scholarly journals Determination of the atmospheric lifetime and global warming potential of sulphur hexafluoride using a three-dimensional model

2016 ◽  
Author(s):  
Tamás Kovács ◽  
Wuhu Feng ◽  
Anna Totterdill ◽  
John M. C. Plane ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Global Warming ◽  
Electron Density ◽  
Climate Model ◽  
Three Dimensional ◽  
Negative Ions ◽  
Cluster Ions ◽  
Ion Chemistry ◽  
Three Dimensional Model ◽  
Atmospheric Lifetime ◽  
Metal Atoms

Abstract. We have used the Whole Atmosphere Community Climate Model (WACCM), with an updated treatment of loss processes, to determine the atmospheric lifetime of SF6. The model includes the following SF6 removal processes: photolysis, electron attachment and reaction with mesospheric metal atoms. The Sodankylä Ion Chemistry (SIC) model is incorporated into the standard version of WACCM to produce a new version with a detailed D region ion chemistry with cluster ions and negative ions. This is used to determine a latitude- and altitude-dependent scaling factor for the electron density in the standard WACCM in order to carry out multi-year SF6 simulations. The model gives a mean SF6 lifetime over a 11-year solar cycle (τ) of 1278 years (with a range from 1120 to 1475 years), which is much shorter than the currently widely used value of 3200 years, due to the larger contribution (97.4 %) of the modelled electron density to the total atmospheric loss. The loss of SF6 by reaction with mesospheric metal atoms (Na and K) is far too slow to affect the lifetime. We investigate how this shorter atmospheric lifetime impacts the use of SF6 to derive stratospheric age-of-air. The age-of-air derived from this shorter lifetime SF6 tracer is longer by 9 % in polar latitudes at 20 km compared to a passive SF6 tracer. We also present laboratory measurements of the infrared spectrum of SF6 and find good agreement with previous studies. We calculate the resulting radiative forcings and efficiencies to be, on average, very similar to those reported previously. Our values for the 20, 100 and 500-year global warming potentials are 18,000, 23,800 and 31,300, respectively.

scholarly journals Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model

2017 ◽  
Vol 17 (2) ◽  
pp. 883-898 ◽  
Author(s):  
Tamás Kovács ◽  
Wuhu Feng ◽  
Anna Totterdill ◽  
John M. C. Plane ◽  
Sandip Dhomse ◽  
...  
Keyword(s):  
Global Warming ◽  
Electron Density ◽  
Sulfur Hexafluoride ◽  
Climate Model ◽  
Negative Ions ◽  
Cluster Ions ◽  
Ion Chemistry ◽  
Three Dimensional Model ◽  
Atmospheric Lifetime ◽  
Metal Atoms

Abstract. We have used the Whole Atmosphere Community Climate Model (WACCM), with an updated treatment of loss processes, to determine the atmospheric lifetime of sulfur hexafluoride (SF6). The model includes the following SF6 removal processes: photolysis, electron attachment and reaction with mesospheric metal atoms. The Sodankylä Ion Chemistry (SIC) model is incorporated into the standard version of WACCM to produce a new version with a detailed D region ion chemistry with cluster ions and negative ions. This is used to determine a latitude- and altitude-dependent scaling factor for the electron density in the standard WACCM in order to carry out multi-year SF6 simulations. The model gives a mean SF6 lifetime over an 11-year solar cycle (τ) of 1278 years (with a range from 1120 to 1475 years), which is much shorter than the currently widely used value of 3200 years, due to the larger contribution (97.4 %) of the modelled electron density to the total atmospheric loss. The loss of SF6 by reaction with mesospheric metal atoms (Na and K) is far too slow to affect the lifetime. We investigate how this shorter atmospheric lifetime impacts the use of SF6 to derive stratospheric age of air. The age of air derived from this shorter lifetime SF6 tracer is longer by 9 % in polar latitudes at 20 km compared to a passive SF6 tracer. We also present laboratory measurements of the infrared spectrum of SF6 and find good agreement with previous studies. We calculate the resulting radiative forcings and efficiencies to be, on average, very similar to those reported previously. Our values for the 20-, 100- and 500-year global warming potentials are 18 000, 23 800 and 31 300, respectively.

Interactive visualization of electron density slices

2005 ◽  
Vol 38 (3) ◽  
pp. 563-565 ◽  
Author(s):  
Filipe R. N. C. Maia ◽  
Abraham Szöke ◽  
Warren DeLano ◽  
David van der Spoel
Keyword(s):  
High Resolution ◽  
Quantum Chemistry ◽  
Electron Density ◽  
Three Dimensional ◽  
Structure Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Molecular Visualization ◽  
Density Maps ◽  
Quantum Chemistry Calculations

A new tool has been developed to aid in the visualization of electron density in crystals or from quantum chemistry calculations. It displays the fine details of the electron density on a plane and the three-dimensional model of the molecule at the same time. The program enables the user to examine the details of weak or irregular features. Such features frequently occur in low-resolution maps, where they determine the correct tracing of a protein backbone. In high-resolution maps, solvent regions are difficult or impossible to observe using isosurfaces. The tool has been integrated into an existing molecular visualization package (PyMol) making it possible to observe and interact both with a structure model and the electron density slices freely, simultaneously and independently. This visualization model fills a gap in the visualization methods available to crystallographers and others who work with electron density maps.

scholarly journals <i>D</i>-region ion–neutral coupled chemistry (Sodankylä Ion Chemistry, SIC) within the Whole Atmosphere Community Climate Model (WACCM 4) – WACCM-SIC and WACCM-rSIC

2016 ◽  
Vol 9 (9) ◽  
pp. 3123-3136 ◽  
Author(s):  
Tamás Kovács ◽  
John M. C. Plane ◽  
Wuhu Feng ◽  
Tibor Nagy ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Climate Model ◽  
Negative Ions ◽  
Solar Proton ◽  
Proton Event ◽  
Ion Chemistry ◽  
Neutral Species ◽  
Community Climate Model ◽  
Ion Molecule Reactions ◽  
D Region ◽  
Community Climate

Abstract. This study presents a new ion–neutral chemical model coupled into the Whole Atmosphere Community Climate Model (WACCM). The ionospheric D-region (altitudes ∼  50–90 km) chemistry is based on the Sodankylä Ion Chemistry (SIC) model, a one-dimensional model containing 307 ion–neutral and ion recombination, 16 photodissociation and 7 photoionization reactions of neutral species, positive and negative ions, and electrons. The SIC mechanism was reduced using the simulation error minimization connectivity method (SEM-CM) to produce a reaction scheme of 181 ion–molecule reactions of 181 ion–molecule reactions of 27 positive and 18 negative ions. This scheme describes the concentration profiles at altitudes between 20 km and 120 km of a set of major neutral species (HNO3, O3, H2O2, NO, NO2, HO2, OH, N2O5) and ions (O2+, O4+, NO+, NO+(H2O), O2+(H2O), H+(H2O), H+(H2O)2, H+(H2O)3, H+(H2O)4, O3−, NO2−, O−, O2, OH−, O2−(H2O), O2−(H2O)2, O4−, CO3−, CO3−(H2O), CO4−, HCO3−, NO2−, NO3−, NO3−(H2O), NO3−(H2O)2, NO3−(HNO3), NO3−(HNO3)2, Cl−, ClO−), which agree with the full SIC mechanism within a 5 % tolerance. Four 3-D model simulations were then performed, using the impact of the January 2005 solar proton event (SPE) on D-region HOx and NOx chemistry as a test case of four different model versions: the standard WACCM (no negative ions and a very limited set of positive ions); WACCM-SIC (standard WACCM with the full SIC chemistry of positive and negative ions); WACCM-D (standard WACCM with a heuristic reduction of the SIC chemistry, recently used to examine HNO3 formation following an SPE); and WACCM-rSIC (standard WACCM with a reduction of SIC chemistry using the SEM-CM method). The standard WACCM misses the HNO3 enhancement during the SPE, while the full and reduced model versions predict significant NOx, HOx and HNO3 enhancements in the mesosphere during solar proton events. The SEM-CM reduction also identifies the important ion–molecule reactions that affect the partitioning of odd nitrogen (NOx), odd hydrogen (HOx) and O3 in the stratosphere and mesosphere.

Negative chlorine ion chemistry in the upper stratosphere and its application to an artificially created dense electron cloud

1995 ◽  
Vol 13 (3) ◽  
pp. 296-304 ◽  
Author(s):  
S. S. Prasad
Keyword(s):  
Major Ions ◽  
Negative Ions ◽  
Electron Cloud ◽  
Negative Ion ◽  
Cluster Ions ◽  
Aerosol Formation ◽  
Ion Chemistry ◽  
Catalytic Destruction ◽  
Three Body ◽  
Chlorine Ion

Abstract. This paper discusses new potential reactions of chlorine-bearing anions (negative ions) in the upper stratosphere. These reactions are then applied to the negative-ion chemistry following the injection of an electron cloud of very high density, of the order of 106-107 e- cm-3, in the 40-45-km region. The idea is to evaluate the recently proposed scheme to mitigate ozone depletion by converting the reactive chlorine atoms at these altitudes into Cl- ions which are unreactive towards ozone, i.e., electron scavenging of Cl. We find that the previously neglected photodetachment from Cl- is fast. For an overhead sun, this process may have a rate coefficient of 0.08 s-1 when multiple scattering is included. The rate could be even higher, depending on the ground albedo. Switching reaction between Cl-·H2O and HCl might lead to the formation of Cl-·HCl anion. Possible reactions of Cl-·H2O and Cl-·HCl with O atoms could produce ClO- and Cl-2. The production of ClO- in this manner is significant because Cl- having a high photodetachment rate constant would be regenerated in the very likely reactions of ClO- with O. When these possibilities are considered, then it is found that the chlorine anions may not be the major ions inside the electron cloud due to the rapid photodetachment from Cl-. Furthermore, in such a cloud, there may be the hazard that the Cl--Cl-·H2O-ClO--Cl- cycle amounts to catalytic destruction of two O atoms. Thus, the scheme could be risky if practised in the altitude region where atomic oxygen is an important constituent. Similar conclusions apply even if the ClO- species forms ClO-3 by three-body association with O2, instead of reacting with O. It must be emphasized that the present study is speculative at this time, because none of the relevant reactions have been investigated in the laboratory as yet. Nevertheless, it is very safe to say that the scheme of ozone preservation by electron scavenging of the upper stratospheric Cl is much less certain than implied in the studies reported by its original proponents, because those studies neglected the photodetachment from Cl- and made the highly unlikely assumption that the Cl-·H2O anion neither photodissociates nor reacts any further. The situation at the lower altitudes could be even more complex due to the formation of large cluster ions and the ion-induced aerosol formation. The lower atmospheric situation, therefore, requires much more study. The uncertainties in the scavenging scheme due to the electrostatic repulsion in the cloud should also be addressed. Despite the uncertainties about its environmental engineering usefulness, the emerging technology for artificial creation of plasmas, with any desired density and charge in the stratosphere, could have significant pure scientific values in the studies of stratospheric ion chemistry and ion-induced aerosol formation. Such studies have perennially suffered from the extremely low densities of the naturally occurring plasma.

scholarly journals Atmospheric lifetimes and Ozone Depletion Potentials of trans-1-chloro-3,3,3-trifluoropropylene and trans-1,2-dichloroethylene in a three-dimensional model

2010 ◽  
Vol 10 (22) ◽  
pp. 10867-10874 ◽  
Author(s):  
K. O. Patten ◽  
D. J. Wuebbles
Keyword(s):  
Environmental Effects ◽  
Atmospheric Chemistry ◽  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Atmospheric Lifetime ◽  
Ozone Loss ◽  
Land Surfaces

Abstract. The chloroalkenes trans-1-chloro-3,3,3-trifluoropropylene (tCFP) and trans-1,2-dichloroethylene (tDCE) have been proposed as candidate replacements for other compounds in current use that cause concerns regarding potential environmental effects including destruction of stratospheric ozone. Because tCFP and tDCE contain chlorine atoms, the effects of these short-lived compounds on stratospheric ozone must be established. In this study, we derive the atmospheric lifetimes and Ozone Depletion Potentials (ODPs) for tCFP and for tDCE assuming emissions from land surfaces at latitudes 30° N to 60° N using the MOZART 3 three-dimensional model of atmospheric chemistry and physics. 53% of the ozone loss due to tCFP and 98% of the ozone loss due to tDCE take place in the troposphere, rather than in the stratosphere as generally expected from longer-lived chlorocarbons. The atmospheric lifetime of tCFP against chemical reaction is 40.4 days, and its ODP is quite small at 0.00034. The tDCE atmospheric lifetime is 12.7 days, and its ODP is 0.00024, which is the lowest ODP found for any chlorocarbon we have studied. Our study suggests that chlorine from tCFP and tDCE are unlikely to affect ozone at quantities likely to be emitted to the atmosphere.

scholarly journals Three-dimensional model evaluation of the Ozone Depletion Potentials for n-propyl bromide, trichloroethylene and perchloroethylene

2010 ◽  
Vol 10 (7) ◽  
pp. 17889-17910 ◽  
Author(s):  
D. J. Wuebbles ◽  
K. O. Patten ◽  
D. Wang ◽  
D. Youn ◽  
M. Martínez-Avilés ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Chemistry Transport Model ◽  
Atmospheric Lifetime ◽  
Land Surfaces ◽  
Simplified Modeling ◽  
First Time

Abstract. The existing solvents trichloroethylene (TCE) and perchloroethylene (PCE) and proposed solvent n-propyl bromide (nPB) have atmospheric lifetimes from days to a few months, but contain chlorine or bromine that could affect stratospheric ozone. Several previous studies estimated the Ozone Depletion Potentials (ODPs) for various assumptions for location of nPB emissions, but these studies used simplified modeling treatments. The primary purpose of this study is to reevaluate the ODP for nPB using a current-generation chemistry-transport model of the troposphere and stratosphere. For the first time, ODPs for TCE and PCE are also evaluated. Emissions representing industrial use of each compound are incorporated on land surfaces from 30° N to 60° N. The atmospheric chemical lifetime obtained for nPB is 24.7 days, similar to past literature, but the ODP is 0.0049, lower than in past studies. The derived atmospheric lifetime for TCE is 13.0 days and for PCE is 111 days. The corresponding ODPs are 0.00035 and 0.0060, respectively.

scholarly journals Photoelectron Spectroscopy of Mass-Selected Copper-Water Cluster Negative Ions

1995 ◽  
Vol 15 (2-4) ◽  
pp. 195-207 ◽  
Author(s):  
Fuminori Misaizu ◽  
Keizo Tsukamato ◽  
Masaomi Sanekata ◽  
Kiyokazu Fuke
Keyword(s):  
Photoelectron Spectroscopy ◽  
Negative Ions ◽  
Photoelectron Spectra ◽  
Negative Ion ◽  
Cluster Ions ◽  
Electron Detachment ◽  
Energy Bands ◽  
Size Dependent ◽  
Spectral Shifts ◽  
Metal Atoms

Negative-ion photoelectron spectroscopy has been applied in order to obtain size dependent information about the electronic structure of clusters of metal atoms solvated with polar molecules. In the present paper we have investigated the photoelectron spectra of Cu2-(H2O)n, cluster ions with 2 = 0–4 and also those of Cu2-(H2O)n, with n = 0 and 1. In the spectra of Cu2-(H2O)n, the lowest energy bands were assigned to the electron detachment from the CuOH-(H2O)n−1, which were produced in the source together with the above cluster ions. The observed bands for Cu2-(H2O)n were all assigned to the transitions to the states originating in the ground 2S and first excited 2D states of the Cu atom. The stepwise hydration for Cu- and Cu2- was discussed from the observed spectral shifts.

scholarly journals High-speed solar wind streams and polar mesosphere winter echoes at Troll, Antarctica

2015 ◽  
Vol 33 (6) ◽  
pp. 609-622 ◽  
Author(s):  
S. Kirkwood ◽  
A. Osepian ◽  
E. Belova ◽  
Y.-S. Lee
Keyword(s):  
Solar Wind ◽  
Electron Density ◽  
High Speed ◽  
Negative Ions ◽  
Solar Proton ◽  
Ion Chemistry ◽  
Molecular Ion ◽  
Speed Solar Wind ◽  
Solar Proton Events ◽  
High Speed Solar Wind

Abstract. A small, 54 MHz wind-profiler radar, MARA, was operated at Troll, Antarctica (72° S, 2.5° E), continuously from November 2011 to January 2014, covering two complete Antarctic winters. Despite very low power, MARA observed echoes from heights of 55–80 km (polar mesosphere winter echoes, PMWE) on 60% of all winter days (from March to October). This contrasts with previous reports from radars at high northern latitudes, where PWME have been reported only by very high power radars or during rare periods of unusually high electron density at PMWE heights, such as during solar proton events. Analysis shows that PWME at Troll were not related to solar proton events but were often closely related to the arrival of high-speed solar wind streams (HSS) at the Earth, with PWME appearing at heights as low as 56 km and persisting for up to 15 days following HSS arrival. This demonstrates that HSS effects penetrate directly to below 60 km height in the polar atmosphere. Using local observations of cosmic-noise absorption (CNA), a theoretical ionization/ion-chemistry model and a statistical model of precipitating energetic electrons associated with HSS, the electron density conditions during the HSS events are estimated. We find that PMWE detectability cannot be explained by these variations in electron density and molecular-ion chemistry alone. PWME become detectable at different thresholds depending on solar illumination and height. In darkness, PWME are detected only when the modelled electron density is above a threshold of about 1000 cm−3, and only above 75 km height, where negative ions are few. In daylight, the electron density threshold falls by at least 2 orders of magnitude and PWME are found primarily below 75 km height, even in conditions when a large proportion of negative ions is expected. There is also a strong dawn–dusk asymmetry with PWME detected very rarely during morning twilight but often during evening twilight. This behaviour cannot be explained if PMWE are caused by small-scale structure in the neutral/molecular-ion gas alone but may be explained by the presence of charged meteoric dust.

scholarly journals Negative ions in the auroral mesosphere during a PCA event around sunset

1999 ◽  
Vol 17 (6) ◽  
pp. 782-793 ◽  
Author(s):  
C. F. del Pozo ◽  
E. Turunen ◽  
T. Ulich
Keyword(s):  
Electron Density ◽  
Negative Ions ◽  
Spectral Width ◽  
High Energy ◽  
Negative Ion ◽  
Ion Temperature ◽  
Ion Chemistry ◽  
Ion Chemistry And Composition ◽  
Proton Precipitation ◽  
Precipitation Events

Abstract. This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation).

scholarly journals The influence of ozone concentration on the lower ionosphere – modelling and measurements during the 29–30 October 2003 solar proton event

2009 ◽  
Vol 27 (2) ◽  
pp. 577-589 ◽  
Author(s):  
A. Osepian ◽  
S. Kirkwood ◽  
P. Dalin
Keyword(s):  
Electron Density ◽  
Ozone Concentration ◽  
Negative Ions ◽  
Solar Proton ◽  
Proton Event ◽  
Ion Chemistry ◽  
Density Profiles ◽  
Proton Fluxes ◽  
D Region ◽  
Electron Density Profiles

Abstract. A numerical model of D-region ion chemistry is used to study the influence of the ozone concentration in the mesosphere on ion-composition and electron density during solar proton events (SPE). We find a strong sensitivity in the lower part of the D-region, where negative ions play a major role in the ionization balance. We have chosen the strong SPE on 29–30 October 2003 when very intense proton fluxes with a hard energetic spectrum were observed. Deep penetration into the atmosphere by the proton fluxes and strong ionisation allows us to use measurements of electron density, made by the EISCAT 224 MHz radar, starting from as low as 55 km. We compare the electron density profiles with model results to determine which ozone concentration profiles are the most appropriate for mesospheric altitudes under SPE conditions. We show that, during daytime, an ozone profile corresponding to depletion by a factor of 2 compared to minimum model concentrations for quiet conditions (Rodrigo et al., 1986), is needed to give model electron density profiles consistent with observations. Simple incorporation of minor neutral constituent profiles (NO, O and O3) appropriate for SPE conditions into ion-chemistry models will allow more accurate modeling of electron and ion densities during such events, without the need to apply a complete chemical model calculating all neutral species.

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