Keynotes

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Analysis of an 18O and D enhanced water spectrum and new assignments for HD18O and D218O in the near-infrared region (6000–7000 cm−1) using newly calculated variational line lists

An experimental infrared spectrum due to Orphal and Ruth (2008) [10] recorded using isotopically enriched water in the 6000–7000 cm−1 region is analysed and assigned. The assignment procedure is based on the use of known transition frequencies for H216O and H218O, existing variational line lists for HD16O and D216O, and newly calculated variational line lists for HD18O and D218O. These new variational line lists are presented herein. The main absorption comes from HD16O and HD18O, for which there are few previous assignments in the region. Assignments to 426 new HD18O lines are presented. In all 3254 of the 4768 lines observed in the spectrum are assigned, resulting in a number of newly determined energy levels. These assignments are in agreement with the recent work of Mikhailenko et al. (2012) [41]

The CO2 –broadened H2O continuum in the 100–1500 cm -1 region: Measurements, predictions and empirical model

Transmission spectra of H2O + CO2 mixtures have been recorded, at 296, 325 and 366 K, for various pres- sures and mixture compositions using two experimental setups. Their analysis enables to retrieve values of the “continuum”absorption by the CO2 -broadened H2O line wings between 100 and 1500 cm-1 . The results are in good agreement with those, around 1300 cm-1 , of the single previous experimental study available. Comparisons are also made with direct predictions based on line-shape correction factors χ calculated, almost thirty years ago, using a quasistatic approach and an input H2O –CO2 intermolecular potential. They show that this model quite nicely predicts, with slightly overestimated values, the con- tinuum over a spectral range where it varies by more than three orders of magnitude. An empirical cor- rection is proposed, based on the experimental data, which should be useful for radiative transfer and climate studies in CO2 rich planetary atmospheres

Étude des propriétés radiatives de la vapeur d'eau à haute température et haute pression par diagnostic optique de la combustion H2/02/N2

NANTERRE-BU PARIS10 (920502102) / SudocSudocFranceF

Line profile study by diode laser spectroscopy in the 12CH 4 ν2 + ν4 band

We present a complete study on four methane lines for two atmospheric micro-windows (in the ν2 + ν4 absorption band) used for the determination of atmospheric methane concentrations with ground-based Fourier transform spectrometers. Thanks to our tunable diode laser (TDL) spectrometer with active wavenumber control and step-by-step recording mode we have improved the accuracy on intensity, broadening, narrowing, and pressure shift parameters. To make our results directly useable in atmospheric models which usually assume a Voigt line shape, we have parameterised an effective-broadening parameter γVoigt (P) for each line and each gas mixture (CH4-N2 and CH4-O 2). When this parameterisation is used to fit a "true" line profile, the same concentration as with more sophisticated models is retrieved using a consistent set of spectroscopic parameters in both approaches. © 2005 Elsevier Inc. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Analysis of the diurnal evolution of atmospheric ammonia over the Paris megacity from ground-based and satellite remote sensing

International audienceEcosystems and human health are directly affected by atmospheric ammonia, by unbalancing the vegetation nutrient cycle and causing respiratory troubles both directly and through the formation of fine particles. In Europe, agricultural practices are the dominant source of atmospheric ammonia. It is released to the atmosphere by volatilization of fertilizer applied to soils and decay of organic matter. Then, it reacts with acids (such as sulphuric, nitric and chlorine acids) or nitrogen oxides (all produced in high concentrations from anthropogenic activities) to produce ammonium aerosols, whose concentrations over Europe and Paris megacity are particularly high during springtime pollution events, as occurred in 2014 and 2015.Difficulties for measuring ammonia by in situ techniques are induced by its polarity, which causes accumulation in inlets and sampling tubes. Remote sensing is therefore a valuable alternative method to measure ammonia, without direct interaction with the sample. Measurements of ammonia total atmospheric columns using the OASIS observatory are routinely made in the Paris suburbs since 2009 using a medium spectral resolution BRUKER Fourier transform infrared spectrometer. Spectra of radiation emitted by the sun and absorbed by the atmosphere were recorded every 10 minutes, under clear sky conditions, enabling the observation of the diurnal evolution of ammonia concentrations.Our work provides a new analyse of the diurnal evolution of ammonia over the Paris megacity during springtime pollution events. For this, we use measurements of total atmospheric columns of ammonia derived from the ground-based OASIS observatory for the first time and from satellite approaches, such as that from IASI and other available satellites. Furthermore, this study takes into account the influence of meteorological conditions and atmospheric chemical composition, of gaseous and particulate phases, from surface measurements simultaneously performed at Palaiseau, in the Paris region

Atmospheric ammonia (NH₃) over the Paris megacity: 9 years of total column observations from ground-based infrared remote sensing

International audienceIn this paper, we present the first multi-year time series of atmospheric NH3 ground-based measurements in the Paris region (Créteil, 48.79° N, 2.44° E, France) retrieved with the mid-resolution “Observations of the Atmosphere by Solar absorption Infrared Spectroscopy” (OASIS) ground-based Fourier Transform infrared solar observatory. Located in an urban region, OASIS has previously been used for monitoring air quality (tropospheric ozone and carbon monoxide), thanks to its specific column sensitivity across the whole troposphere including the planetary boundary layer. A total of 4920 measurements of atmospheric total columns of ammonia have been obtained from 2009 to 2017, with uncertainties ranging from 20 % to 35 %, and are compared with NH3 concentrations derived from the Infrared Atmospheric Sounding Interferometer (IASI). OASIS ground-based measurements show significant interannual, and seasonal variabilities of atmospheric ammonia. NH3 total columns over the Paris megacity (12 million people) vary seasonally by 2 orders of magnitude, from approximately 1015 molecules cm−2 in winter to 1017 molecules cm−2 for spring peaks, probably due to springtime spreading of fertilizers on surrounding croplands. Also, we observe a correlation of daily NH3-OASIS total columns with daily PM2.5 in situ measurements from the closest Airparif surface station in springtime