摘要:

Winds and convective mixing from a general circulation model of the atmosphere have been applied in a chemical tracer model (CTM) to simulate the global distribution and temporal variability of chlorofluorocarbons (CFCs). The seasonal cycle in moist convection, with maximum activity over continents in summer, leads to an annual cycle in the surface concentration of CFCs. Emissions are retained in the lowest levels of the atmosphere during winter, and surface concentrations peak near sources. In this season, CFCs from European sources are carried by low‐level winds into the Arctic. During summer, vertical exchange is more efficient, and pollutants are transported more rapidly to the middle atmosphere. Consequently, concentrations of CFCs during summer are relatively low near the surface and elevated in the middle troposphere. Time series analysis of data from Adrigole, Ireland, indicates that the model accurately simulates long‐range transport of air pollution. The model reproduces global distributions and trends for CFC‐11 and CFC‐12 observed by the ALE experiment; however, subgrid diffusion must be introduced into the model in order to reproduce the observed interhemispheric gradient. Interhemispheric exchange occurs mainly in the upper tropical troposphere, producing a profile which increases with altitude in the southern hemisphere, in agreement with observations. The distribution of CFCs is such that it is necessary to apply important corrections to observations at surface stations in order to derive global distri

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06579

年代:1987

数据来源: WILEY

摘要:

A three‐dimensional chemical tracer model for the troposphere is used to simulate the global distribution of85Kr, a long‐lived radioisotope released at northern mid‐latitudes by nuclear industry. Simulated distributions for the period 1980–1983 are in excellent agreement with data from six latitudinal profiles measured over the Atlantic. High concentrations of85Kr are predicted over the Arctic in winter, advected from European sources, and somewhat smaller enhancements arising from the same sources are predicted over the tropical Atlantic in summer. Latitudinal gradients are steepest in the northern tropics, with distinctly different seasonal variations over the Pacific, as compared to the Atlantic. The global inventory of85Kr is reconstructed for the period 1980–1983 by combining the concentrations measured over the Atlantic with the global distributions predicted by the model. The magnitude of the Soviet source is derived. The interhemispheric exchange time is calculated as 1.1 years, with little seasonal d

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06614

年代:1987

数据来源: WILEY

摘要:

Climatologies of total columnar ozone and integrated stratospheric ozone amounts at low latitudes (15°N to 15°S), derived from satellite observations, are presented. A significant longitudinal variability in total ozone is present, with highest values generally located between 60°W and 60°E. The integrated stratospheric component of total ozone, on the other hand, does not exhibit a longitudinal preference for high values. Therefore we hypothesize that the climatological longitudinal distribution of total ozone reflects the variability of the abundance of tropospheric ozone at low latitudes. Furthermore, we speculate that in situ photochemical production of ozone resulting from biomass burning may be responsible for the observed enhancement of total ozone at these longitu

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06627

年代:1987

数据来源: WILEY

摘要:

Pyruvic acid, a product of the atmospheric oxidation of cresols and probably of isoprene, has been determined together with formic acid in atmospheric aerosols and rain as well as in the vapor phase. Both acids are present predominantly as vapor; only about 10–20% of the total atmospheric pyruvate and 1–2% of the total formate are in the particulate phase. The concentrations of pyruvic and formic acid are highly correlated, with typical formic‐to‐pyruvic ratios of 10–30 in the gas phase, 20–30 in rain, and 2–10 in aerosols. The gas‐phase and rain ratios are comparable to those predicted to result from isoprene oxidation. Pyruvic acid levels were similar in the eastern United States (during summer) and the Amazon Basin, suggesting that natural processes, particularly the photochemical oxidation of isoprene, could account for most of the pyruvic acid present in

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06635

年代:1987

数据来源: WILEY

摘要:

A large discrepancy exists among recent estimates of the primary quantum efficiencies (ϕ1) of nitrogen dioxide photodecomposition, NO2+hν → NO + O(3P), in the wavelength range from 374 to 396 nm. To resolve this problem, quantum yields of formation of NO, O2, and NO2loss have been measured for NO2vapor at low pressures (0.13–0.30 torr) irradiated at selected wavelengths (334.1–404.3 nm) and temperatures (273–370 K). From these data, estimates of ϕ1were derived which confirm the previous findings of Jones and Bayes (1973b): ϕ1increases rapidly from near zero at 424 nm to near unity for excitation at λ397.9 nm (λdiss) is made up in large part from the rotational and vibrational energy of the NO2molecules. Recommended values for ϕ1based upon a review of these data and estimates made over a period of 58 years, are given as a functi

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06642

年代:1987

数据来源: WILEY

摘要:

During the STRATOZ III flights in June 1984, approximately 160 measurements of peroxyacetylnitrate (PAN) were made with a specially designed gas chromatograph on board the Caravelle 116 airplane. The measurements cover a latitude range from 70°N to 60°S and altitudes up to 12 km. The results show that PAN is present throughout the troposphere at low but measurable levels. Southern hemispheric data from clean marine air masses show levels of 7–10 ppt, with little variability up to about 10 km altitude. In the southern uppermost troposphere and lowest stratosphere a significant increase in PAN can be seen, indicating substantial in situ formation of PAN at these altitudes. The situation at lower latitudes in the northern hemisphere is similar as long as the air masses are free of anthropogenic influence. At mid and high northern latitudes, considerably higher PAN mixing ratios (sometimes more than 100 ppt) are found even outside continental areas. These data also show a rather high variability. This can be ascribed to the influence of North America and Europe as source areas for PAN and PAN precurs

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06653

年代:1987

数据来源: WILEY

摘要:

Atmospheric photochemistry models have been used to predict the sensitivity of the ozone layer to various perturbations. These same models also predict concentrations of chemical species in the present day atmosphere which can be compared to observations. Model results for both present day values and sensitivity to perturbation depend upon input data for reaction rates, photodissociation rates, and boundary conditions. This paper develops a method of combining the results of a Monte Carlo uncertainty analysis with the existing set of present atmosphere species measurements. The method is used to examine the range of values for the sensitivity of ozone to chlorine perturbations that is possible within the currently accepted uncertainty ranges for input data. It is found that model runs which predict ozone column losses much greater than 10% as a result of present fluorocarbon fluxes produce concentrations and column amounts in the present atmosphere which are inconsistent with the measurements for ClO, HCl, NO, NO2, and HNO3.

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06662

年代:1987

数据来源: WILEY

摘要:

The third‐order rate constants for NaOH + CO2+ M were measured in a flow tube at 298 K. The rate constants for N2and N2O buffer gases are (1.3±0.3) × 10−28and (2.9±0.6) × 10−28cm6molecule−2s−1, respectively. We expect the product of this reaction, NaHCO3, to be relatively stable with respect to 0 atom reaction and photolysis and to be a dominant reservoir species for Na in the mesosphere. The association reaction of NaOH with CO2is at least 40 times faster than NaOH + HCl at all altitudes below the Na layer. Na species will not affect stratospheric ClOxan

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06675

年代:1987

数据来源: WILEY

摘要:

We present the detailed results of ground‐based mesospheric water vapor measurements obtained by microwave spectroscopy at the Jet Propulsion Laboratory (JPL) from December 1984 to April 1985 (JPL 1984/85), and an overview of results obtained the previous year from April to June 1984 (published by Bevilacqua et al., 1985). The JPL 1984/85 spectral data appeared to contain an instrumental baseline curvature which we were able to bracket and remove. In general, the JPL 1984/85 results are in good agreement with those of our previous measurements. They indicate water vapor mixing ratios between 6 and 8 ppmv at 60 or 65 km and falling off steeply with height above this point to values of less than 2 ppmv at 80 km. In addition, there is a large amount of day‐to‐day variability indicated in the data. A major result of the study is that we find that both the observed vertical gradient of water vapor mixing ratio and its seasonal variation are consistent with the hypothesis that vertical transport time scales are smaller, perhaps by an order of magnitude, than values currently used in both one‐ and two‐dimensional photochemical/dynamic

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06679

年代:1987

数据来源: WILEY

摘要:

Ground‐based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70‐ to 85‐km region of ≲(1–2) × 105cm2s−1during spring through summer at mid‐latitudes. Although chemical acceleration of vertical transport is substantial for O and O3below the mesopause, the divergences of their associated fluxes are modest, with at most a factor of 2 effect on the concentrations of O and O3for measured variability in gravity wave activity. Comparison of Solar Mesosphere Explorer (SME) O3data with model results reinforces the conclusions of slow vertical mixing in the upper mesosphere as a consequence of the reduced HOxcatalytic loss of odd oxygen. The changes in chemical rate constants recommended by Rusch and Eckman (1985), in conjunction with slow vertical mixing, yield good agreement with SME O3data. The slow vertical mixing deduced in this study is consistent with upper limits obtained from studies of the mesospheric heat budget and could be construed as evidence for an advectively controlled mesosphere. A comparison of the vertical eddy diffusion coefficients for momentum stresses, constituent transport, and heat transport suggests that the eddy Prandtl number must

ISSN:0148-0227    

DOI:10.1029/JD092iD06p06691

年代:1987

数据来源: WILEY