Sulfur dioxide in remote oceanic air: Cloud transport of reactive precursors
TL;DR: In this article, the authors present simulations with a two-dimensional "Staubsauger" or "vacuum cleaner" model that combines a photochemical model with a description of vertical transport of trace species by convective clouds within larger synoptic circulations.
Abstract: Reactive surface emissions of reduced sulfur gases can produce SO2 in the middle and upper troposphere at the levels of 80±30 pptv measured high over the remote oceans. We present simulations with a two-dimensional “Staubsauger” or “vacuum cleaner” model that combines a photochemical model with a description of vertical transport of trace species by convective clouds within larger synoptic circulations. Emissions of 20–60 Tg (S)/yr of (CH3)2S, H2S, or CS2, may produce the observed SO2. Roughly equal production rates of SO2 and methane sulfonic acid may be expected. The amount and exact vertical distribution of the SO2 produced remain uncertain: the greatest chemical uncertainties are the reaction yield of SO2 expectable under clean tropospheric conditions and also the liquid-phase removal of SO2, and the oxidation rate. The amount of upper tropospheric SO2 produced depends substantially on the proximity of strong reduced S sources to regions of active convection. However, the character of the solutions we present is invariably distinctly different from those obtained with one- or two-dimensional models employing the eddy-diffusion hypothesis. The results of the model point beyond its original conception, and stress the likely importance of the rainy tropical jungles and mid-latitude industrial regions, since both regions have large sulfur emissions arid frequently active cumulonimbus convection. This process, however, should contribute mainly to upper-tropospheric SO2. Other chemical implications are that tropospheric OH may depend critically on HOOH levels as well as the hydrocarbon and nitrogen oxide cycles. Cloud transport may play an important role in these cycles. The hydroxyl radical concentration depends as much on assumptions regarding HOOH reaction and transport as it does on NO levels.
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TL;DR: In this paper, it was shown that photodissociation rate coefficients inside clouds, and particularly inside cloud droplets, can frequently exceed the clear-sky values, in contrast to current usage in cloud chemistry models, due to the ∼2 cos θ factor incurred in the actinic flux when the solar beam is scattered and diffused into nearly isotropic light.
Abstract: The actinic flux must be distinguished from other radiometric quantities such as the irradiance. This distinction shows that (1) a fraction of the recent atmospheric chemistry literature contains improperly calculated rates of photodissociation, and (2) photodissociation rate coefficients inside clouds, and particularly inside cloud droplets, can frequently exceed the clear-sky values, in contrast to current usage in cloud chemistry models. Both of these findings are traceable to the ∼2 cos θ factor incurred in the actinic flux (but not in the irradiance) when the solar beam is scattered and diffused into nearly isotropic light.
764 citations
TL;DR: Models and the observational network for oxidants are improving, but validation of global models is still at an early stage and positive and negative trends possible for OH and H2O2.
Abstract: A number of critical atmospheric chemical problems depend on the earth's oxidizing capacity, which is essentially the global burden of oxidants in the lower atmosphere. There is limited direct evidence for changes in the earth's oxidizing capacity since recent preindustrial times when, because of industrial and poulation growth, increasing amounts of O3 precursor trace gases (carbon monoxide, nitrogen oxides, and hydrocarbons) have been released into the atmosphere. The concentrations of O3 and possibly H2O2 have increased over large regions. Models predict that tropospheric O3 will increase about 0.3-1.0 percent per year over the next 50 years with both positive and negative trends possible for OH and H2O2. Models and the observational network for oxidants are improving, but validation of global models is still at an early stage.
764 citations
TL;DR: The ability of these aerosol particles to nucleate cloud droplets, and thereby influence the reflectivity and stability of clouds, forms the basis of a proposed geophysiological feedback loop involving phytoplankton, atmospheric sulfur, and climate as discussed by the authors.
655 citations
TL;DR: The best estimate of the annual global LNOx nitrogen oxides nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this paper, implying larger flash-specific NOx emissions.
Abstract: . The knowledge of the lightning-induced nitrogen oxides (LNOx) source is important for understanding and predicting the nitrogen oxides and ozone distributions in the troposphere and their trends, the oxidising capacity of the atmosphere, and the lifetime of trace gases destroyed by reactions with OH. This knowledge is further required for the assessment of other important NOx sources, in particular from aviation emissions, the stratosphere, and from surface sources, and for understanding the possible feedback between climate changes and lightning. This paper reviews more than 3 decades of research. The review includes laboratory studies as well as surface, airborne and satellite-based observations of lightning and of NOx and related species in the atmosphere. Relevant data available from measurements in regions with strong LNOx influence are identified, including recent observations at midlatitudes and over tropical continents where most lightning occurs. Various methods to model LNOx at cloud scales or globally are described. Previous estimates are re-evaluated using the global annual mean flash frequency of 44±5 s−1 reported from OTD satellite data. From the review, mainly of airborne measurements near thunderstorms and cloud-resolving models, we conclude that a "typical" thunderstorm flash produces 15 (2–40)×1025 NO molecules per flash, equivalent to 250 mol NOx or 3.5 kg of N mass per flash with uncertainty factor from 0.13 to 2.7. Mainly as a result of global model studies for various LNOx parameterisations tested with related observations, the best estimate of the annual global LNOx nitrogen mass source and its uncertainty range is (5±3) Tg a−1 in this study. In spite of a smaller global flash rate, the best estimate is essentially the same as in some earlier reviews, implying larger flash-specific NOx emissions. The paper estimates the LNOx accuracy required for various applications and lays out strategies for improving estimates in the future. An accuracy of about 1 Tg a−1 or 20%, as necessary in particular for understanding tropical tropospheric chemistry, is still a challenging goal.
573 citations
Cites background from "Sulfur dioxide in remote oceanic ai..."
...Examples are CO (Logan et al., 1981), sulphur dioxide (SO2) (Chatfield and Crutzen, 1984), CH4 2627 ACPD 7, 2623–2818, 2007 The global lightning-induced nitrogen oxides source U. Schumann and H. Huntrieser Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back…...
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...Examples are CO (Logan et al., 1981), sulphur dioxide (SO2) (Chatfield and Crutzen, 1984), CH4 2627 ACPD 7, 2623–2818, 2007 The global lightning-induced nitrogen oxides source U. Schumann and H. Huntrieser Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU (Lelieveld et al., 1998; Bousquet et al., 2006), and further O3 and aerosol precursors or gases relevant to climate that get oxidised by reactions with OH....
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...Condensation nuclei have been observed both in the laboratory and the atmosphere to be formed by flashes possibly due to nucleation of nitric acid (Peyrous and Lapeyre, 1982) or from sulphuric acid produced by oxidation of SO2 with H2O2 in the aqueous10 phase (Chameides, 1986)....
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...…of humidity and HOx precursors like hydrogen peroxide (H2O2), methylhydroperoxide (CH3OOH), and formaldehyde (HCHO) transported upwards with the convective storm (Chatfield and Crutzen, 1984; Jaeglé et al., 1997; Prather and Jacob, 1997; Ko et al., 2003; DeCaria et al., 2005; Ott et al., 2007)....
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TL;DR: In this paper, the authors used an Eulerian transport model, the MOGUNTIA model, with a horizontal resolution of 10° longitude by 10° latitude and with 10 layers in the vertical between the surface and 100 hPa.
Abstract: The tropospheric part of the atmospheric sulfur cycle has been simulated in a global three-dimensional model. The model treats the emission, transport, chemistry, and removal processes for three sulfur components; DMS (dimethyl sulfide), SO2 and SO4
2− (sulfate). These processes are resolved using an Eulerian transport model, the MOGUNTIA model, with a horizontal resolution of 10° longitude by 10° latitude and with 10 layers in the vertical between the surface and 100 hPa. Advection takes place by climatological monthly mean winds. Transport processes occurring on smaller space and time scales are parameterized as eddy diffusion except for transport in deep convective clouds which is treated separately. The simulations are broadly consistent with observations of concentrations in air and precipitation in and over polluted regions in Europe and North America. Oxidation of DMS by OH radicals together with a global emission of 16 Tg DMS-S yr−1 from the oceans result in DMS concentrations consistent with observations in the marine boundary layer. The average turn-over times were estimated to be 3, 1.2–1.8, and 3.2–6.1 days for DMS, SO2, and SO4
2− respectively.
514 citations
Cites methods from "Sulfur dioxide in remote oceanic ai..."
...Chatfield and Crutzen (1984) used a two-dimensional model of the atmospheric circulation 226 J. LANGNER AND H. RODHE in tropical marine environments to demonstrate the importance of vertical transport in convective clouds for the distribution of sulfur compounds in the marine atmosphere and,…...
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01 Jan 1973TL;DR: CRC handbook of chemistry and physics, CRC Handbook of Chemistry and Physics, CRC handbook as discussed by the authors, CRC Handbook for Chemistry and Physiology, CRC Handbook for Physics,
Abstract: CRC handbook of chemistry and physics , CRC handbook of chemistry and physics , کتابخانه مرکزی دانشگاه علوم پزشکی تهران
52,268 citations
TL;DR: A critical evaluation of the kinetics and photochemistry of gas phase chemical reactions of neutral species involved in middle atmosphere chemistry (10-55 km altitude) was carried out by the authors under the auspices of the CODATA Task Group on Chemical Kinetics.
Abstract: This paper contains a critical evaluation of the kinetics and photochemistry of gas phase chemical reactions of neutral species involved in middle atmosphere chemistry (10–55 km altitude). The work has been carried out by the authors under the auspices of the CODATA Task Group on Chemical Kinetics. Data sheets have been prepared for 148 thermal and photochemical reactions, containing summaries of the available experimental data with notes giving details of the experimental procedures. For each reaction a preferred value of the rate coefficient at 298 K is given together with a temperature dependency where possible. The selection of the preferred value is discussed, and estimates of the accuracies of the rate coefficients and temperature coefficients have been made for each reaction. The data sheets are intended to provide the basic physical chemical data needed as input for calculations which model atmospheric chemistry. A table summarizing the preferred rate data is provided, together with an Appendix listing the available data on enthalpies of formation of the reactant and product species.
1,661 citations
TL;DR: The bulk properties of tropical cloud clusters, such as the vertical mass flux, the excess temperature, and moisture and the liquid water content of the clouds, are determined from a combination of the observed large-scale heat and moisture budgets over an area covering the cloud cluster, and a model of a cumulus ensemble which exchanges mass, heat, water vapor and liquid water with the environment through entrainment and detrainment.
Abstract: The bulk properties of tropical cloud clusters, such as the vertical mass flux, the excess temperature, and moisture and the liquid water content of the clouds, are determined from a combination of 1) the observed large-scale heat and moisture budgets over an area covering the cloud cluster, and 2) a model of a cumulus ensemble which exchanges mass, heat, water vapor and liquid water with the environment through entrainment and detrainment The method also provides an understanding of how the environmental air is heated and moistened by the cumulus convection An estimate of the average cloud cluster properties and the heat and moisture balance of the environment, obtained from 1956 Marshall Islands data, is presented
1,657 citations
TL;DR: In this paper, the use of a two-layer model to estimate the flux of various gases across the air-sea interface has been described, and the model has been used to estimate flux of different gases across different regions of the world.
Abstract: This article describes the use of a two-layer model to estimate the flux of various gases across the air-sea interface.
1,384 citations
TL;DR: In this paper, the authors described the rate constants for thermal unimolecular reactions and recombinations at the low pressure limit, at the high pressure limit and in the intermediate falloff range.
Abstract: This paper describes the calculation of rate constants for thermal unimolecular reactions and recombinations at the low pressure limit, at the high pressure limit, and in the intermediate falloff range, as well as the calculation of specific rate constants for unimolecular rearrangements. The most uncertain factors of the theory are identified by comparison with the NO/sub 2/, ClNO, H/sub 2/O, and O/sub 3/ systems. Weak collision and centrifugal barrier effects are discussed for low pressure rate constants. Simplified adiabatic channel calculations are proposed for specific rate constants and high pressure rate constants. Reduced falloff curves are presented in factorized form with weak collision and strong collision broadening factors. Simple falloff expressions are derived. 5 figures, 44 references, 3 tables.
764 citations