scholarly journals Diurnal variation of midlatitudinal NO<sub>3</sub> column abundance over Table Mountain Facility, California

2010 ◽  
Vol 10 (8) ◽  
pp. 20193-20237
Author(s):  
C. M. Chen ◽  
R. P. Cageao ◽  
L. Lawrence ◽  
J. Stutz ◽  
R. J. Salawitch ◽  
...  
Keyword(s):  
Full Moon ◽  
Optical Absorption Spectroscopy ◽  
Spectral Features ◽  
Free Troposphere ◽  
Absorption Bands ◽  
Model Calculations ◽  
Diurnal Variability ◽  
One Dimensional ◽  
Lunar Occultation ◽  
Table Mountain

Abstract. The column abundance of NO3 was measured over Table Mountain Facility, CA (34.4° N, 117.7° W) from May 2003 through September 2004, using lunar occultation near full moon with a grating spectrometer. The NO3 column retrieval was performed with the differential optical absorption spectroscopy (DOAS) technique using both the 623 and 662 nm NO3 absorption bands. Other spectral features such as Fraunhofer lines and absorption from water vapor and oxygen were removed using solar spectra obtained at different airmass factors. We observed a seasonal variation, with nocturnally averaged NO3 columns between 5–7×1013 molec cm−2 during October through March, and 5–22×1013 molec cm−2 during April through September. A subset of the data, with diurnal variability vastly different from the temporal profile obtained from one-dimensional stratospheric model calculations, clearly has boundary layer contributions; this was confirmed by simultaneous long-path DOAS measurements. However, even the NO3 columns that did follow the modeled time evolution were often much larger than modeled stratospheric partial columns constrained by realistic temperatures and ozone concentrations. This discrepancy is attributed to substantial tropospheric NO3 in the free troposphere, which may have the same time dependence as stratospheric NO3.

scholarly journals Diurnal variation of midlatitudinal NO<sub>3</sub> column abundance over table mountain facility, California

2011 ◽  
Vol 11 (3) ◽  
pp. 963-978 ◽  
Author(s):  
C. M. Chen ◽  
R. P. Cageao ◽  
L. Lawrence ◽  
J. Stutz ◽  
R. J. Salawitch ◽  
...  
Keyword(s):  
Full Moon ◽  
Optical Absorption Spectroscopy ◽  
Spectral Features ◽  
Free Troposphere ◽  
Absorption Bands ◽  
Model Calculations ◽  
Diurnal Variability ◽  
One Dimensional ◽  
Lunar Occultation ◽  
Table Mountain

Abstract. The column abundance of NO3 was measured over Table Mountain Facility, CA (34.4° N, 117.7° W) from May 2003 through September 2004, using lunar occultation near full moon with a grating spectrometer. The NO3 column retrieval was performed with the differential optical absorption spectroscopy (DOAS) technique using both the 623 and 662 nm NO3 absorption bands. Other spectral features such as Fraunhofer lines and absorption from water vapor and oxygen were removed using solar spectra obtained at different airmass factors. We observed a seasonal variation, with nocturnally averaged NO3 columns between 5−7 × 1013 molec cm−2 during October through March, and 5−22 × 1013 molec cm−2 during April through September. A subset of the data, with diurnal variability vastly different from the temporal profile obtained from one-dimensional stratospheric model calculations, clearly has boundary layer contributions; this was confirmed by simultaneous long-path DOAS measurements. However, even the NO3 columns that did follow the modeled time evolution were often much larger than modeled stratospheric partial columns constrained by realistic temperatures and ozone concentrations. This discrepancy is attributed to substantial tropospheric NO3 in the free troposphere, which may have the same time dependence as stratospheric NO3.

scholarly journals NO<sub>2</sub> seasonal evolution in the North Subtropical free troposphere

2015 ◽  
Vol 15 (10) ◽  
pp. 14473-14504
Author(s):  
M. Gil-Ojeda ◽  
M. Navarro-Comas ◽  
L. Gómez-Martín ◽  
J. A. Adame ◽  
A. Saiz-Lopez ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
High Mountain ◽  
Horizontal Line ◽  
Free Troposphere ◽  
Seasonal Evolution ◽  
The North ◽  
Measuring Period ◽  
The Impact ◽  
Pollution Events

Abstract. Three years of Multi-Axis Differential Optical Absorption Spectroscopy (MAXDOAS) measurements (2011–2013) have been used for estimating the NO2 mixing ratio along a horizontal line of sight from the high mountain Subtropical observatory of Izaña, at 2370 m a.s.l. (NDACC station, 28.3° N, 16.5° W). The method is based on horizontal path calculation from the O2–O2 collisional complex at the 477 nm absorption band which is measured simultaneously to the NO2, and is applicable under low aerosols loading conditions. The MAXDOAS technique, applied in horizontal mode in the free troposphere, minimizes the impact of the NO2 contamination resulting from the arrival of MBL airmasses from thermally forced upwelling breeze during central hours of the day. Comparisons with in-situ observations show that during most of measuring period the MAXDOAS is insensitive or very little sensitive to the upwelling breeze. Exceptions are found during pollution events under southern wind conditions. On these occasions, evidence of fast efficient and irreversible transport from the surface to the free troposphere is found. Background NO2 vmr, representative of the remote free troposphere, are in the range of 20–45 pptv. The observed seasonal evolution shows an annual wave where the peak is in phase with the solar radiation. Model simulations with the chemistry-climate CAM-Chem model are in good agreement with the NO2 measurements, and are used to further investigate the possible drivers of the NO2 seasonality observed at Izaña.

scholarly journals A broadband cavity ringdown spectrometer for in-situ measurements of atmospheric trace gases

2005 ◽  
Vol 5 (3) ◽  
pp. 3491-3532 ◽  
Author(s):  
M. Bitter ◽  
S. M. Ball ◽  
I. M. Povey ◽  
R. L. Jones
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Marine Boundary Layer ◽  
Thermal Dissociation ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Research Station ◽  
Absorption Bands ◽  
Optical Extinction ◽  
Cavity Ringdown

Abstract. This paper describes a broadband cavity ringdown spectrometer and its deployment during the 2002 North Atlantic Marine Boundary Layer Experiment (NAMBLEX) to measure ambient concentrations of NO3, N2O5, I2 and OIO at the Mace Head Atmospheric Research Station, Co. Galway, Ireland. The effective absorption path lengths accessible with the spectrometer generally exceeded 10 km, enabling sensitive localised ''point'' measurements of atmospheric absorbers to be made adjacent to the other instruments monitoring chemically related species at the same site. For the majority of observations, the spectrometer was used in an open path configuration thereby avoiding surface losses of reactive species. A subset of observations targeted the N2O5 molecule by detecting the additional NO3 formed by the thermal dissociation of N2O5. In all cases the concentrations of the atmospheric absorbers were retrieved by fitting the differential structure in the broadband cavity ringdown spectra using a methodology adapted from long path differential optical absorption spectroscopy. The uncertainty of the retrieval depends crucially on the correct treatment and fitting of the absorption bands due to water vapour, a topic that is discussed in the context of analysing broadband cavity ringdown spectra. The quality of the measurements and the retrieval method are illustrated with representative spectra acquired during NAMBLEX in spectral regions around 660 nm (NO3 and N2O5) and 570 nm (I2 and OIO). Typical detection limits were 1 pptv for NO3 in an integration time of 100 s, 4 pptv for OIO and 20 pptv for I2 in an integration time of 10 min. Additionally, the concentrations of atmospheric water vapour and the aerosol optical extinction were retrieved in both spectral regions. A companion paper in this issue presents the time series of the measurements and discusses their significance for understanding the variability of short lived nitrogen and iodine compounds in the marine boundary layer.

Characterization of Nanoclusters in MgO Created by Means of Ion Implantation.

2003 ◽  
Vol 792 ◽  
Author(s):  
M.A. van Huis ◽  
A. van Veen ◽  
H. Schut ◽  
B.J. Kooi ◽  
J.Th.M. De Hosson
Keyword(s):  
Optical Absorption ◽  
Ion Implantation ◽  
Noble Gas ◽  
Optical Absorption Spectroscopy ◽  
Metal Nanoclusters ◽  
Absorption Bands ◽  
Cross Sectional ◽  
Salt Structure ◽  
Scherrer Formula ◽  
Gas Clusters

ABSTRACTMetal nanoclusters (NCs) of lithium, zinc, silver and gold embedded in MgO were created by means of ion implantation of Li, Zn, Ag and Au ions into single crystals of MgO(100) and subsequent thermal annealing. Nanoclusters of the compound semiconductor CdSe were obtained by implantation of both Cd and Se ions. Solid noble gas clusters were formed by Kr ion implantation. Optical and structural properties of the NCs were investigated using optical absorption spectroscopy (OAS), high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The mean nanocluster size is estimated from the broadening of the Mie plasmon optical absorption bands using the Doyle formula. These results are compared with the NC size as obtained from XRD (using the Scherrer formula) and from direct XTEM observations. The three methods are found to be in reasonable agreement with a mean size of 4.0 and 10 nm found for the Au and Ag clusters, respectively. Using TEM observations, the relative interface energies of MgO//Au and MgO//Ag interfaces are also determined. In the case of MgO//Au, they are found not to be in agreement with theoretical predictions in the literature. CdSe nanoclusters were found to adopt different crystal structures dependent on the size. Small ones (<5 nm) appear to have a rock salt structure, larger ones the sphalerite structure. The solid krypton NC's are under high pressure. The pressure of individual Krypton bubbles was determined from the moiré fringes

scholarly journals Electron Dynamics in Anatase TiO2 Nanoparticles by Ultrafast Broadband Deep-Ultraviolet Spectroscopy

2019 ◽  
Vol 205 ◽  
pp. 05017
Author(s):  
Edoardo Baldini ◽  
Tania Palmieri ◽  
Enrico Pomarico ◽  
Gerald Auböck ◽  
Majed Chergui
Keyword(s):  
Lattice Dynamics ◽  
Anatase Tio2 ◽  
Spectral Features ◽  
Electron Dynamics ◽  
Electron Cooling ◽  
Absorption Bands ◽  
Bulk Absorption ◽  
Anatase Nanoparticles ◽  
Deep Ultraviolet ◽  
Broadband Spectroscopy

The optical bandgap of anatase TiO2 nanoparticles is dominated by bulk absorption bands in the deep-ultraviolet due to strongly bound excitons. These spectral features can be utilized as a sensitive probe of carrier and lattice dynamics inside the TiO2 nanoparticles. Here, we implement ultrafast broadband spectroscopy tuned to the exciton resonances in order to track the electron cooling in the conduction band of bare anatase nanoparticles and monitor the electron injection dynamics from an external dye in the case of sensitized anatase nanoparticles.

scholarly journals Quantitative Spectroscopy of Wolf-Rayet Stars

1988 ◽  
Vol 108 ◽  
pp. 133-140
Author(s):  
W. Schmutz
Keyword(s):  
Representative Point ◽  
Dimensional Model ◽  
Model Calculations ◽  
One Dimensional ◽  
The Past ◽  
First Results ◽  
The One ◽  
Expanding Atmospheres ◽  
New Generation ◽  
The Continuum

Advances in theoretical modeling of rapidly expanding atmospheres in the past few years made it possible to determine the stellar parameters of the Wolf-Rayet stars. This progress is mainly due to the improvement of the models with respect to their spatial extension: The new generation of models treat spherically-symmetric expanding atmospheres, i.e. the models are one-dimensional. Older models describe the wind by only one representative point. The older models are in fact ‘core-halo’ approximations. They have been introduced by Castor and van Blerkom (1970), and were extensively employed in the past (cf. e.g. Willis and Wilson, 1978; Smith and Willis, 1982). First results from new one-dimensional model calculations are published by Hillier (1984), Schmutz (1984), Hamann (1985), Hillier (1986), and Schmutz et al. (1987a); more detailed results are presented by Schmutz and Hamann (1986), Hamann and Schmutz (1987), Hillier (1987a,b), Wessolowski et al. (1987), Hillier (1987c) and Hamann et al. (1987). These results demonstrate that the step from zero- to one-dimensional calculations is essential. The important point is that the complicated interrelation between NLTE-level populations and radiation field is treated adequately (Schmutz and Hamann, 1986; Hillier, 1987). For this interrelation it is crucial to model consistently not only the line-formation region, but also the layers where the continuum is emitted. In fact, it is the core-halo approximation that causes the one-point models to fail in certain aspects.

A new photoluminescent coordination polymer constructed with an N-donor ligand having extended coordination capabilities derived from quinoline and pyridine

2020 ◽  
Vol 76 (5) ◽  
pp. 500-506
Author(s):  
Kamil Twaróg ◽  
Małgorzata Hołyńska ◽  
Andrzej Kochel
Keyword(s):  
Coordination Polymer ◽  
Pyridyl Ring ◽  
Ligand Molecule ◽  
Hydrothermal Conditions ◽  
Absorption Bands ◽  
Donor Ligand ◽  
One Dimensional ◽  
The One ◽  
Chloride Monohydrate ◽  
Carboxylic Acid Ligand

Employment of the organic 2-(pyridin-4-yl)quinoline-4-carboxylic acid ligand with extended coordination capabilities leads to the formation of the one-dimensional copper(II) coordination polymer catena-poly[[diaquacopper(II)]-bis[μ-2-(pyridin-4-yl)quinoline-4-carboxylato]-κ2 N 2:O;κ2 O:N], {[Cu(C15H9N2O2)2(H2O)2]·2H2O} n , under hydrothermal conditions. The ligand, isolated as its hydrochloride salt, namely, 4-(4-carboxyquinolin-2-yl)pyridinium chloride monohydrate, C15H11N2O2 +·Cl−·H2O, reveals a pseudosymmetry element (translation a/2) in its crystal structure. The additional pyridyl N atom, in comparison with the previously reported analogues with an arene ring instead of the pyridyl ring in the present ligand molecule, promotes the formation of a one-dimensional coordination polymer, rather than discrete molecules. This polymer shows photoluminescent properties with bathochromic/hypsochromic shifts of the ligand absorption bands, leading to a single band at 479 nm. The CuII ions are involved in weak antiferromagnetic interactions within dimeric units, as evidenced by SQUID magnetometry.

scholarly journals A climatological view of the vertical stratification of RH, O<sub>3</sub> and CO within the PBL and at the interface with free troposphere as seen by IAGOS aircraft and ozonesondes at northern mid-latitudes over 1994–2016

2018 ◽  
Author(s):  
Hervé Petetin ◽  
Bastien Sauvage ◽  
Herman G. J. Smit ◽  
François Gheusi ◽  
Fabienne Lohou ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Potential Temperature ◽  
Vertical Stratification ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Diurnal Variability ◽  
Vertical Coordinate ◽  
Mixing Ratios ◽  
Seasonal And Diurnal Variations ◽  
Individual Profiles

Abstract. This paper investigates in an innovative way the climatological vertical stratification of relative humidity (RH) and ozone (O3) and carbon monoxide (CO) mixing ratios within the planetary boundary layer (PBL) and at the interface with the free troposphere (FT). The climatology includes all vertical profiles available at northern mid-latitudes over the period 1994–2016 in both IAGOS (In-service Aircraft for a Global Observing System) and WOUDC (World Ozone and Ultraviolet Radiation Data Centre) databases, which represents more than 90,000 vertical profiles. For all individual profiles, apart from the specific case of surface-based temperature inversions (SBIs), the PBL height is estimated following the elevated temperature inversion (EI) method. Several features of both SBIs and EIs are analysed, including their diurnal and seasonal variations. Based on these PBL height estimates (denoted h), the original approach introduced in this paper consists in building a so-called PBL-referenced vertical distribution of O3, CO and RH by averaging all individual profiles beforehand expressed as a function of z/h rather than z (with z the altitude). Using this vertical coordinate system allows to highlight the features existing at the PBL-FT interface that would have been smoothed otherwise. Results demonstrate that the frequently assumed well-mixed PBL remains an exception for both chemical species. Within the PBL, CO profiles are characterized by a mean vertical stratification (here defined as the standard deviation of the CO profile between the surface and the PBL top, normalized by the mean) of 11 %, with moderate seasonal and diurnal variations. A higher vertical stratification is observed for O3 mixing ratios (18 %), with stronger seasonal and diurnal variability (from ~ 10 % in spring/summer midday/afternoon to ~ 25 % in winter/fall night). This vertical stratification is distributed heterogeneously in the PBL with stronger vertical gradients observed at both the surface (due to dry deposition and titration by NO for O3; and due to surface emissions for CO) and the PBL-FT interface. These gradients vary with the season from lowest values in summer to highest ones in winter. Contrary to CO, the O3 vertical stratification was found to vary with the surface potential temperature following an interesting bell shape with weakest stratification for both lowest (typically negative) and highest temperatures, which could be due to a much lower O3 dry deposition under the presence of snow. Therefore, results demonstrate that EIs act as a geophysical interface separating air masses of distinct chemical composition and/or chemical regime. This is further supported by the analysis of the correlation of O3 and CO mixing ratios between the different altitude levels in the PBL and FT (the so-called vertical autocorrelation). Results indeed highlight lower correlations apart from the PBL-FT interface and higher correlations within each of the two atmospheric compartments (PBL and FT).

scholarly journals The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared – Part 2: Accurate calibration of high spectral-resolution infrared measurements of surface solar radiation

2016 ◽  
Vol 9 (9) ◽  
pp. 4673-4686 ◽  
Author(s):  
Andreas Reichert ◽  
Markus Rettinger ◽  
Ralf Sussmann
Keyword(s):  
Water Vapor ◽  
Spectral Range ◽  
High Spectral Resolution ◽  
Spectral Radiance ◽  
Transfer Model ◽  
Water Vapor Absorption ◽  
Absorption Bands ◽  
Model Calculations ◽  
Infrared Measurements ◽  
Vapor Absorption

Abstract. Quantitative knowledge of water vapor absorption is crucial for accurate climate simulations. An open science question in this context concerns the strength of the water vapor continuum in the near infrared (NIR) at atmospheric temperatures, which is still to be quantified by measurements. This issue can be addressed with radiative closure experiments using solar absorption spectra. However, the spectra used for water vapor continuum quantification have to be radiometrically calibrated. We present for the first time a method that yields sufficient calibration accuracy for NIR water vapor continuum quantification in an atmospheric closure experiment. Our method combines the Langley method with spectral radiance measurements of a high-temperature blackbody calibration source (<  2000 K). The calibration scheme is demonstrated in the spectral range 2500 to 7800 cm−1, but minor modifications to the method enable calibration also throughout the remainder of the NIR spectral range. The resulting uncertainty (2σ) excluding the contribution due to inaccuracies in the extra-atmospheric solar spectrum (ESS) is below 1 % in window regions and up to 1.7 % within absorption bands. The overall radiometric accuracy of the calibration depends on the ESS uncertainty, on which at present no firm consensus has been reached in the NIR. However, as is shown in the companion publication Reichert and Sussmann (2016), ESS uncertainty is only of minor importance for the specific aim of this study, i.e., the quantification of the water vapor continuum in a closure experiment. The calibration uncertainty estimate is substantiated by the investigation of calibration self-consistency, which yields compatible results within the estimated errors for 91.1 % of the 2500 to 7800 cm−1 range. Additionally, a comparison of a set of calibrated spectra to radiative transfer model calculations yields consistent results within the estimated errors for 97.7 % of the spectral range.

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

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