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1.
Following numerous model studies of the global impacts of sub- and supersonic aircraft on the atmosphere, this paper assesses the separate aircraft engine exhaust effects of the 45°N cruise flight and at the 10- and 18-km levels of the July atmosphere. A box diffusion photochemical model in the cross-section plane of the flight trajectory is used to compute the effects of gas-phase and heterogeneous reactions on the condensation trail particles in the troposphere, and on the sulphate aerosols in the stratosphere. The enhanced horizontal dispersion of the exhaust plume is considered in the model.A significant but short term depletion of ozone is predicted, which is 99% restored in about 1 h in the wide plume with enhanced horizontal dispersion, but requires more than 24 h in the narrow plume without it. The oxidation rate of NO and NO2 into the HNO3 depends on the OH content in the exhausts and varies in all the cases. The heterogeneous photochemistry has only a small influence on the initial evolution of N2O5 and HO2 in the plume.  相似文献   

2.
We evaluate the influence of the galactic cosmic rays (GCR), solar proton events (SPE), and energetic electron precipitation (EEP) on chemical composition of the atmosphere, dynamics, and climate using the chemistry-climate model SOCOL. We have carried out two 46-year long runs. The reference run is driven by a widely employed forcing set and, for the experiment run, we have included additional sources of NO x and HO x caused by all considered energetic particles. The results show that the effects of the GCR, SPE, and EEP fluxes on the chemical composition are most pronounced in the polar mesosphere and upper stratosphere; however, they are also detectable and statistically significant in the lower atmosphere consisting of an ozone increase up to 3?% in the troposphere and ozone depletion up to 8?% in the middle stratosphere. The thermal effect of the ozone depletion in the stratosphere propagates down, leading to a warming by up to 1?K averaged over 46?years over Europe during the winter season. Our results suggest that the energetic particles are able to affect atmospheric chemical composition, dynamics, and climate.  相似文献   

3.
The comprehensive chemistry module CHEM has been developed for application in general circulation models (GCMs) describing tropospheric and stratospheric chemistry, including photochemical reactions and heterogeneous reactions on sulphate aerosols and polar stratospheric clouds. It has been coupled to the spectral atmospheric GCM ECHAM3. The model configuration used in the current study has been run in an –off-line mode, i.e. the calculated chemical species do not affect the radiative forcing of the dynamic fields. First results of a 15-year model integration indicate that the model ECHAM3/CHEM runs are numerically efficient and stable, i.e. that no model drift can be detected in dynamic and chemical parameters. The model reproduces the main features regarding ozone, in particular intra- and interannual variability. The ozone columns are somewhat higher than observed (approximately 10%), while the amplitude of the annual cycle is in agreement with observations. A comparison with HALOE data reveals, however, a serious model deficiency regarding lower-stratosphere dynamics at high latitudes. Contrary to what is concluded by observations, the lower stratosphere is characterized by slight upward motions in the polar regions, so that some of the mentioned good agreements must be considered as fortuitous. Nevertheless, ECHAM3/CHEM well describes the chemical processes leading to ozone reduction. It has been shown that the mean fraction of the northern hemisphere, which is covered by polar stratospheric clouds (PSCs) as well as the temporal appearance of PSCs in the model, is in fair agreement with observations. The model results show an activation of chlorine inside the polar vortex which is stronger in the southern than in the northern winter hemisphere, yielding an ozone hole over the Antarctic; this hole, however, is also caused to a substantial degree by the dynamics. Interhemispheric differences concerning reformation of chlorine reservoir species HCl and ClONO2 in spring have also been well reproduced by the model.  相似文献   

4.
The ultraviolet Earth radiance data from the backscatter ultraviolet experiment on Nimbus 4 have been inverted to infer ozone profiles using a single Rayleigh scattering model. Two methods of solution give essentially the same results. Comparison of these profiles with simultaneous rocket sounding data shows satisfactory agreement at low and middle latitudes.Vertical cross-sections of ozone mixing ratio along the orbital tracks indicate that while the gross characteristics of the ozone field above 10 mb are under photochemical control, the influence of atmospheric motions can be found up to the 4 mb level.  相似文献   

5.
Accurate calculation of the solar radiation at the earth’s surface requires evaluation of the atmospheric ozone transmission. To use the existing methods one needs to know the atmospheric ozone amount. The serious lack of ozone data makes almost impossible the application of these methods in most of the world. In this paper a new method of estimating the overall ozone attenuation in the Northern Hemisphere is presented. Multiyear monthly latitudinal average ozone data are used. A daily ozone transmission function is proposed, and values of it are calculated for each latitudinal circle from 0° to 70°N at 10 longitude-degree intervals. By regression techniques parameterized expressions of the daily ozone transmission in the Northern Hemisphere are obtained as a function of the latitude. The model is applied to Athens, and the results are in excellent agreement with those obtained by extremely detailed calculations of the ozone transmission. The reliability of the model, under special regional ozone conditions, is investigated. Calculations for 67 locations in the Northern Hemisphere prove that the deviations do not exceed 1 percent. The influence of the year-by-year ozone variability is also examined, and the maximum deviation is found to be near 1.6 percent. The proposed model can be easily incoporated into solar radiation models in order to provide the ozone depletion at any place in the Northern Hemisphere where atmospheric ozone data are not available.  相似文献   

6.
The stratosphere holds a variety of particulates like polar stratospheric clouds (PSCs) and sulphate aerosols which catalyse chemical reactions. These reactions cause changes in the composition of the stratosphere, including the redistribution of active chlorine which might lead to ozone destruction. As a result during recent years a lot of effort has been directed towards the quantification of the uptake of trace gases like ClONO2, HCl, etc. into these particulates. However, it has been observed that many of the two and three dimensional models used in such studies are constrained by the lack of adequate rate constant data. This paper describes a theoretical approach to estimate the reaction rate constants for 23 gases on both types of polar stratospheric clouds (type I and II). It is found that for gases like N2O5, ClONO2 and HCl, diffusional uptake is important and contributes significantly to the heterogeneous reaction rate. A complete Lennard-Jones calculation is used to accurately compute the trace gas diffusion coefficients.  相似文献   

7.
During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions. Supported by National Natural Science Foundation of China (Grant Nos. 40775053 and 90711004), National Basic Research Program of China (Grant No. 2009CB421401), and Innovation Key Program of Chinese Academy of Sciences (Grant Nos. KZCXZ-YW-Q11-03, KZCZ2-YW-Q03-08)  相似文献   

8.
A discussion is given of atmospheric reactions in the H2O–CH4–O2–O3–NO x system. In the lower troposphere such reactions may lead to significant production of ozone. Their role in the odd hydrogen balance, especially of the troposphere and lower stratosphere, is discussed. CH3OH may be an intermediate in the oxidation cycle of methane, especially in the cold stratosphere. Its photodissociation into H2 and CH2O may consequently provide an important source for stratospheric H2. Catalytic photochemical chains of reactions involving NO x and HO x may also lead to tropospheric destruction of ozone. Due to lack of knowledge it is not possible at present to evaluate the importance of the before-mentioned reactions.With the aid of model calculations it is indicated that stratospheric ozone is most sensitive to changes in the adopted lower boundary values of N2O and that an increase in water vapour concentrations in the lower stratosphere will indeed cause some increase in ozone as predicted.Fluctuations in the flux of solar radiation near 190 nm may cause significant variations in stratospheric ozone concentrations.  相似文献   

9.
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10.
Long-term measurements of the ozone concentration in the vicinity of the city of Berlin have been performed with ground based Dobson spectrophotometers and balloon borne systems. The respective experiments cover the past 24 years. All data have been reevaluated and corrected towards uniform calibration standards, leading to the longest European data set of total column density, altitude-dependent ozone partial pressures and the corresponding temperatures. Smoothing algorithms unravel significant long-term trends.The analysis shows an increase of ozone concentration within the middle stratosphere (below 31 km height) as well as in the troposphere over the past 24 years. On the contrary, ongoing ozone depletion in the lower stratosphere has been found.The large scale vertical redistribution of atmospheric ozone in the troposphere and the lower stratosphere seems to be in agreement with model calculations and trend predictions that have their roots in changes of the chemical composition and the ozone photochemistry due to anthropogenically induced trace gas concentrations.Deutscher Wetterdienst, Meteorologisches Observatorium Potsdam.Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg.  相似文献   

11.
October 2003 solar proton events (SPE) is rather well covered by the observations; therefore its studies represent a good way for model validation and intercomparison. Here we apply chemistry–climate model (CCM) SOCOL with complete (SOCOLi) and parameterized ion chemistry to evaluate the accuracy of a commonly used ion chemistry parameterization scheme. We performed ensemble experiments with and without SPE to characterize the effect of the October 2003 SPE on the NOx, HOx, ClOx and O3 in the middle atmosphere. Preliminary comparison of the simulated effects against MIPAS observations revealed rather good general agreement for most of the species. Comparison of the results obtained with complete and parameterized ion chemistry representation showed that the model with parameterized ion chemistry underestimates the effect of SPE on chemical composition of the middle atmosphere by up to 40% for NOx and N2O, up to 70% for HOx and ClOx and up to 600% for HNO3. The parameterization is more accurate for ozone, however the model with parameterized ion chemistry underestimates ozone depletion by up to 15% during the SPE in the mesosphere and by 10% 2 weeks later in the stratosphere, which can be important for the long-term effects of SPE on the ozone layer.  相似文献   

12.
The catalytic destruction of stratospheric ozone by the oxides of nitrogen is believed to be an important part of the global ozone balance. The lack of sufficient measurements of NO x concentrations has impeded efforts to quantify this process. Recent measurements of stratospheric nitrogen dioxide from ground-based stations as well as aircraft and balloons have provided a first approximation to a global distribution of NO2 vertical columns at sunset. These observed vertical columns have been translated into time-dependent vertical NO2 profiles by means of a one-dimensional atmospheric photochemical model. Using recent observations of air temperature and ozone along with this information, the independent instantaneous (one second) rates of ozone production from oxygen photolysis P(O3), of ozone destruction from pure oxygen species (Chapman reactions) L(O x ), and of ozone destruction by nitrogen oxides L(NO x ) were estimated over the three-dimensional atmosphere. These quantities are displayed as zonal average contour maps, summed over various latitude zones, summed over various altitude bands, and integrated globally between 15 and 45 km. Although the global summation between 15 and 45 km by no means tells the complete story, these numbers are of some interest, and the relative values are: P(O3), 100; L(O x ), 15; L(NO x ), 45±15. It is to be emphasized that this relative NO x contribution to the integrated ozone balance is not a measure of the sensitivity of ozone to possible perturbations of stratospheric NO x ; recent model results must be examined for current estimates of this sensitivity.  相似文献   

13.
Diurnal variations in the vertical ozone density distribution have been calculated for the height range 40–150 km by extending our existing computer programs. The steady-state profiles were first calculated for fifteen constituents in the original program and three additional constituents (CH4, CO and CO2); the result was used as the initial condition for the time-dependent solution. The profile of the eddy diffusion coefficient used in this study was determined by comparing the model profile with the observations for CH4, whose density distribution is verysenstive to the eddy diffusion coefficient The effects of hydrogen and nitrogen compounds on the ozone density are discussed somewhat quantitatively; they reduce the ozone density mainly in the mesosphere and stratosphere, respectively. Special attention is given to the large depression of the ozone density at around 70–85 km, which has been obtained in many theoretical models but has neither been explained nor definitely confirmed by observations. Our time-dependent model indicates that the depression develops at night by the effect of hydrogen-oxygen and nitrogen-oxygen reactions and of eddy diffusion transports. The latter effect also produces an increase of the ozone density after midnight at some heights in the depression region.  相似文献   

14.
In a previous work, the stratospheric effect of a future supersonic aircraft fleet on ozone has been simulated, by using a photochemical diffusive 1D model and a 2D photochemical, radiative dynamical model. The fleet scenario was defined by Aerospatiale and Snecma for a current technology Mach-2 aircraft; the models were limited to simplified homogeneous phase reactions. The results indicated a global ozone decrease of about 1.5% in steady-state conditions. Now the 2D model has been upgraded and includes the classical heterogeneous reactions with Polar Strato- spheric Clouds (PSC) and aerosol. It also takes into account the natural or anthopogenic evolution of the background atmosphere. The scenario has been optimized to meet more realistic conditions. Thus, new results are presented. The main conclusion concerning the calculated impact of a realistic fleet for the next 20–50 years is still weaker than in the previous work: the decrease for the total ozone would always be lower than 0.3%. These results are commented, with the help of a parametric study, pointing out the importance of the background atmosphere and especially the total chlorine loading and the aerosol surface area.  相似文献   

15.
The dispersion of exhaust products of rocket fuel in the direction perpendicular to the motion of a rocket is investigated in this work. A comparison of the results of numerical calculations with a self-similar approximation of a strong cylindrically symmetric explosion is fulfilled. It is shown that at sufficiently high rocket velocity V ∞, which exceeds the sum of gas exhaust velocity V e from the nozzle and sound speed V s (V ∞ > V e +V s ), a gasdynamic hole can arise around the rocket trajectory in the upper atmosphere, inside which the total concentration of gas becomes less than the equilibrium concentration of gas at a given altitude. The dynamics of the profiles of density and temperature of the exhaust products inside a rocket plume is calculated.  相似文献   

16.
—This paper deals with a new broadband atmospheric model designed for predicting the total and diffuse solar radiation incident on the earth’s surface in medium or large-sized coastal or near-coastal cities, under a clear or cloudy sky. The revised solar spectrum is used. The atmospheric transmittance of each atmospheric parameter contributing to solar radiation depletion, water vapor, ozone, uniformly mixed gases, molecules and aerosols, is calculated using parameterized expressions resulting from integrated spectral transmittance functions. The beam and diffuse radiation components are obtained as a function of the specific atmospheric transmittances. The model requires the following parameters as inputs: total water vapor and ozone amount in a vertical column, sunshine duration and the surface albedo. The model has been used for validation purposes at two stations with slightly different characteristics (NOA and Penteli) in the Athens basin, where total and diffuse radiation measurements are available, for a period of 34 months for NOA and 23 for Penteli. The NOA station is located on a small hill (107 m a.m.s.l.) near the center of Athens, while the Penteli station (500 m a.m.s.l.) is situated in a relatively less polluted area in northern Athens. The clear sky part of the model was tested for 70 individual “clear” days with 2-minute intervals, while the whole model was checked with monthly “mean” days and mean hourly values. A close agreement between the calculated and the measured values of total and diffuse solar radiation is observed.  相似文献   

17.
We have studied the effects on the ozone concentration and surface temperature, of perturbations in the atmospheric content of nitrous oxide, methane, carbon dioxide and chlorofluorocarbons (CFC). The sensitivity study has been carried out with a radiative-convective-photochemical model. The doubling of carbon dioxide concentration has the effect of warming the troposphere and cooling the stratosphere. As a result of this cooling, the change of ozone columnar density produced by 10 ppb of chlorine amount to 9.3% as compared to –10.9% obtained without temperature feedback. Perturbation in nitrous oxide correspond to an increase in NO x of the stratosphere with consequent ozone reduction while doubling the methane concentration correspond to a slight increase in columnar density. The effect of the increased methane concentration in the stratosphere contributes to reduce the effect of CFC due to the enhanced formation of HCl. The perturbation of these two minor constituents appreciably increase the greenhouse effect to 2.30 from 1.67°, obtained when carbon dioxide alone is considered.  相似文献   

18.
Infrared (IR) molecular spectroscopy is proposed to perform remote measurements of NOx concentrations in the exhaust plume and wake of aircraft. The computer model NIRATAM is applied to simulate the physical and chemical properties of the exhaust plume and to generate low resolution IR spectra and synthetical thermal images of the aircraft in its natural surroundings. High-resolution IR spectra of the plume, including atmospheric absorption and emission, are simulated using the molecular line-by-line radiation model FASCODE2. Simulated IR spectra of a Boeing 747–400 at cruising altitude for different axial and radial positions in the jet region of the exhaust plume are presented. A number of spectral lines of NO can be identified that can be discriminated from lines of other exhaust gases and the natural atmospheric background in the region around 5.2 µm. These lines can be used to determine NO concentration profiles in the plume. The possibility of measuring nitrogen dioxide NO2 is also discussed briefly, although measurements turn out to be substantially less likely than those of NO. This feasibility study compiles fundamental data for the optical and radiometric design of an airborne Fourier transform spectrometer and the preparation of in-flight measurements for monitoring of aircraft pollutants.  相似文献   

19.
A one-dimensional atmospheric photochemical model with an altitude grid of about 1.5 km was used to examine the structure of the global mean vertical ozone profile and its night-time-to-daytime variation in the upper atmosphere. Two distinct ozone layers are predicted, separated by a sharp drop in the ozone concentration near the mesopause. This naturally occurring mesopause ozone deep minimum is primarily produced by the rapid increase in the destruction of water vapour, and hence increase in HOx, at altitudes between 80 and 85 km, a region where water-vapour photodissociation by ultraviolet radiation of the solar Lyman-alpha line is significant, and where the supply of water vapour is maintained by methane oxidation even for very dry conditions at the tropospheric-stratospheric exchange region. The model indicates that the depth of the mesopause ozone minimum is limited by the efficiency with which inactive molecular hydrogen is produced, either by the conversion of atomic hydrogen to molecular hydrogen via one of the reaction channels of H with HO2, or by Lyman-alpha photodissociation of water vapour via the channel that leads to the production of molecular hydrogen. The ozone concentration rapidly recovers above 85 km due to the rapid increase in O produced by the photodissociation of O2 by absorption of ultraviolet solar radiation in the Schumann-Runge bands and continuum. Above 90 km, there is a decrease in ozone due to photolysis as the production of ozone through the three-body recombination of O2 and O becomes slower with decreasing pressure. The model also predicts two peaks in the night-time/daytime ozone ratio, one near 75 km and the other near 110 km, plus a strong peak in the night-time/daytime ratio of OH near 110 km. Recent observational evidence supports the predictions of the model.  相似文献   

20.
Siberian gas venting and the end-Permian environmental crisis   总被引：1，自引：0，他引：1  
The end of the Permian period is marked by global warming and the biggest known mass extinction on Earth. The crisis is commonly attributed to the formation of the Siberian Traps Large Igneous Province although the causal mechanisms remain disputed. We show that heating of Tunguska Basin sediments by the ascending magma played a key role in triggering the crisis. Our conclusions are based on extensive field work in Siberia in 2004 and 2006. Heating of organic-rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion. Basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated > 100,000 Gt CO2. The gases were released to the end-Permian atmosphere partly through spectacular pipe structures with kilometre-sized craters. Dating of a sill intrusion by the U–Pb method shows that the gas release occurred at 252.0 ± 0.4 million years ago, overlapping in time with the end-Permian global warming and mass extinction. Heating experiments to 275 °C on petroleum-bearing rock salt from Siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases. The results indicate that global warming and ozone depletion were the two main drivers for the end-Permian environmental crisis. We demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a Large Igneous Provinces causes an environmental crisis or not. We propose that a similar mechanism could have been responsible for the Triassic-Jurassic (~ 200 Ma) global warming and mass extinction, based on the presence of thick sill intrusions in the evaporite deposits of the Amazon Basin in Brazil.  相似文献   

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