Showing papers by "Paul J. Crutzen published in 1988"
TL;DR: In this paper, the authors focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises.
Abstract: There is increasing evidence that at polar sunrise sunlight-induced changes in the composition of the lower Arctic atmosphere (0–2 km) are taking place that are important regarding the tropospheric cycles of ozone, bromine, sulphur oxides1, nitrogen oxides2 and possibly iodine3. Here we focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises. The destruction might be linked to catalytic reactions of BrOx radicals and the photochemistry of bromoform, which appears to have a biological origin in the Arctic Ocean. This may clarify previously unexplained regular springtime occurrences of ozone depletion at ground level in a 10-year data record at Barrow, Alaska4, as well as peaks in aerosol bromine observed throughout the Arctic in March and April3. Current information does not allow us to offer more than a speculative explanation for the chemical mechanisms leading to these phenomena.
939 citations
01 Jan 1988
TL;DR: Although only about 10% of all atmospheric ozone is located in the troposphere, it is the main driver of the photochemical processes which lead to the recycling of most of the gases that are emitted into the atmosphere by natural processes and anthropogenic activities as discussed by the authors.
Abstract: Although only about 10% of all atmospheric ozone is located in the troposphere, it is the main driver of the photochemical processes which lead to the recycling of most of the gases that are emitted into the atmosphere by natural processes and anthropogenic activities.
197 citations
TL;DR: In this paper, the authors focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises.
Abstract: There is increasing evidence that at polar sunrise sunlight-induced changes in the composition of the lower Arctic atmosphere (0–2 km) are taking place that are important regarding the tropospheric cycles of ozone, bromine, sulphur oxides1, nitrogen oxides2 and possibly iodine3. Here we focus on recent ground-level observations from the Canadian baseline station at Alert (82.5° N, 62.3° W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises. The destruction might be linked to catalytic reactions of BrOx radicals and the photochemistry of bromoform, which appears to have a biological origin in the Arctic Ocean. This may clarify previously unexplained regular springtime occurrences of ozone depletion at ground level in a 10-year data record at Barrow, Alaska4, as well as peaks in aerosol bromine observed throughout the Arctic in March and April3. Current information does not allow us to offer more than a speculative explanation for the chemical mechanisms leading to these phenomena.
171 citations
TL;DR: In this article, a coupled climate and chemistry model has been developed to estimate past and possible future changes in atmospheric temperatures and chemical composition due to human activities, and the model takes into account heat flux into the oceans and uses a new tropospheric temperature lapse rate formulation.
Abstract: A one-dimensional coupled climate and chemistry model has been developed to estimate past and possible future changes in atmospheric temperatures and chemical composition due to human activities. The model takes into account heat flux into the oceans and uses a new tropospheric temperature lapse rate formulation. As found in other studies, we estimate that the combined “greenhouse effect” of CH4, O3, CF2Cl2, CFCl3 and N2O in the future will be about as large as that of CO2. Our model calculates an increase in average global surface temperatures by about 0.6°C since the start of the industrial era and predicts for A.D. 2050 a twice as large additional rise. Substantial depletions of ozone in the upper stratosphere by between 25% and 55% are calculated, depending on scenario. Accompanying temperature changes are between 15°C and 25°C. Bromine compounds are found to be important, if no rigid international regulations on CFC emissions are effective. Our model may, however, concivably underestimate possible effects of CFCl3, CF2Cl2, C2F3Cl3 and other CFC and organic bromine emissions on lower stratospheric ozone, because it can not simulate the rapid breakdown of ozone which is now being observed worldwide. An uncertainty study regarding the photochemistry of stratospheric ozone, especially in the region below about 25 km, is included. We propose a reaction, involving excited molecular oxygen formation from ozone photolysis, as a possible solution to the problem of ozone concentrations calculated to be too low above 45 km. We also estimate that tropospheric ozone concentrations have grown strongly in the northern hemisphere since pre-industrial times and that further large increases may take place, especially if global emissions of NOx from fossil fuel and biomass burning were to continue to increase. Growing NOx emissions from aircraft may play an important role in ozone concentrations in the upper troposphere and low stratosphere.
103 citations
TL;DR: In this paper, the authors measured arithmetic mean fluxes of N2O, CH4, and CO2 from undisturbed soil plots to the atmosphere were 2.5×109, 4.3×1010, and 3.0×1013 molecules cm-2 s-1, respectively.
Abstract: Emissions of N2O, CH4, and CO2 from soils at two sites in the tropical savanna of central Venezuela were determined during the dry season in February 1987. Measured arithmetic mean fluxes of N2O, CH4, and CO2 from undisturbed soil plots to the atmosphere were 2.5×109, 4.3×1010, and 3.0×1013 molecules cm-2 s-1, respectively. These fluxes were not significantly affected by burning the grass layer. Emissions of N2O increased fourfold after simulated rainfall, suggesting that production of N2O in savanna soils during the rainy season may be an important source for atmospheric N2O. The CH4 flux measurements indicate that these savanna soils were not a sink, but a small source, for atmospheric methane. Fluxes of CO2 from savanna soils increased ninefold two hours after simulated rainfall, and remained three times higher than normal after 16 hours. More research is needed to clarify the significance of savannas in the global cycles of N2O, CH4, CO2, and other trace gases, especially during the rainy season.
91 citations
TL;DR: In this article, the authors measured phosgene, a possible product from the oxidation of natural and industrial chlorinated hydrocarbons and which can oxidize further to form Cl Ox.
Abstract: Industrial chlorofluorocarbons have now accumulated so much in the atmosphere that the ClOx radicals produced from their oxidation are causing substantial reductions in the ozone layer. Here we measure phosgene, which is one possible product from the oxidation of natural and industrial chlorinated hydrocarbons and which can oxidize further to form ClOx. Our measurements show a mixing ratio of 17 p.p.t.v. in the upper troposphere, and an average of 22 p.p.t.v. in the lower stratosphere. These values are substantially greater than those estimated with a model that only considers the photochemical breakdown of CCl4, indicating the possible significance of other more reactive chlorocarbon compounds, especially CHCl3, CH3CCl3, C2HCl3 and C2Cl4 and their oxidation products in supplying chlorine to the lower stratosphere.
48 citations
TL;DR: In this article, the authors investigated the role of oxygen dimer (O/sub 2/) in reactions initiated by its photodissociation and found that ozone formation was linear with time even though its rate of photolysis exceeded the rate of its generation from oxygen.
Abstract: Ozone formation in the 214-nm photolysis of oxygen at pressures ranging from 380 to 1300 Torr was investigated. The rates of ozone formation increase with the square of oxygen pressure mirroring the pressure dependence of the absorption cross sections of oxygen. This observation demonstrates the importance of the collision-induced changes in oxygen absorbance and points to a need to examine the role of oxygen dimer (O/sub 2/) in reactions initiated by its photodissociation. Because of the high dilution of ozone, its formation was found to be linear with time even though, on the average, its rate of photolysis exceeded the rate of its generation from oxygen. The quantum yield of ozone formation was 1.86 /plus minus/ 0.17 independent of O/sub 2/ pressure. From this result the quantum yield of the primary process O/sub 2/ + hv (214 nm) ..-->.. 2O(/sup 3/P) is estimated as being equal to 0.93 /plus minus/ 0.08 (2sigma). Based on the observed linear buildup of ozone and on model calculations, an upper limit of about 0.03 is estimated for O/sub 3/ photolysis via a channel which leads to O(/sup 3/P) and an excited O/sub 2/ species that can regenerate ozone in its reaction with oxygen.
21 citations
6 citations