandaele, J. Mol. Spectrosc. 232 (2005) 341–350.) is presented. More than 94% of the 3256 lines are given quantum number assignments and ascribed to line absorption by HDO; most of the remaining lines are actually due to D2O. High accuracy variational predictions of line positions and intensities are used for the spectral assignment process. Assignments to the ν 1 +5ν 3, 2ν 2 +5ν 3, ν 1 + ν 2 +3ν 3 and ν 1 +6ν 3 bands are presented for the first time. Comparisons are made with published ICLAS spectra covering the same spectral region and suggestions made for its recalibration. The results are used to illustrate the dynamical behaviour of highly excited vibrational states of HDO and to discuss previous vibrational assignments to high lying rotation–vibration states of this system. [Copyright &y& Elsevier]

Abstract: The absorption spectrum of dideuterated water, D2O, has been recorded between 8800 and 9520cm−1 by intracavity laser absorption spectroscopy (ICLAS) based on a vertical external cavity system emitting laser (VeCSEL) and by high sensitivity Fourier Transform spectroscopy. The combined analysis of the spectra has allowed attributing 1223 transitions to the D2O species. The spectrum assignment was performed on the basis of the recent results of variational calculations based on an optimized potential energy surface of D2O. A set of 687 energy levels was derived from transitions assigned to eight upper vibrational states, 577 of them being reported for the first time. A detailed line list has been generated. The line intensities were retrieved mainly from the FTS spectrum and the absolute integrated intensities of the 2v 1 + v 2 + v 3 and the v 2 +3v 3 bands dominating the spectrum have been determined. [Copyright &y& Elsevier]

The absorption spectra of the O(2) Herzberg band systems (A(3)Sigma(+)(u)-X(3)Sigma(-)(g), c(1)Sigma(-)(u)-X(3)Sigma(-)(g), and A' (3)Delta(u)-X(3)Sigma(-)(g)) lying in the wavelength region 240-300 nm were reinvestigated. The coupling of a long absorption cell and a high-resolution Fourier transform spectrometer has allowed the observation of numerous weak lines which were not reported previously. From the rotational analysis of the line positions, determined with an accuracy of 0.005 cm(-1), the molecular constants of the A(3)Sigma(+)(u), v = 0-12, c(1)Sigma(-)(u), v = 2-19, and A' (3)Delta(u), v = 2-12 levels are improved significantly. The interaction between the A and c states is described quantitatively. A new interpretation of the perturbations observed in the energy region close to the dissociation limit is given which involves a weakly bound (3)Pi(u) state as the most probable perturbing state. Copyright 1999 Academic Press.

Absorption spectroscopy, which is widely used for concentration measurements of tropospheric and stratospheric compounds, requires precise values of the absorption cross-sections of the measured species. NO(2), O(2) and its collision-induced absorption spectrum, and H(2)O absorption cross-sections have been measured at temperature and pressure conditions prevailing in the Earth's atmosphere. Corrections to the generally accepted analysis procedures used to resolve the convolution problem are also proposed.

Naturally occurring fogs in industrialized cities are contaminated by acidic air pollutants. In Brussels, Belgium, the pH of polluted fogwater may be as low as 3 with osmolarity as low as 30 mOsm. In order to explore short-term respiratory effects of a realistic acid-polluted fog, we collected samples of acid fog in Brussels, Belgium, which is a densely populated and industrialized city, we defined characteristics of this fog and exposed asthmatic volunteers at rest through a face mask to fogs with physical and chemical characteristics similar to those of natural fogs assessed in this urban area. Fogwater was sampled using a screen collector where droplets are collected by inertial impaction and chemical content of fogwater was assessed by measurement of conductivity, pH, visible colorimetry, high pressure liquid chromatography, and atomic absorption spectrophotometry over a period of one year. The fogwater composition was dominated by NH4+ and SO4- ions. First we evaluated the possible effect of fog acidity alone. For this purpose 14 subjects with asthma were exposed at rest for 1 hr [mass median aerodynamic diameter to a large-particle (MMAD), 9 microns] aerosol with H2SO4 concentration of 500 micrograms/m3 (pH 2.5) and osmolarity of 300 mOsm. We did not observe significant change in pulmonary function or bronchial responsiveness to metacholine. In the second part of the work, 10 asthmatic subjects were exposed to acid fog (MMAD, 7 microns) containing sulfate and ammonium ions (major ions recovered in naturally occurring fogs) with pH 3.5 and osmolarity 30 mOsm. Again, pulmonary function and bronchial reactivity were not modified after inhalation of this fog. It was concluded that short-term exposure to acid fog reproducing acidity and hypoosmolarity of natural polluted fogs does not induce bronchoconstriction and does not change bronchial responsiveness in asthmatics.