scholarly journals Development and recent evaluation of the MT_CKD model of continuum absorption

2012 ◽  
Vol 370 (1968) ◽  
pp. 2520-2556 ◽  
Author(s):  
Eli J. Mlawer ◽  
Vivienne H. Payne ◽  
Jean-Luc Moncet ◽  
Jennifer S. Delamere ◽  
Matthew J. Alvarado ◽  
...  
Keyword(s):  
Water Vapour ◽  
Line Shape ◽  
Mathematical Formulation ◽  
Field Measurements ◽  
Continuum Absorption ◽  
Semi Empirical ◽  
Vapour Molecule ◽  
Primary Agent ◽  
The Continuum

Water vapour continuum absorption is an important contributor to the Earth's radiative cooling and energy balance. Here, we describe the development and status of the MT_CKD (MlawerTobinCloughKneizysDavies) water vapour continuum absorption model. The perspective adopted in developing the MT_CKD model has been to constrain the model so that it is consistent with quality analyses of spectral atmospheric and laboratory measurements of the foreign and self continuum. For field measurements, only cases for which the characterization of the atmospheric state has been highly scrutinized have been used. Continuum coefficients in spectral regions that have not been subject to compelling analyses are determined by a mathematical formulation of the spectral shape associated with each water vapour monomer line. This formulation, which is based on continuum values in spectral regions in which the coefficients are well constrained by measurements, is applied consistently to all water vapour monomer lines from the microwave to the visible. The results are summed-up (separately for the foreign and self) to obtain continuum coefficients from 0 to 20 000 cm −1 . For each water vapour line, the MT_CKD line shape formulation consists of two components: exponentially decaying far wings of the line plus a contribution from a water vapour molecule undergoing a weak interaction with a second molecule. In the MT_CKD model, the first component is the primary agent for the continuum between water vapour bands, while the second component is responsible for the majority of the continuum within water vapour bands. The MT_CKD model should be regarded as a semi-empirical model with strong constraints provided by the known physics. Keeping the MT_CKD continuum consistent with current observational studies necessitates periodic updates to the water vapour continuum coefficients. In addition to providing details on the MT_CKD line shape formulation, we describe the most recent update to the model, MT_CKD_2.5, which is based on an analysis of satellite- and ground-based observations from 2385 to 2600 cm −1 (approx. 4 μm).

scholarly journals Airborne and satellite remote sensing of the mid-infrared water vapour continuum

2012 ◽  
Vol 370 (1968) ◽  
pp. 2611-2636 ◽  
Author(s):  
Stuart M. Newman ◽  
Paul D. Green ◽  
Igor V. Ptashnik ◽  
Tom D. Gardiner ◽  
Marc D. Coleman ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Vapour ◽  
Weather Forecasting ◽  
Field Measurements ◽  
Atmospheric Models ◽  
Atmospheric Measurements ◽  
Continuum Absorption ◽  
Infrared Radiance ◽  
Research Aircraft ◽  
Absorption Field

Remote sensing of the atmosphere from space plays an increasingly important role in weather forecasting. Exploiting observations from the latest generation of weather satellites relies on an accurate knowledge of fundamental spectroscopy, including the water vapour continuum absorption. Field campaigns involving the Facility for Airborne Atmospheric Measurements research aircraft have collected a comprehensive dataset, comprising remotely sensed infrared radiance observations collocated with accurate measurements of the temperature and humidity structure of the atmosphere. These field measurements have been used to validate the strength of the infrared water vapour continuum in comparison with the latest laboratory measurements. The recent substantial changes to self-continuum coefficients in the widely used MT_CKD (Mlawer–Tobin–Clough–Kneizys–Davies) model between 2400 and 3200 cm −1 are shown to be appropriate and in agreement with field measurements. Results for the foreign continuum in the 1300–2000 cm −1 band suggest a weak temperature dependence that is not currently included in atmospheric models. A one-dimensional variational retrieval experiment is performed that shows a small positive benefit from using new laboratory-derived continuum coefficients for humidity retrievals.

Absolute high spectral resolution measurements of surface solar radiation for detection of water vapour continuum absorption

2012 ◽  
Vol 370 (1968) ◽  
pp. 2590-2610 ◽  
Author(s):  
T. D. Gardiner ◽  
M. Coleman ◽  
H. Browning ◽  
L. Tallis ◽  
I. V. Ptashnik ◽  
...  
Keyword(s):  
Water Vapour ◽  
Field Measurements ◽  
Solar Irradiation ◽  
High Spectral Resolution ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Spectral Structure ◽  
Atmospheric Transmission ◽  
Surface Solar Radiation ◽  
Continuum Absorption

Solar-pointing Fourier transform infrared (FTIR) spectroscopy offers the capability to measure both the fine scale and broadband spectral structure of atmospheric transmission simultaneously across wide spectral regions. It is therefore suited to the study of both water vapour monomer and continuum absorption behaviours. However, in order to properly address this issue, it is necessary to radiatively calibrate the FTIR instrument response. A solar-pointing high-resolution FTIR spectrometer was deployed as part of the ‘Continuum Absorption by Visible and Infrared radiation and its Atmospheric Relevance’ (CAVIAR) consortium project. This paper describes the radiative calibration process using an ultra-high-temperature blackbody and the consideration of the related influence factors. The result is a radiatively calibrated measurement of the solar irradiation at the ground across the IR region from 2000 to 10 000 cm −1 with an uncertainty of between 3.3 and 5.9 per cent. This measurement is shown to be in good general agreement with a radiative-transfer model. The results from the CAVIAR field measurements are being used in ongoing studies of atmospheric absorbers, in particular the water vapour continuum.

scholarly journals The Thermal and Magnetic Structure of Sunspots

1994 ◽  
Vol 154 ◽  
pp. 423-435
Author(s):  
P. Maltby
Keyword(s):  
Magnetic Field ◽  
High Spatial Resolution ◽  
Field Measurements ◽  
High Accuracy ◽  
Infrared Observations ◽  
Large Fluctuations ◽  
Magnetic Field Measurements ◽  
Semi Empirical ◽  
The Continuum ◽  
Field Inclination

The continuum intensity observations of sunspot umbrae and penumbrae in the visible and infrared are reviewed. The intensity in the darkest part of the umbra and the average penumbral intensity are known with relatively high accuracy in large sunspots. The importance of including infrared observations in the construction of semi-empirical sunspot models is emphasized.Magnetic field measurements are discussed. Special attention is given to recent high-spatial-resolution observations that show large fluctuations in magnetic field inclination, suggesting that the sunspot magnetic field changes its inclination – but not its magnitude – between bright and dark penumbral features.

scholarly journals The water vapour self- and water–nitrogen continuum absorption in the 1000 and 2500 cm −1 atmospheric windows

2012 ◽  
Vol 370 (1968) ◽  
pp. 2578-2589 ◽  
Author(s):  
Yu. I. Baranov ◽  
W. J. Lafferty
Keyword(s):  
Experimental Data ◽  
Water Vapour ◽  
Continuum Model ◽  
Pure Water ◽  
Laboratory Data ◽  
The Other ◽  
Continuum Absorption ◽  
Infrared Spectrometer ◽  
Atmospheric Windows ◽  
The Continuum

The pure water vapour and water–nitrogen continuum absorption in the 1000 and 2500 cm −1 atmospheric windows has been studied using a 2 m base-length White-type multi-pass cell coupled with a BOMEM DA3-002 Fourier transform infrared spectrometer. The measurements were carried out at the National Institute of Standards and Technology (NIST, Gaithersburg, MD) over the course of several years (2004, 2006–2007, 2009). New data on the H 2 O:N 2 continuum in the 1000 cm −1 window are presented and summarized along with the other experimental results and the continuum model. The experimental data reported on the water vapour continuum in these atmospheric windows basically agree with the most reliable laboratory data from the other sources. The MT_CKD (MlawerTobinCloughKneizysDavies) continuum model significantly departs from the experimental data in both windows. The deviation observed includes the continuum magnitude, spectral behaviour and temperature dependence. In the 2500 cm −1 region, the model does not allow for the nitrogen fundamental collision-induced absorption (CIA) band intensity enhancement caused by H 2 O:N 2 collisions and underestimates the actual absorption by over two orders of magnitude. The water vapour continuum interpretation as a typical CIA spectrum is reviewed and discussed.

scholarly journals Recent advances in measurement of the water vapour continuum in the far-infrared spectral region

2012 ◽  
Vol 370 (1968) ◽  
pp. 2637-2655 ◽  
Author(s):  
Paul D. Green ◽  
Stuart M. Newman ◽  
Ralph J. Beeby ◽  
Jonathan E. Murray ◽  
Juliet C. Pickering ◽  
...  
Keyword(s):  
Water Vapour ◽  
Spectral Band ◽  
Far Infrared ◽  
Ir Radiation ◽  
Continuum Absorption ◽  
Pure Rotation ◽  
Wide Range ◽  
Infrared Spectral ◽  
Research Aircraft ◽  
The Continuum

We present a new derivation of the foreign-broadened water vapour continuum in the far-infrared (far-IR) pure rotation band between 24 μm and 120 μm (85–420 cm −1 ) from field data collected in flight campaigns of the Continuum Absorption by Visible and IR radiation and Atmospheric Relevance (CAVIAR) project with Imperial College's Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) far-IR spectro-radiometer instrument onboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft; and compare this new derivation with those recently published in the literature in this spectral band. This new dataset validates the current Mlawer–Tobin-Clough–Kneizys–Davies (MT-CKD) 2.5 model parametrization above 300 cm −1 , but indicates the need to strengthen the parametrization below 300 cm −1 , by up to 50 per cent at 100 cm −1 . Data recorded at a number of flight altitudes have allowed measurements within a wide range of column water vapour environments, greatly increasing the sensitivity of this analysis to the continuum strength.

Ionized gas kinematics and luminosity profiles of Low-z Lyman Alpha Blobs

2019 ◽  
Vol 15 (S359) ◽  
pp. 413-414
Author(s):  
María P. Agüero ◽  
Rubén Díaz ◽  
Mischa Schirmer
Keyword(s):  
Emission Line ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Lyman Alpha ◽  
Gas Kinematics ◽  
The Universe ◽  
Very High ◽  
The Continuum

AbstractThis work is focused on the characterization of the Seyfert-2 galaxies hosting very large, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2−0.34. With a space density of 4.4 Gcp−3 at z ∼ 0.3, these “Low Redshift Lyman-α Blob” (LAB) host galaxies are amongst the rarest objects in the universe, and represent an exceptional and short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). We present the study of GMOS spectra for 13 LAB galaxies covering the rest frame spectral range 3700–6700 Å. Predominantly, the [OIII]λ5007 emission line radial distribution is as widespread as that of the continuum one. The emission line profiles exhibit FWHM between 300–700 Km s−1. In 7 of 13 cases a broad kinematical component is detected with FWHM within the range 600–1100 Km s−1. The exceptionally high [OIII]λ5007 luminosity is responsible for very high equivalent width reaching 1500 Å at the nucleus.

scholarly journals Pressure effects on water vapour lines: beyond the Voigt profile

2012 ◽  
Vol 370 (1968) ◽  
pp. 2495-2508 ◽  
Author(s):  
N. H. Ngo ◽  
H. Tran ◽  
R. R. Gamache ◽  
J. M. Hartmann
Keyword(s):  
Water Vapour ◽  
Line Shape ◽  
Pressure Effects ◽  
Shape Model ◽  
Line Shapes ◽  
Voigt Profile ◽  
Voigt Model ◽  
Velocity Changes ◽  
Dynamics Simulations ◽  
Induced Velocity

A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H 2 O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm −1 atm −1 ) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking ‘velocity effects’ into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from ‘first principles’, are discussed.

Relation between Magnetic, Spectroscopic and Structural Properties of Binuclear Copper(II) Complexes of Pentadentate Schiff-base Ligand, Semi-empirical and ab-initio Calculations

2003 ◽  
Vol 58 (5-6) ◽  
pp. 363-372 ◽  
Author(s):  
Y. Elerman ◽  
H. Kara ◽  
A. Elmali
Keyword(s):  
Ab Initio ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Hartree Fock ◽  
Ligand Orbital ◽  
Rhf Calculations ◽  
The Difference ◽  
Semi Empirical

The synthesis and characterization of [Cu2(L1)(3,5 prz)] (L1=1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino) propan-2-ol) 1 and of [Cu2(L2)(3,5 prz)] (L2=1,3-Bis(2-hydroxy-bromosalicylideneamino) propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu2(L1)(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperaturedependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm−1 for 1 and 440 cm−1 for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Hückel Molecular Orbital (EHMO) calculations are also reported.

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