摘要:

We present an analysis of data for tropospheric ozone with a focus on spatial and temporal variations. Surface ozone at mid‐latitudes displays two modes of seasonal behavior: a broad summer maximum within a few hundred kilometers of populated and industrialized regions in Europe and the United States and a minimum in summer or autumn in sparsely populated regions remote from industrial activity‐in Tasmania and Canada for example. The current data base for different regions, in combination with limited historical data, indicates that summertime concentrations of ozone near the surface in rural areas of Europe and the central and eastern United States may have increased by approximately 6–22 ppb (20%–100%) since the 1940's. The seasonal cycle of ozone in the middle troposphere over Europe, the United States, and northern Japan is very similar to that at the surface with a summer maximum, but it is quite different from that at 300 mbar, which is characterized by a maximum in spring. There is good evidence for an increase in ozone in the middle troposphere over Europe during the past 15 years and weaker evidence for a similar increase over North America and Japan. The increase in tropospheric ozone contributes significantly to the trend in the column of ozone and may compensate for 20%–30% of the decrease in ozone in the stratosphere over middle and high latitudes of the northern hemisphere. We argue that the summer maximum in ozone and the observed trends are due to photochemical production associated with anthropogenic emissions of NOx, hydrocarbons, and CO from combustion of fossil fuels. A strong seasonal variation in ozone observed at Natal, Brazil (6°S), may also result from emissions of NOxand hydrocarbons, in this case from agricultural burning. Maximum concentrations at Natal are similar to values found at mid‐latitudes in summer. Tropical ozone exhibits strong spatial and temporal

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10463

年代:1985

数据来源: WILEY

摘要:

Distributions of the ambient atmospheric mixing ratios of OCS and CS2were determined from grab samples collected at altitudes ranging from 6 to 8 km (20,000 to 26,000 feet) during an aircraft flight between San Juan, Puerto Rico, and Albany, New York (July 11–12, 1982). No spatial variation is observed for OCS mixing ratios at these altitudes and latitudes within the uncertainty of the collection and analysis techniques. The average OCS mixing ratio is 517±65 pptv, where the standard deviation includes atmospheric as well as experimental variability. CS2values, on the other hand, show considerable spatial variability that may be correlated with intense local cumulonimbus activi

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10483

年代:1985

数据来源: WILEY

摘要:

The atmospheric flux of7Be over a 2‐year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm2(1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm−2d−1. Despite the different production‐source terms for7Be and210Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20–30%) in relation to inventories calculated from its depositional flux to bucket samplers. Possible explanations for this enrichment are that above‐ground vegetation is more efficient at collecting dry aerosols (containing short‐lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed210Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both7Be and210Pb in marsh cores are affected by the presence of vegetation and the location of the grou

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10487

年代:1985

数据来源: WILEY

摘要:

A one‐dimensional photochemical model has been used to estimate the flux of dissolved hydrogen peroxide (H2O2) and of other soluble species in rainwater as a function of atmospheric oxygen level. H2O2should have replaced O2as the dominant oxidant in rainwater at oxygen levels below 10−3–10−2times the present atmospheric level (PAL). The exact value ofpO2at which H2O2becomes more important than O2depends on the abundance of trace gases such as CO, CH4, and NO. H2O2was probably an important oxidant even in an O2‐free atmosphere, provided that CO2levels were significantly higher than today's. In model atmospheres containing free O2the concentration of photochemically produced oxidants generally exceeds that of photochemically produced reductants. The oxidizing power of rainwater is therefore greater than that due to dissolved molecular O2alone. The difference is small at present but becomes important at O2levels less than 10−3PAL. At O2levels between 10−4and 10−5PAL the oxidizing power of rainwater is almost independent ofpO2. Precambrian soils in which a part or all of the Fe2+in their source rocks has been oxidized to Fe3+could therefore have developed in the presence of an atmosphere with very low values ofpO2. On the other hand, the upper limit forpO2during early and mid‐Precambrian time suggested by the incomplete oxidation of FeO in soils developed on basaltic rocks is affected only slightly by the presence of photochemical prod

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10497

年代:1985

数据来源: WILEY

摘要:

From May 1959 to June 1981 the concentration of atmospheric carbon dioxide was measured in 2419 samples of air collected on a weather ship situated at 50°N and 145°W in the North Pacific Ocean. Three principal characteristics of the variation in concentration of atmospheric CO2are revealed by these data: an annual variation that repeats with nearly the same pattern each year, an interannual variation that correlates with the large‐scale circulation of the atmosphere, and a long‐term increase that is nearly proportional to the global input of CO2from the combustion of fossil fuels. The peak‐to‐trough amplitude of the smoothed annual signal increased from 13.3 ppm in 1969 to 14.5 ppm in 1981. The phasing of the annual CO2cycle suggests a close relation to the activity of land plants in the broad region of the northern hemisphere where plants grow mainly during the summer. The increasing amplitude suggests a heightening plant activity. The interannual variation and its first derivative correlate with the Southern Oscillation. A lag of 6 months in the derivative suggests a distant oceanic or terrestrial source‐sink in the tropics or southern hemisphere. The seasonally adjusted CO2concentration increased from 324.9 ppm in May 1969 to 340.8 ppm in June 1981. This increase is 60% of the increase that would have occurred if all the CO2from fossil fuel combustion had remained in the atmosphere and had been uniformly distributed there. The seasonally adjusted concentration, when averaged from 1975 to 1981, is 0.8 ppm lower than that found at Point Barrow, Alaska, at 71°N and 0.9 ppm higher than that found at Mauna Loa Observatory, Hawaii, at 19°N, suggesting a steadily decreasing concentration in CO2from north to south in the broad band from

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10511

年代:1985

数据来源: WILEY

摘要:

The concentration of atmospheric carbon dioxide at Mauna Loa Observatory exhibits a seasonal pattern that repeats with striking regularity from year to year. The amplitude of this seasonal signal, expressed either by peak‐to‐peak changes in concentration or as a series of harmonic terms, increased at an average rate of about 0.7% per year from 1958 to 1982. The estimated standard error in the linear coefficient of increase is 0.09%. Thus the increase appears to be highly significant statistically. A detailed examination of methods of calibration and of data analysis during this long record do not reveal any inconsistencies large enough to be responsible for the increase. Because the seasonal cycle of CO2in the northern hemisphere is thought to be due principally to the metabolic activity of terrestrial vegetation, it is likely that at least part of the increase is a result of increasing plant activ

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10529

年代:1985

数据来源: WILEY

摘要:

A new interpolation algorithm is derived for obtaining CO215‐μm transmissivities at any pressure from tables of transmission functions at standard pressures. The new method is a revision of the Fels‐Schwarzkopf (1981) technique. Improvements to the standard transmissivity tables are also discussed. An extension of these methods to calculate transmissivities at CO2concentrations other than those used for the tables is descr

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10541

年代:1985

数据来源: WILEY

摘要:

In order to develop the remote sensing techniques to infer cloud physical parameters, a multispectral cloud radiometer (MCR) was mounted on a NASA high‐altitude aircraft in conjunction with the Cooperative Convective Precipitation Experiment in 1981. The MCR has seven spectral channels, of which three are centered near windows associated with water vapor bands in the near infrared, two are centered near the oxygenAband at 0.76 μm, one is centered at the 1.14‐μm water vapor band, and one is centered in the thermal infrared. The reflectance and temperature measured on May 31, 1981, are presented together with theoretical calculations. The results indicate that the MCR produces quality measurements. Therefore several cloud parameters can be derived with good accuracy. The parameters are the cloud scaled optical thickness, cloud top pressure, volume scattering coefficient, particle thermodynamic phase, effective mean particle size, and cloud top temper

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10551

年代:1985

数据来源: WILEY

摘要:

GCM‐dependent, radiatively constrained cloud amount fields could be preferrable to currently available observed fields for calculating radiative fluxes in GCM's used in long‐range weather forecast studies. Motivated by this premise, we formulate an economical effective cloud algorithm for GCM's called “SATCLD,” which utilizes compact, readily accessible analyses of observed satellite‐derived radiative flux data. We then examine the plausibility of preliminary effective cloud fields. Analysis of SATCLD and other cloud fields and associated radiative fluxes (diagnosed by our GCM's cloud radiation model from observed atmospheric temperature and water vapor data) also provides some insight into biases in our GCM's cloud radiation model and surface albedo field. “SATCLD” generates effective low and high cloud amounts at each GCM grid point by minimizing the sum of the squares of the local residual (i.e., model‐diagnosed minus observed) shortwave and longwave radiative fluxes. The preliminary SATCLD effective cloud amount fields seem plausible in many respects, based upon comparison with the satellite‐derived 3DNEPH and surface‐based SFCOBS analyses. In the tropics the SATCLD effective high cloud amount is rather well correlated with 3DNEPH, while systematic differences in low cloud amount are evident in July. Off the west coasts of Central and South America and southern Africa, the SATCLD effective low cloud resembles SFCOBS in July. At mid‐latitudes the strongest similarities are between SATCLD versus 3DNEPH high cloud amount in July and SATCLD versus SFCOBS low cloud amount over the oceans. The SATCLD analysis is ill conditioned in the polar night region. Limitations of the present scheme as well as deficiencies in our GCM's cloud‐radiation model and surface albedo fields and in the archived satellite data are discussed. Suggestions are made for reducing discrepancies between effective versus real clouds without sacrificing consistency between GCM‐diagnosed versus

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10563

年代:1985

数据来源: WILEY

摘要:

Concentrations of aerosol NO3−and non‐sea‐salt (nss) SO4=have been measured in samples collected weekly between January 1981 and March 1982 at seven stations in the Sea‐Air Exchange Program Asian Dust Network in the North Pacific between 4°N and 53°N. Mean NO3−concentrations were relatively uniform, ranging between 0.18 and 0.35 μg/m3STP; mean nss SO4=ranged from 0.37 to 1.20 μg/m3STP. At most stations there was no consistent correlation between NO3−and nss SO4=or between these species and mineral aerosol. At Midway these species did covary in a clear and consistent manner; this correlation appears to be forced by large‐scale meteorological factors. In some cases, high nss SO4=concentrations were associated with high mineral aerosol concentrations; this suggests that the SO4=in these episodes was transported from the continents. A particularly impressive event occurred in May 1981, when much of the North Pacific region was affected by extremely high nss SO4=concentrations; evidence suggests that the SO4=was not derived from the soil material itself. At Fanning Island, NO3−concentrations showed a strong seasonal variation; there is evidence that the high NO3−concentrations are attributable to transport from the continents. In contrast, nss SO4=concentrations at Fanning were relatively constant throughout the year, and they were consistent with recent estimates of the oceanic emission rates of sulfur as dimethyl sulfide. The NO3−data from the tropics suggest that there is a relatively uniform background concentration of about 0.10 μg/m3STP; this concentration is close to that recently predicted by models that assume only lightning and the stratos

ISSN:0148-0227    

DOI:10.1029/JD090iD06p10586

年代:1985

数据来源: WILEY