摘要:

We have developed a three‐dimensional Eulerian regional acid deposition model to calculate episodic chemical concentrations and dry and wet deposition of acids in North America. This transport, transformation, and deposition modeling system subdivides the troposphere over the eastern United States, southeastern Canada, and the western Atlantic Ocean into a six‐level, 30 by 30 horizontal grid with a horizontal grid size of 80 × 80 km2. Transport and vertical diffusion of 24 trace gases and particles are calculated using temporally and spatially varying meteorology, provided by a mesoscale meteorological model. A gas phase chemical reaction mechanism is used to simulate concentrations and chemical conversion rates for 36 species, including 14 stable organics and 11 short‐lived radicals. Altitude‐, latitude‐, and season‐dependent photolysis rates for nine reactions in the chemical mechanism are specified using a delta‐Eddington radiative transfer model which includes O2and O3absorption, scattering and absorption by clouds and aerosols, Rayleigh scattering, and ground reflections. Subgrid scale vertical transport, aqueous chemical conversions, and trace gas and particle scavenging by clouds are parameterized using a one‐dimensional dynamical and microphysical cloud model and a box aqueous chemistry and scavenging submodel. The aqueous phase chemistry model includes sulfur oxidation by H2O2, O3, trace metals, and two organic peroxides, with numerous equilibria between all soluble trace species. Dry deposition rates for 13 compounds are computed using species‐specific deposition velocities that depend on the local meteorology, season, land type, insolation, and surface wetness conditions. Emissions of SO2, SO4=, NO, NO2, CO, NH3, and 10 classes of volatile organic compounds are included in the model. Trace gases are emitted into different vertical levels of the model according to a plume rise submodel. Hourly emissions are adjusted according to season and weekday or weekend activities. This model provides a framework to examine the relative importance and sensitivity of numerous physical and chemical processes responsible for the formation and deposition of tr

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14681

年代:1987

数据来源: WILEY

摘要:

Airborne measurements of trace gases and particles in the smoke from a prescribed burn of forest products in the Los Angeles basin show significantly higher emissions of NOx, SO2, and paniculate NO−3than do measurements in smokes from the burning of biomass in rural areas. It is postulated that the high emissions are due to the revolatilization of previously deposited pollutants. Implications for pollutant source inventories and the nuclear winter hypothesis are briefly discusse

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14701

年代:1987

数据来源: WILEY

摘要:

At a site near Boulder, Colorado, simultaneous atmospheric measurements were made of NO, NOx, and NOyin a field intercomparison of instruments involving two currently employed techniques of NOxand NOymeasurement. Both NOyinstruments depended upon the reduction of the NOyspecies to NO with detection by chemiluminescence, but different catalysts were employed for the reduction: (1) a gold catalyst (with addition of 0.3% CO) at 300°C, or (2) a molybdenum catalyst at 400°C. The two systems of NOxdetection involved (1) photolysis of NO2, and (2) reduction of NO2by solid ferrous sulfate. Several times during the intercomparison the response to calibrated samples of reference compounds NO, NO2, PAN, HNO3,n‐propyl nitrate (NPN), and NH3was measured. From the results the following conclusions were made: (1) The two NO instruments agreed on NO mixing ratios that were measured during the daytime hours over a range from the limits of detection to 35 parts per billion by volume (ppbv), (2) the two NOyinstruments gave similar estimates of NOyin ambient air over a wide range of mixing ratios (0.4–10 ppbv), and (3) the ferrous sulfate converter used for NOxdetection showed a significant interference from NPN an

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14710

年代:1987

数据来源: WILEY

摘要:

Precipitation was collected for a 1‐year period in Miami, Florida. The deposition rate of Al in samples containing Saharan dust was 10.1 μg/cm2, this flux is equivalent to a mineral deposition rate of 126 μg/cm2per year, a value comparable to the mineral accumulation rate in sediments of the tropical North Atlantic. Mineral deposition rates in rain were highly variable, with 22% of the total occurring in 1 day and 68% occurring in 4 days in two separate dust episodes. The volume‐weighted average concentration of dissolved Al in dust‐related rain events was 9.8 μg/L; if normalized to the total volume of rain that fell that year, the average would have a minimum value of 3.0 μg/L. The dissolved Al fraction (defined as all Al that passes through a 0.45‐μm filter) ranged from 0.5 to 48%, with a volume‐weighted mean of 5%; solubility tended to increase with decreasing rain pH and decreasing mineral concentration. If the 5% solubility applies to all Saharan dust deposited in the tropical Atlantic, then the annual deposition rate of soluble Al in this region would be 2–8×1011g, a rate commensurate with that carried by the Amazon; on a global basis the annual input to the oceans of soluble Al in dust would be 20–40×1011g, a rate comparable to that carried by rivers. These atmospheric input rates of dissolved Al are sufficient to account for many of the distribution features

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14723

年代:1987

数据来源: WILEY

摘要:

Carbon disulfide (CS2) was determined in surface water and the overlying atmosphere during three cruises covering the coastal areas of the eastern United States, the temperate North Atlantic, and the Sargasso Sea (April/May, August, September 1986: 25°–44°N and 66°–81°W). The CS2concentrations in surface waters were within the range of 2.5–510 pmol S(CS2) L−1(picomol CS2‐sulfur per liter). The mean concentrations in open ocean waters and coastal waters were 16 ± 8 (n= 95) and 33 ± 19 pmol S(CS2) L−1(n= 110), respectively. Comparison of the CS2concentrations measured in April/May and in September suggests the possibility of seasonal variability in the production of CS2in surface waters. The distribution patterns of CS2in the atmospheric boundary layer were similar to those observed in surface waters, with higher concentrations near the coast and lower levels over the open ocean. The typical background mixing ratio of CS2in the remote marine boundary layer is of the order of a few parts per trillion by volume. On the basis of our measurements of CS2in surface seawater and the overlying atmosphere, the global sea‐to‐air CS2flux is estimated to be 6.8 (3.4–14) Gmol S(CS2) yr−1, equivalent to 0

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14733

年代:1987

数据来源: WILEY

摘要:

The cycles of the water isotopic species (HDO and H218O) have been incorporated into the NASA Goddard Institute for Space Studies (GISS) atmospheric general circulation model (GCM). The results of a 3‐year simulation for present‐day conditions are discussed, with special emphasis on the comparison between predicted and observed isotopic distributions (well documented mainly through the International Atomic Energy Agency/World Meteorological Organization network) for both the seasonal and annual time scales. The observed seasonal cycles are generally well simulated. For the annual scale the observed linear relationship between δ18O and the surface temperature at middle and high latitudes, as well as the absence of any correlation between these fields in tropical and equatorial regions, are properly obeyed by the GCM simulation. In the tropical and equatorial regions the δ18O patterns for both observations and the GCM are influenced by the amount of rainfall. There is excellent agreement between the simulated and observed δD–δ18O relationship throughout

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14739

年代:1987

数据来源: WILEY

摘要:

Stratospheric aerosols collected over the western United States from late 1982 to early 1984 show the strong effects of El Chichón's eruption. Although mineral particles disappeared during this period, large (>0.9‐μm diameter) acid droplets were still common. Because these have never been seen in prevolcanic, background‐level collections, they apparently result from increased droplet growth made possible by the unusual abundance of sulfate. Aerosol size distributions show a wide variety of multimodal curves due to mixing of air masses containing aerosols of various ages or histories. Toward the end of the study time there are fewer large aerosols because of gravitational settling and poleward transport. The result is a steady reduction in sulfate, as most aerosol mass is concentrated in a small number of large droplets. Even the later sulfate levels (0.3 μg m−3) are, however, 5 times typical prevolcanic background contents (about 0.06 μg m−3). Thus the influence of El Chichón on high‐altitude (15–21 km) air was still considerable 22 month

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14761

年代:1987

数据来源: WILEY

摘要:

A quantitative search for a theoretically predicted CO2signal in surface air temperature data extending back to 1899 was marginally successful in a statistical sense. However, the nature of the signal strength time series suggested that this result is an artifact of large‐scale decadal variations at the beginning and end of the record. Application of the “fingerprint” strategy to three different global fields of climate variables over the last 25–35 years showed no significant CO2signal. The analysis pointed up the need to use: (1) model signal‐to‐noise ratios in selecting fields for subsequent analysis and (2) multiple fields in the detection process. Most importantly, we found the primary pattern of natural air temperature variability to be very similar to the expected CO2signal, thus suggesting that the air temperature field is not the best place to attempt early detection of the CO2signal. By contrast, the primary pattern of natural variability and the expected CO2signal in the ocean's surface temperature are substantially different; this suggests the oceans as a low‐noise environment in which to attempt ea

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14772

年代:1987

数据来源: WILEY

摘要:

Two classes of variability in stratospheric trace species: (1) dynamically introduced tracer irregularities and (2) diurnal variations in photochemically active species, are investigated with regard to asynoptic satellite measurements. The fidelity with which the continuous synoptic behavior may be derived from discrete asynoptic measurements is explored. For both classes of variability several diagnostics of the continuous behavior (e.g., space‐time spectra, synoptic maps, time‐mean fields) are constructed from asynoptic measurements and compared with the true variability. Irregular tracer behavior of dynamical origin, as may follow large amplitude wave events or stratospheric warmings, is treated in a stochastic framework. An advected space‐time process is constructed according to prescribed correlation scales, reflecting the spatial extent and lifetime of tracer anomalies which are introduced randomly into the field and advected about the globe in a specified zonal flow. In the case of diurnal variations, e.g., in photochemically active gases in the upper stratosphere and mesosphere, a solar waveform is prescribed to propagate through a latitudinal envelope. The structure of this solar signature is truncated to the sunlit side of the globe to mimic the response of photochemically active species. For both classes of variability (under plausible scales and advection speeds in the case of random tracer fluctuations) the continuous synoptic behavior is corrupted by aliasing from variance unresolved by asynoptic sampling. While some of this contamination may be eliminated by correctly assimilating combined (ascending plus descending) data, the behavior interpolated to synoptic times can be pathological. For random tracer variability the time‐mean field, at least, can be correctly retrieved even if the behavior is undersampled, owing to cancellation of aliases in the averaging process. However, time‐mean distributions of photochemically active species may not be faithfully captured, because diurnal fluctuations alias to the time‐mean, and this aliasing is not eliminated by averaging over time. With the availability of contemporaneous measurements from several instruments viewing different regions of the globe (e.g., the Upper Atmosphere Research Satellite (UARS)), it may be possible to alleviate these difficulties, rooted in sampling deficiencies, by capitalizing on the extended information content of the combined data. The success of such a procedure will hinge on explicitly accounting for sampling irregularities inherent to the collective da

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14781

年代:1987

数据来源: WILEY

摘要:

ClONO2was observed in high‐resolution infrared emission spectra obtained on November 6, 1984, by a balloon‐borne Fourier spectrometer. The observations took place near 0300 LT at a latitude of 35°N. Spectral simulations are used to determine the mixing ratios of ClONO2. This analysis incorporates line by line calculations and new ClONO2cross sections measured in the laboratory at 223 K. The inferred mixing ratios of ClONO2are 1.3±0.45 ppb and 0.98±0.35 ppb at 14 and 34 mbar. One‐dimensional photochemical model predictions are compared to the observations. The ClONO2mixing ratio at 34 mbar appears to be larger than theory, while there is agreement at

ISSN:0148-0227    

DOI:10.1029/JD092iD12p14806

年代:1987

数据来源: WILEY