摘要:

Photochemical calculations along “diabatic trajectories” in the meridional plane are used to search for the cause of the dramatic springtime minimum in Antarctic column ozone. Results indicate that the minimum is principally due to catalytic destruction of ozone by high levels of total odd nitrogen which are in accord with column sum observations of NO2(between 20 and 35 km) made in the Antarctic. Calculations suggest that these levels of odd nitrogen are transported to the lower stratosphere from the mid to upper stratosphere and lower mesosphere. This transport occurs within the polar vortex and during the polar night. The possibility that these odd nitrogen levels are related to the 11‐year solar cycle and are increased by enhanced formation in the thermosphere and mesosphere during solar maximum conditions is discussed. Analysis of satellite data (LIMS, SME, SAGE, SAGE II) establishes significantly increased levels of stratospheric total odd nitrogen for the 1979–1984 time period, particularly at the midsouthern latitudes. Calculations suggest that these mid‐latitude increases in odd nitrogen contribute significantly to the recently reported mid‐latitude ozone decreases. The persistent reoccurrence of the Antarctic ozone minima into the mid‐1980s is related to this growth of odd nitrogen. Transient planetary wave activity near the onset of the final warming is found to significantly moderate the formation of the minimum in column ozone. Chlorine species at double the present atmospheric levels are shown to have an insignificant effect if only homogeneous processes are considered. If heterogeneous chlorine reactions are considered, the catalytic destruction of ozone by the odd nitrogen is slightly inhibited between 20 and 30 km. Below 20 km the catalytic destruction of ozone due to an odd hydrogen and odd chlorine cycle may be fostered by the heterogeneous reactions but this cycle contributes only modestly to the calculated ozone column su

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10771

年代:1986

数据来源: WILEY

摘要:

Atmospheric Lifetime Experiment measurements of CFCl3and CF2Cl2several times per day at five remote surface sites from July 1978 to June 1983 are reported. For January 1, 1981, the mean latitudinally averaged mixing ratios were 177.5 parts per trillion by volume (pptv) and 300.4 pptv for CFCl3and CF2Cl2, respectively. The atmospheric content at that time is estimated to have been 3,960 million kg of CFCl3and 6,000 million kg of CF2Cl2. The mixing ratios exhibited an annual rate of increase of 9.0 and 15.3 pptv/yr for CFCl3and CF2Cl2, respectively. Trend lifetime estimates for January 1, 1981 from this 5‐year data set are 74−17+31years for CFCl3and 111−44+222years for CF2Cl2. On the basis of a comparison of CFCl3data on two different chromatographic columns, it is shown that the spectrum of measurement errors maximizes at low frequencies but may be relatively flat at periods longer than approximately 3 years. The uncertainties in the trend lifetime estimates are, however, dominated by release uncertainties. Inverting the analysis, assuming stratospheric photodissociation to be the only atmospheric sink of fluorocarbons, yields annual release estimates with an accuracy, based on the precision of the measurement system, of approximtely 8%. Excellent agreement with the Chemical Manufacturers Association release estimates is found for CFCl3; for CF2Cl2the estimates, although exhibiting variability from year to year, suggest that the emissions in the USSR and Eastern Europe have remained roughly constant over the years 1979

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10797

年代:1986

数据来源: WILEY

摘要:

From the observations of atomic oxygen concentrations during the Energy Budget Campaign 1980, heating rates in the lower thermosphere at high latitude for late fall are derived and are found to be rather high. Useful information is also inferred for the vertical transport of mass and heat at these heights. The eddy diffusion coefficient which is derived from the data decreases with decreasing altitude below 100 km and reaches a minimum value of the order of 10 m2s−1near the mesopause. Such low value implies a low minimum concentration of nitric oxide (105–106cm−3) near

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10818

年代:1986

数据来源: WILEY

摘要:

The ozone distribution and its variability is simulated with a general circulation model (GCM), which includes self‐consistent representation of the physical processes and an accurate parameterization of the ozone photochemical sources and sinks. Emphasis is placed on analysis of the action of atmospheric waves on the O3distribution. In particular, the model generates the medium‐scale waves which are often observed in the southern hemisphere. These waves tend to form quasi‐regular O3patterns with zonal wave numbers 4, 5, and 6, in fairly good agreement with the observations. Baroclinic instability generates the waves in the lower troposphere, but it is their equivalent barotropic structure in the upper troposphere‐lower stratosphere which produces the signal on the total ozone column, since O3disturbances are nearly in phase in this altitude range. Episodes of large amplitude of the medium‐scale waves occur when the transient waves interact with a stationary wave. This standing wave has a zonal wave number close to 4 and appears to result from the large convective activity within the South Pacific Convergence Zone and its southward extension at mid‐latitudes. This study gives a good illustration of the important role played by GCMs in understanding the interactions between dynamical and physical processes in the troposphere and wave activity and O3distribution in the lower s

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10825

年代:1986

数据来源: WILEY

摘要:

It is well established that plants tend to increase net photosynthesis under increased carbon dioxide. It is also well established that a large fraction of atmospheric methane is produced by microbial metabolism of organic sediments in paddies and freshwater wetlands, where a major source of organic debris is local plant growth. As CO2increases, it may lead to increased methane production and a resulting enhancement of the expected greenhouse warming. A rough estimate of the present rate of this biologically mediated feedback on the climate system indicates that it might account for as much as 30% of the observed methane increase and speed up the greenhouse forcing by as much as 15%.

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10847

年代:1986

数据来源: WILEY

摘要:

A photochemical model is used to predict temporal trends in OH, CH4, and CO over the next 50 years and to assess possible past changes in these trace gases from 1860 to 1985. Various scenarios of perturbed CH4and CO levels based on recently reported CH4and CO data are simulated at several levels of background NOx. With low NOxconditions (NO + NO2= 25 pptv (parts per trillion by volume)), typical of the nonpolluted troposphere, we compute a monotonic loss of tropospheric OH from 1860 to 2035, with the magnitude of the decrease dependent on CO and CH4increases during the period. If current trends continue (ground‐level mixing ratios (mole fractions) of CH4rising about 1% per year), by 2035 northern latitude CH4will increase from 1.6 to 2.9 ppmv (parts per million by volume) and CO will double or triple its present day level (to about 250–350 ppbv (parts per billion by volume) in the nonpolluted northern hemisphere). The column abundance of OH in the background troposphere will decrease 25–35%, depending on the magnitude of CH4and CO increases and assuming that global temperature increases do not raise water vapor levels during that time. Calculations with increased H2O show a 17–30% decrease in OH. Under higher‐NOxconditions (1 ppbv), OH shows a decline from 1860 to 2035, but it shows only half as much decline as with low‐NOxconditions. In the case of NOxin a transitional zone (i.e., NOxincreasing from 20 pptv in 1860 to 0.5 ppbv in 2035), CO and CH4increases accompany a rise in OH, followed by a small decline. The turning point in OH depends on the rate of change in NOxand O3. Recently observed upward trends in CO and CH4are probably due to increasing emissions of both CH4and CO. We always compute a temporal increase in tropospheric O3when CH4and CO increase. Typical 1860 values for surface O3are 25 ppbv, compared to 30 ppbv (NOx= 25 pptv)and 40 ppbv (NOx= 1 ppbv) in 1985. In a transition NOxzone we find surface O3increasing from 10 ppbv in 1860 to 27 p

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10853

年代:1986

数据来源: WILEY

摘要:

Mixing ratios of tropospheric carbon monoxide measured by a gas filter radiometer carried aboard the space shuttle during November 1981 are reported. The data represent average mixing ratios in the middle and upper troposphere between 38°N and 38°S latitude. Approximately 10,000 individual measurements were obtained in each of the two channels of the instrument. The data are presented in the form of plots that show the individual carbon monoxide mixing ratio measurements as a function of latitude and longitude and in the form of maps that show the data averaged over 5° latitude by 5° longitude squares. The data show relatively little variation in the mixing ratio in the southern hemisphere; however, the data from both the tropics and the northern hemisphere show strong gradients with both latitude and longit

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10865

年代:1986

数据来源: WILEY

摘要:

Boundary layer gas phase concentrations of H2O2and CH3OOH are calculated using a multilevel Lagrangian photochemical model. A range of emission conditions and resultant pollutant levels are considered, such as occur in the northeastern United States during summer months. The dependence of peroxide concentrations on chemical rate constants and meteorological variables is analyzed in terms of a budget equation for the formation and removal of radicals in the atmosphere. For representative summer conditions (solar intensity, humidity, and ambient O3level) the production of radicals, primarily from photolysis of O3, occurs significantly faster than the average NOxemission rate in the northeastern United States. A necessary condition of this imbalance is that only a fraction of the radicals introduced into the atmosphere can be removed by reactions with NO and NO2. The remaining radicals are removed primarily by recombination reactions forming peroxides. Variations in radical production, such as might reasonably be caused by changes in precursor concentration, latitude, season, cloud cover and/or humidity, can reverse the sense of the inequality between NOxemissions and radical production and lead to an order of magnitude decrease in the amount of peroxides formed.

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10889

年代:1986

数据来源: WILEY

摘要:

A chemical mechanism for the gas phase atmospheric oxidation of nitrogen oxides (NOx) and sulfur dioxide (SO2) in the presence of reactive hydrocarbons (RHC) has been developed for use in long‐range transport modeling. The mechanism includes numerous reactions important for nighttime and multiday simulations which have been previously ignored in photochemical mechanisms designed for urban scale applications. This mechanism is capable of simulating the decay of NOx/SO2/RHC precursors and the formation of oxidation products such as nitric acid, sulfuric acid, ozone, hydrogen peroxide, hydroperoxides, and organic peroxides which have recognized roles in the acidification of precipitation. Testing of detailed and condensed versions of the chemical mechanism is reporte

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10905

年代:1986

数据来源: WILEY

摘要:

The balloon‐borne, vertical‐wire antenna system used for measurement of the atmospheric conduction current above the boundary layer of the earth was introduced by Kasemir (1960) and has been utilized by several investigators to measure globally representative values of the air‐earth current. The values of the atmospheric conduction current density measured by this technology and presented in the literature (∼2 pA/m2) ought to be multiplied by a factor of 2 to correct for physical processes at the antenna boundary. An analysis of the interaction of the balloon‐borne, vertical‐wire antenna with the atmospheric electrical environment shows that this technology can be employed to produce reliable measurements of the atmospheric conduction current; however, some of the reported measurements exhibit a possible deviation in performance, some of which can be explained by our analysis. The solution for the conducting spheroid is further developed in the appendix to obtain additional results. Analytical solutions are found for the electric field, conductor charging, and current measurements when the polar conductivities are unequal. Electric field enhancement factors for spheroids and approximate solutions for spheroids and other elongated objects are given. The distribution of induced charge along the axis of spheroids is shown to be linear and the solution indicates a similar induced charge distribution along all long conductors. The theory indicates that the 45° cone of protection rule probably overestimates the area protected by tal

ISSN:0148-0227    

DOI:10.1029/JD091iD10p10937

年代:1986

数据来源: WILEY