Author Institution: Laboratoire de Physique Moleculaire et Atmospherique, Universit{\'e} Pierre et Marie Curie et C. N. R. S.; Atmospheric Sciences Division, NASA Langley Research Center; Department of Physics, College of William and Mary
Ammonia (NH 3 ) is a reactive air pollutant strongly affecting both environment and human health. Massive industrial production of ammonia and the development of crops enhancing biological nitrogen fixation disturb the natural cycle and contribute to eutrophication, loss of biodiversity and acidification of various environments (soils, lakes, streams, etc.) (Galloway et al., 2003). Within the troposphere, NH 3 can react with SO 2 or HNO 3 to produce fine particulate matter (PM2.5) of ammonium salts (Behera et al., 2013). Thus, measuring atmospheric ammonia is necessary to better constraint particulate matter formation and reactive nitrogen budgets in air quality models.
In the present study, we use the mid-resolution OASIS (Observations of the Atmosphere by Solar absorption Infrared Spectroscopy) ground-based FTIR solar observatory (Viatte et al., 2011 ; Chelin et al., 2015) to derive ammonia total columns over Paris suburbs (Creteil, 48.79°N, 2.44°E, France) using the PROFFIT inversion code (Hase et al., 2004). Thus, we have obtained the first multi-year time series of NH 3 ground-based measurements in Paris region (2009-2016).
We analyze diurnal and seasonal variabilities of NH3 and study the relationship with meteorological variables. We also compare NH 3 total columns derived from OASIS and those from IASI satellite measurements (Whitburn et al., 2016).
The first atmospheric profiles of the ultraviolet/visible (UV/vis) absorption bands of the collision complex O 2 ‐O 2 , or O 4 in brief, are reported. The O 4 absorption profiles are inferred from direct Sun spectra observed from the LPMA/DOAS (Laboratoire Physique Moléculaire et Application/Differential Optical Absorption Spectroscopy) balloon gondola. Seven O 4 absorption bands ‐ centered at ∼360.7, 380.2, 446.7, 477.1, 532.2, 577.2, and 630.0 nm ‐ are investigated for atmospheric pressures ( p ) ranging from ∼500 hPa to ∼40 hPa and temperatures ( T ) ranging from 203 K to 250 K. For the encountered atmospheric conditions, it is found that, (a) the band shapes do not change with T and p and (b) the peak collision pair absorption intensities (α i ) concurrently increase with decreasing T (by about 11 % over a Δ T =50 K). That result is in agreement with previous laboratory O 4 studies mostly conducted at high O 2 partial pressures (up to several hundred bars). Furthermore, by reasonably assuming that the O 4 absorption cross sections are T‐independent, the inferred T‐dependence of α i ( T ) suggests a thermally averaged enthalpy change < Δ H > = −(1207±83) J/Mol involved in the formation of O 4 . Our inferred Δ H is in reasonable agreement with the orientation and spin averaged O 4 well depth De(O 4 ) (= ‐(1130±80) J/Mol) measured in a recent O 2 ‐O 2 collision experiment, when accounting for the rovibrational energy change during O 4 formation (186 J/Mol).
Abstract. Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7) in the visible spectral range (415-650 nm), but it is +2.1% larger in the (370-415 nm) wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b) and SORCE/SIM (Harder et al., 2000) solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen -) with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm), -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.
