摘要:

A state‐of‐the‐art gas phase chemical mechanism for modeling atmospheric chemistry on a regional scale is presented. The second generation Regional Acid Deposition Model (RADM2) gas phase chemical mechanism, like its predecessor RADM1, is highly nonlinear, since predicted ozone, sulfate, nitric acid and hydrogen peroxide concentrations are complicated functions of NOxand nonmethane hydrocarbon concentrations. The RADM2 chemical mechanism is an upgrade of RADM1 in that (1) three classes of higher alkanes are used instead of one, (2) a more detailed treatment of aromatic chemistry is used, (3) the two higher alkene classes now represent internal and terminal alkenes, (4) ketones and dicarbonyl species are treated as classes distinct from aldehydes, (5) isoprene is now included as an explicit species, and (6) there is a more detailed treatment of peroxy radical‐peroxy radical reactions. As a result of these improvements the RADM2 mechanism simulates the concentrations of peroxyacetyl nitrate, HNO3, and H2O2under a wide variety of environmental conditions. Comparisons of RADM2 mechanism with the RADM1 mechanism predictions and selected environmental chamber experimental results indicate that for typical atmospheric conditions, both mechanisms reliably predict O3, sulfate and nitric acid concentrations. The RADM2 mechanism gives lower and presumably more realistic predictions of H2O2because of its more detailed treatment of peroxy radical‐peroxy radical

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16343

年代:1990

数据来源: WILEY

摘要:

We have evaluated the aerosol passing efficiency of a variety of inlet systems during three experiments on the National Center for Atmospheric Research Electra. During the Dynamics and Chemistry of the Marine Stratocumulus (DYCOMS) program, we found discrepancies between concentrations in cloud water and the air below cloud, which we attribute to curved‐inlet aerosol losses. In the First ISCCP Regional Experiment (FIRE) program, the same curved inlet passed significantly less material than a straight one. In the Particulate Matter Airborne Sampling Inlet Experiment (PASIN), we analyzed the material deposited within one inlet tube to establish an efficiency reference. Six different inlets were used simultaneously with six filter samplers to evaluate the effects of tube diameter, radius of curvature, and surface coating. The PASIN filters collected different amounts of material when they should have been sampling the same aerosol. Extraction of the 1‐inch metal reference tube routinely found that 50–90% of the aerosol material had been deposited in the tube. None of the inlets had an average bulk efficiency greater than about 50% for the aerosol species we measured. In the commonly used 1‐inch ID curved tube inlet, only 10–20% of marine sodium made it to the filter. High turbulence in the diffuser cone may be responsible for much of the observed loss. It is possible that many of the existing aircraft‐derived aerosol data in the literature are serious underestimates of actual ambient concentrations. We suggest some changes in strategy to improve the collection of aerosols fr

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16369

年代:1990

数据来源: WILEY

摘要:

We have analyzed solar spectra obtained with the 1‐m Fourier transform spectrometer on Kitt Peak for absorption by N2O and CO. During the period 1979–1985 we find that N2O shows no detectable seasonal variation or trend and can place an upper limit on the growth rate of 1. ppb per year. This is consistent with results of ground level gas sampling. For CO we see a large seasonal variation, but because of inadequate sampling we cannot detect a trend. Combined with other Spectroscopic studies, our mean CO level suggests a northern hemisphere tropospheric scale height for CO of ∼3

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16383

年代:1990

数据来源: WILEY

摘要:

Measurement of the background levels and study of the chemistry of trace organic carbon species in the remote marine troposphere occurred during an April–July 1987 SAGA II cruise in remote regions of the Pacific and Indian Oceans. Measured compounds included carboxylic acids, formaldehyde, light hydrocarbons (C2–C4), and ozone. The results show seasonal, diel, and spatial dependencies for the organic acids. Distinct latitudinal gradients are seen for most sampled compounds. Formic acid is well correlated with suspected precursors, formaldehyde and light hydrocarbons. Acetic acid follows a similar pattern as formic acid, although its precursors are as yet undefined. Diel patterns of low amplitude for the organic acids in the remote marine troposphere suggest a natural contribution to tropospheric photochemistry, and to the global carbon cycle as well. For the northern hemisphere Pacific Ocean, the mean formic acid mixing ratio was 0.80±0.30 ppbv, the mean acetic acid value was 0.78±0.32 ppbv. For the southern hemisphere Pacific Ocean, formic acid averaged 0.22±0.13 ppbv, for acetic acid, the mean was 0.28±0.18 ppbv. For the northern hemisphere Indian Ocean, the mean formic acid mixing ratio was 0.75±0.24 ppbv, and the mean acetic acid value was 0.69±0.27 ppbv. For the southern hemisphere Indian Ocean, the mean formic acid value was 0.19±0.17 ppbv, and the mean acetic acid value was 0.29±0.16 ppbv. Highest levels of organic acids were encountered near known anthropogenic source regions, in air masses of continental origin, or near regions of naturally produced alkenes (C2, C3). The ozone‐alkene oxidation scheme appears to play a major role in gas phase organic acid production in the remote marine troposphere. Nighttime gas phase deposition of the organic acids onto the ocean surface appears to be

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16391

年代:1990

数据来源: WILEY

摘要:

In April and May of 1988 along 170°W from 53°N to 14°S, simultaneous concentration measurements were made of the major components of the sulfur and reduced nitrogen cycles. The species measured included sea water dimethylsulfide, DMS (s), and total ammonia, NH3(s,tot) = NH3(s) + NH4+(s); atmospheric gas phase DMS (g), NH3(g), and SO2(g); and atmospheric particulate phase NH4+(p), non‐seasalt sulfate, nss SO4=(p), and methanesulfonate, MSA (p). Based on isentropic calculated back trajectories at 1000, 950, 850, and 700 mbar arrival heights, three apparent air mass regimes were encountered; one from 50°N to 30°N which recently had been in contact with Asia, one from 29°N to 15°N which had passed over Hawaii during a volcanic eruption several days earlier, and one from 14°N to 11°S which was the most representative of remote marine air. Changes in the relative concentrations of the atmospheric S and NH3species reflected the origin of the air masses sampled. The NH3(g) concentrations were low over the entire region studied, indicating that the lifetime of NH3in the marine boundary layer is on the order of hours. These low NH3concentrations led to only partially neutralized sulfate aerosol particles. The mean NH4+(p) to nss SO4=(p) molar ratio was 1.3±0.71. The highest ratios were found in continentally influenced air masses where the NH4+(p) was most likely of continental origin and in remote marine air masses with an absence of continentally derived nss SO4=(p). The lowest ratios found were a result of high nss SO4=(p) concentrations in air masses influenced by the Hawaiian volcanic plume. Seawater concentrations of DMS (s) and NH3(s,tot) were lowest in the North Pacific central gyre and highest in the northern latitudes and near and south of

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16405

年代:1990

数据来源: WILEY

摘要:

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1700‐km reach of the river during the low‐water period of the annual flood cycle (November–December 1988). Overall, emissions averaged 68 (±20) mg CH4m−2d−1and were significantly lower than similar emissions determined previously for the high‐water period, 184 (±41) mg CH4m−2d−1(July–August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low‐water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emissions from eight lakes located in the central Amazon basin showed similar results. Average annual emission from the lakes was 125 (±28) mg CH4m−2d−1. Methane emissions from lakes were significantly higher during the high water period, again primarily due to an increase in emissions from macrophyte habitats. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg yr−1, which indicates the importance of the area in

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16417

年代:1990

数据来源: WILEY

摘要:

Laser‐generated interference in the laser‐induced fluorescence detection of tropospheric hydroxyl is addressed by a detailed photochemical model. This phenomenon arises through photolysis of ozone by the detection laser and subsequent reaction of O(1D) with H2O to form OH. The approach is direct time integration of the coupled differential equations describing the pertinent chemical reactions, collisional energy transfer, and photolytic and spectroscopic processes, including an assessment of limitations due to uncertainties in the input parameters. The goal is to use the model to quantitatively design OH detection methods so that the experimental results need not rely on such a model for interpretation. Previously reported measurements of tropospheric OH appear to have been contaminated by ozone interference effects and by optical saturation of the monitoring transition. However, suggested improvements can reduce the problem to interference levels below 2×105OH molecules/cm3, permitting measurements useful for testing theories of fast tropospheric photochemi

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16427

年代:1990

数据来源: WILEY

摘要:

Carbon monoxide mixing ratios obtained by the October 1984 Measurement of Air Pollution from Satellites (MAPS) experiment are compared with the distribution of October 1984 Total Ozone Mapping Spectrometer (TOMS) ozone concentrations. The TOMS and MAPS data show coincident high values of ozone and carbon monoxide over central South America and southeastern Africa. The 1984 MAPS data are also compared with tropospheric ozone concentrations derived from 6 years of TOMS and Stratospheric Aerosol and Gas Experiment (SAGE) I and II measurements. Examination of the October climatological distribution of tropospheric ozone also reveals high concentrations over central South America and southeastern Africa. These coincident high values of CO and ozone in the rural southern tropics are most likely due to biomass burning and the subsequent transport of CO and ozone by large‐scale weather patterns. It appears that both CO and ozone are being transported thousands of kilometers from their source regions by the prevailing wind

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16443

年代:1990

数据来源: WILEY

摘要:

The artificially ionized layers in the atmosphere caused by microwave pulses are actively studied for possible application to communication services. The possible negative influences of this project on the environment will be considered. They are connected with the synthesis of nitric oxide, which is aggressive to the ozone layer. The mechanism of nitric oxide synthesis in the ionized region is based on the chemical reactions of molecules and atoms in the metastable electronic states excited by electron impact. These reactions are effective under conditions which are optimum for the formation of an artificially ionized layer. The concentration of nitrogen oxide produced in the ionized region is estimated for a variety of parameters of microwave pulses which can be used for breakdown of the atmosphere. The spatial shape of the artificial NOxcloud formed by the atmospheric wind and diffusion is studied. Artificially ionized layers are considered as the anthropogenic source of NOxon an annual global basis and compared to the existing natural sources. It is shown that the worldwide net of these layers does not appear to be sufficient to be of environmental concern.

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16451

年代:1990

数据来源: WILEY

摘要:

Atomic oxygen and atomic hydrogen have been inferred from the hydroxyl airglow measurements on Solar Mesosphere Explorer (SME) spacecraft between 0.01 and 0.0013 mbar (80–93 km). This constitutes the first measurements of the seasonal and latitudinal variations of these atomic species, in the mesopause region. At night, atomic oxygen is directly proportional to the Meinel band emission of OH. During the day the emission is proportional to the product of ozone and hydrogen. Since daytime ozone is inferred from the O2(1Δg) emission, daytime hydrogen can be inferred. Daytime atomic oxygen is then inferred from the measured hydrogen and ozone. At levels where atomic oxygen is found by both methods (at 0.0032–0.0013 mbar or 88–93 km) the day and night atomic oxygen display the same relative seasonal variations. Very large annual and semiannual changes are found in the atomic hydrogen density between 80 and 93 km. At 40°N the summer‐to‐spring ratio of atomic hydrogen exceeds a factor of 4 at 0.01 mbar (80 km). Between 80 and 90 km the odd oxygen family is found to be almost entirely atomic oxygen. Its behavior is characterized by annual variations at 40° north and south and semiannual changes at the equator; in both cases the changes are a doubling from minimum to maximum. At least part of the mid‐latitude semiannual variation in ozone is found to be due to the product of two annually varying functions. The atomic oxygen is annual and maximizes in the winter while the ozone‐oxygen partitioning, controlled mostly by temperature, maximizes in the summer due to tem

ISSN:0148-0227    

DOI:10.1029/JD095iD10p16457

年代:1990

数据来源: WILEY