scholarly journals Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

2015 ◽  
Vol 11 (3) ◽  
pp. 1985-2007
Author(s):  
R. V. Kochanov ◽  
I. E. Gordon ◽  
L. S. Rothman ◽  
S. W. Sharpe ◽  
T. J. Johnson ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Cross Sections ◽  
Spectral Region ◽  
Radiative Forcing ◽  
Recent Article ◽  
The Other ◽  
Radiative Forcings ◽  
The Status ◽  
Moderate Resolution ◽  
Spectroscopic Database

Abstract. In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases," Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm−1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases does a modest discrepancy exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10%, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors have affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 + NO2 dimer was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly.

scholarly journals Comment on "Radiative forcings for 28 potential Archean greenhouse gases" by Byrne and Goldblatt (2014)

2015 ◽  
Vol 11 (8) ◽  
pp. 1097-1105 ◽  
Author(s):  
R. V. Kochanov ◽  
I. E. Gordon ◽  
L. S. Rothman ◽  
S. W. Sharpe ◽  
T. J. Johnson ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Cross Sections ◽  
Spectral Region ◽  
Radiative Forcing ◽  
Recent Article ◽  
The Other ◽  
Radiative Forcings ◽  
The Status ◽  
Moderate Resolution ◽  
Spectroscopic Database

Abstract. In the recent article by Byrne and Goldblatt, "Radiative forcing for 28 potential Archean greenhouse gases", Clim. Past. 10, 1779–1801 (2014), the authors employ the HITRAN2012 spectroscopic database to evaluate the radiative forcing of 28 Archean gases. As part of the evaluation of the status of the spectroscopy of these gases in the selected spectral region (50–1800 cm−1), the cross sections generated from the HITRAN line-by-line parameters were compared with those of the PNNL database of experimental cross sections recorded at moderate resolution. The authors claimed that for NO2, HNO3, H2CO, H2O2, HCOOH, C2H4, CH3OH and CH3Br there exist large or sometimes severe disagreements between the databases. In this work we show that for only three of these eight gases a modest discrepancy does exist between the two databases and we explain the origin of the differences. For the other five gases, the disagreements are not nearly at the scale suggested by the authors, while we explain some of the differences that do exist. In summary, the agreement between the HITRAN and PNNL databases is very good, although not perfect. Typically differences do not exceed 10 %, provided that HITRAN data exist for the bands/wavelengths of interest. It appears that a molecule-dependent combination of errors has affected the conclusions of the authors. In at least one case it appears that they did not take the correct file from PNNL (N2O4 (dimer)+ NO2 was used in place of the monomer). Finally, cross sections of HO2 from HITRAN (which do not have a PNNL counterpart) were not calculated correctly in BG, while in the case of HF misleading discussion was presented there based on the confusion by foreign or noise features in the experimental PNNL spectra.

scholarly journals Radiative forcings for 28 potential Archean greenhouse gases

2014 ◽  
Vol 10 (3) ◽  
pp. 2011-2053 ◽  
Author(s):  
B. Byrne ◽  
C. Goldblatt
Keyword(s):  
Greenhouse Gases ◽  
Atmospheric Pressure ◽  
Radiative Forcing ◽  
Near Infrared ◽  
High Accuracy ◽  
The Other ◽  
Hitran Database ◽  
Warm Climate ◽  
Radiative Forcings ◽  
Standard Set

Abstract. Despite reduced insolation in the late Archean, evidence suggests a warm climate which was likely sustained by a stronger greenhouse effect, the so-called Faint Young Sun Problem (FYSP). CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4 and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data for background pressures of 0.5, 1, and 2 bar. For CO2 to resolve the FYSP alone, 0.21 bar is needed with 0.5 bar of atmospheric pressure, 0.13 bar with 1 bar of atmospheric pressures, or 0.07 bar with 2 bar of atmospheric pressure. For CH4, we find that near-infrared absorption is much stronger than previously thought, arising from updates to the HITRAN database. CH4 radiative forcing peaks at 10.3, 9, or 8.3 W m−2 for background pressures of 0.5, 1 or 2 bar, likely limiting the utility of CH4 for warming the Archean. For the other 26 HITRAN gases, radiative forcings of up to a few to 10 W m−2 are obtained from concentrations of 0.1–1 ppmv for many gases. We further calculate the reduction of radiative forcing due to gas overlap for the 20 strongest gases. We recommend the forcings provided here be used both as a first reference for which gases are likely good greenhouse gases, and as a standard set of calculations for validation of radiative forcing calculations for the Archean.

scholarly journals Radiative forcings for 28 potential Archean greenhouse gases

2014 ◽  
Vol 10 (5) ◽  
pp. 1779-1801 ◽  
Author(s):  
B. Byrne ◽  
C. Goldblatt
Keyword(s):  
Greenhouse Gases ◽  
Infrared Absorption ◽  
Radiative Forcing ◽  
Near Infrared ◽  
High Accuracy ◽  
The Other ◽  
Hitran Database ◽  
Warm Climate ◽  
Radiative Forcings ◽  
Standard Set

Abstract. Despite reduced insolation in the late Archean, evidence suggests a~warm climate which was likely sustained by a stronger greenhouse effect, the so-called faint young sun problem (FYSP). CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4, and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data for background pressures of 0.5, 1, and 2 bar of atmospheric N2. For CO2 to resolve the FYSP alone at 2.8 Gyr BP (80% of present solar luminosity), 0.32 bar is needed with 0.5 bar of atmospheric N2, 0.20 bar with 1 bar of atmospheric N2, or 0.11 bar with 2 bar of atmospheric N2. For CH4, we find that near-infrared absorption is much stronger than previously thought, arising from updates to the HITRAN database. CH4 radiative forcing peaks at 10.3, 9, or 8.3 W m−2 for background pressures of 0.5, 1, or 2 bar, likely limiting the utility of CH4 for warming the Archean. For the other 26 HITRAN gases, radiative forcings of up to a few to 10 W m−2 are obtained from concentrations of 0.1–1 ppmv for many gases. For the 20 strongest gases, we calculate the reduction in radiative forcing due to overlap. We also tabulate the modern sources, sinks, concentrations, and lifetimes of these gases and summaries the literature on Archean sources and concentrations. We recommend the forcings provided here be used both as a first reference for which gases are likely good greenhouse gases, and as a standard set of calculations for validation of radiative forcing calculations for the Archean.

scholarly journals Atmospheric Lifetimes, Infrared Absorption Spectra, Radiative Forcings and Global Warming Potentials of NF<sub>3</sub> and CFC-115

2016 ◽  
Author(s):  
Anna Totterdill ◽  
Tamás Kovács ◽  
Wuhu Feng ◽  
Sandip Dhomse ◽  
Christopher J. Smith ◽  
...  
Keyword(s):  
Global Warming ◽  
Cross Sections ◽  
Infrared Absorption ◽  
Radiative Forcing ◽  
Climate Model ◽  
Radiative Forcings ◽  
Atmospheric Window ◽  
Infrared Absorption Spectra ◽  
Global Warming Potentials ◽  
Good Agreement

Abstract. Fluorinated compounds such as NF3 and C2F5Cl (CFC-115) are characterised by very large global warming potentials (GWPs) which result from extremely long atmospheric lifetimes and strong infrared absorptions in the atmospheric window. In this study we have experimentally determined the infrared absorption cross-sections of NF3 and CFC-115, calculated the radiative forcing and efficiency using two radiative transfer models and identified the effect of clouds and stratospheric adjustment. The infrared cross sections are in good agreement with previous measurements, whereas the resulting radiative forcings and efficiencies are, on average, around 10 % larger. A whole atmosphere chemistry-climate model was used to determine the atmospheric lifetimes of NF3 and CFC-115 to be (616 ± 34) years and (492 ± 22) years, respectively. The GWPs for NF3 are estimated to be 14 600, 19 400 and 21 400 over 20, 100 and 500 years, respectively. Similarly, the GWPs for CFC-115 are 6120, 8060 and 8630 over 20, 100 and 500 years, respectively.

scholarly journals Atmospheric lifetimes, infrared absorption spectra, radiative forcings and global warming potentials of NF<sub>3</sub> and CF<sub>3</sub>CF<sub>2</sub>Cl (CFC-115)

2016 ◽  
Vol 16 (17) ◽  
pp. 11451-11463 ◽  
Author(s):  
Anna Totterdill ◽  
Tamás Kovács ◽  
Wuhu Feng ◽  
Sandip Dhomse ◽  
Christopher J. Smith ◽  
...  
Keyword(s):  
Global Warming ◽  
Cross Sections ◽  
Infrared Absorption ◽  
Radiative Forcing ◽  
Climate Model ◽  
Intergovernmental Panel ◽  
Radiative Forcings ◽  
Radiative Efficiency ◽  
Atmospheric Window ◽  
Global Warming Potentials

Abstract. Fluorinated compounds such as NF3 and C2F5Cl (CFC-115) are characterised by very large global warming potentials (GWPs), which result from extremely long atmospheric lifetimes and strong infrared absorptions in the atmospheric window. In this study we have experimentally determined the infrared absorption cross sections of NF3 and CFC-115, calculated the radiative forcing and efficiency using two radiative transfer models and identified the effect of clouds and stratospheric adjustment. The infrared cross sections are within 10 % of previous measurements for CFC-115 but are found to be somewhat larger than previous estimates for NF3, leading to a radiative efficiency for NF3 that is 25 % larger than that quoted in the Intergovernmental Panel on Climate Change Fifth Assessment Report. A whole atmosphere chemistry–climate model was used to determine the atmospheric lifetimes of NF3 and CFC-115 to be (509 ± 21) years and (492 ± 22) years, respectively. The GWPs for NF3 are estimated to be 15 600, 19 700 and 19 700 over 20, 100 and 500 years, respectively. Similarly, the GWPs for CFC-115 are 6030, 7570 and 7480 over 20, 100 and 500 years, respectively.

The Status Nomenclature of the Imperial Freedmen

1963 ◽  
Vol 13 (2) ◽  
pp. 272-278 ◽  
Author(s):  
P. R. C. Weaver
Keyword(s):  
Social Status ◽  
Recent Article ◽  
The Other ◽  
Contributory Factor ◽  
Imperial Rome ◽  
Other Hand ◽  
The Status ◽  
Inferior Status

Lily Ross Taylor in an interesting recent article on the proportion of freedmen to freeborn in the sepulchral inscriptions of Imperial Rome discusses the increasing omission of status nomenclature by freedmen in the first and second centuries A.D. and the consequent difficulty of determining the status of persons whose names appear in the epitaphs. One contributory factor to this decline in the traditional nomenclature which she mentions is the growing numbers and importance of the freedmen of the emperor, the Augusti liberti. While non-imperial freedmen were anxious to record their acquisition of citizenship, but not their inferior status in the citizen body, the emperor's freedmen, on the other hand, increasingly formalized their status nomenclature so that the formula ‘Aug. lib.’ proclaimed not only the fact of their manumission within the Familia Caesaris but also the higher social status which they enjoyed. An examination of the nomenclature of the Imperial freedmen might help to throw some light on this process, particularly on the problem of dating.

On the structure of instantaneous radiative forcing kernels for greenhouse gases

2020 ◽  
Author(s):  
Amanda C. Maycock ◽  
Christopher J. Smith ◽  
Alexandru Rap ◽  
Owain Rutherford
Keyword(s):  
Greenhouse Gases ◽  
Water Vapour ◽  
Radiative Forcing ◽  
Small Amplitude ◽  
The Other ◽  
Background Concentration ◽  
Upper Troposphere ◽  
Water Vapour Absorption ◽  
Cloud Radiative Effects ◽  
Absorption Features

AbstractThe SOCRATES offline radiative transfer code is used to investigate the magnitude and structure of the instantaneous radiative forcing kernels (IRFKs) for five major greenhouse gases (GHGs; CO2, CH4, N2O, CFC-11, and O3). All gases produce IRFKs that peak in the tropical upper troposphere. In addition to differences in spectroscopic intensities and the position of absorption features relative to the peak of the Planck function for Earth’s temperature, the variation in current background concentration of gases substantially affects the IRFK magnitudes. When the background concentration of CO2 is reduced from parts per million to parts per trillion levels, the peak magnitude of the IRFK increases by a factor of 642. When all gases are set to parts per trillion concentrations in the troposphere, the peak IRFK magnitudes are 1.0, 3.0, 3.1, 58 and 75 Wm−2 ppmv−1 100 hPa−1 for CH4, CO2, N2O, O3 and CFC-11, respectively. The altitude of the IRFK maximum also differs, with the maximum for CFC-11 and water vapour occurring above 100 hPa while the other gases peak near 150-200 hPa. Overlap with water vapour absorption decreases the magnitude of the IRFKs for all the GHGs, particularly in the low-to-mid troposphere, but it does not strongly affect the peak IRFK altitude. Cloud radiative effects reduce the magnitude of the IRFK for CO2 by around 10-20% in the upper troposphere. The use of IRFKs to estimate IRF is found to be accurate for small amplitude perturbations, but becomes inaccurate for large amplitude changes (e.g. a doubling) for gases with a higher atmospheric optical depth.

scholarly journals Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

2014 ◽  
Vol 14 (15) ◽  
pp. 8089-8103 ◽  
Author(s):  
S. Kaspari ◽  
T. H. Painter ◽  
M. Gysel ◽  
S. M. Skiles ◽  
M. Schwikowski
Keyword(s):  
Water Resources ◽  
Radiative Transfer ◽  
Radiative Forcing ◽  
The Other ◽  
Radiative Forcings ◽  
Ice Melt ◽  
Radiative Transfer Modeling ◽  
The Himalaya ◽  
Snow And Ice Melt ◽  
Snow And Ice

Abstract. Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, providing the first observational data of BC concentrations in snow and ice from the southern slope of the Himalaya. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage and loss of BC particles in the ultrasonic nebulizer; thus, we correct for the underestimated BC mass. BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter–spring snow/ice horizons are sufficient to reduce albedo by 6–10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75–120 W m−2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40–42% relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m−2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m−2. The BC and Fe concentrations were used to further examine relative absorption of BC and dust. When dust concentrations are high, dust dominates absorption, snow albedo reduction, and radiative forcing, and the impact of BC may be negligible, confirming the radiative transfer modeling. When impurity concentrations are low, the absorption by BC and dust may be comparable; however, due to the low impurity concentrations, albedo reductions are small. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty. Further observational studies are needed to address the contribution of BC, dust, and colored organics to albedo reductions and snow and ice melt, and to characterize the time variation of radiative forcing.

“Palatal” and “palatalized” redefined

1966 ◽  
Vol 11 (2) ◽  
pp. 109-113 ◽  
Author(s):  
R. C. De Armond
Keyword(s):  
Recent Article ◽  
The Other ◽  
Slavic Languages ◽  
The Status

The purpose of this paper is to show that the term “palatal” has been used with various meanings and to redefine or establish a consistency of terminology concerning this term with respect to palatalized and central consonants. Confusion arising from the various divisions of the tongue into articulators and from the misuse of the above articulatory terms has led to incorrect phonological solutions.The status of Russian palatalized and palatal consonants has been under discussion recently. Dunatov claims in a recent article that Russian palatal consonants cannot be palatalized and suggests three different orders of palatals to distinguish “the three articulatory sets of palatals encountered in the Slavic languages”: pre-palatal, medio-palatal, and post-palatal. However, he fails to state the distribution of them in Russian or the other Slavic languages.

scholarly journals Northern Hemisphere contrail properties derived from Terra and Aqua MODIS data for 2006 and 2012

2019 ◽  
Vol 19 (8) ◽  
pp. 5313-5330 ◽  
Author(s):  
David P. Duda ◽  
Sarah T. Bedka ◽  
Patrick Minnis ◽  
Douglas Spangenberg ◽  
Konstantin Khlopenkov ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Detection Algorithm ◽  
Air Traffic ◽  
Effective Diameter ◽  
Radiative Forcings ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. Linear contrail coverage, optical property, and radiative forcing data over the Northern Hemisphere (NH) are derived from a year (2012) of Terra and Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) imagery and compared with previously published 2006 results (Duda et al., 2013; Bedka et al., 2013; Spangenberg et al., 2013) using a consistent retrieval methodology. Differences in the observed Terra-minus-Aqua screened contrail coverage and patterns in the 2012 annual-mean air traffic estimated with respect to satellite overpass time suggest that most contrails detected by the contrail detection algorithm (CDA) form approximately 2 h before overpass time. The 2012 screened NH contrail coverage (Mask B) shows a relative 3 % increase compared to 2006 data for Terra and increases by almost 7 % for Aqua, although the differences are not expected to be statistically significant. A new post-processing algorithm added to the contrail mask processing estimated that the total contrail cirrus coverage visible in the MODIS imagery may be 3 to 4 times larger than the linear contrail coverage detected by the CDA. This estimate is similar in magnitude to the spreading factor estimated by Minnis et al. (2013). Contrail property retrievals of the 2012 data indicate that both contrail optical depth and contrail effective diameter decreased approximately 10 % between 2006 and 2012. The decreases may be attributed to better background cloudiness characterization, changes in the waypoint screening, or changes in contrail temperature. The total mean contrail radiative forcings (TCRFs) for all 2012 Terra observations were −6.3, 14.3, and 8.0 mW m−2 for the shortwave (SWCRF), longwave (LWCRF), and net forcings, respectively. These values are approximately 20 % less than the corresponding 2006 Terra estimates. The decline in TCRF results from the decrease in normalized CRF, partially offset by the 3 % increase in overall contrail coverage in 2012. The TCRFs for 2012 Aqua are similar, −6.4, 15.5, and 9.0 mW m−2 for shortwave, longwave, and net radiative forcing. The strong correlation between the relative changes in both total SWCRF and LWCRF between 2006 and 2012 and the corresponding relative changes in screened contrail coverage over each air traffic region suggests that regional changes in TCRF from year to year are dominated by year-to-year changes in contrail coverage over each area.

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