摘要:

We reeaxmine the “nuclear winter” hypothesis with a three‐dimensional global model modified to allow for localized injection of smoke, its transport by the simulated winds, its absorption of sunlight, and its removal by model‐simulated precipitation. Smoke injected into the troposphere is driven upward by solar heating. The tropopause, initially above the smoke, reforms below the heated smoke layer and separates it from precipitation below. Although much smoke is scavenged while the thermal structure is being altered, the residence time of the remaining smoke is greatly increased. We find, particularly for July conditions, a longer‐lasting “nuclear winter” effect than was found in earlier modeling studies in which normal tropospheric residence times were assumed. In January the smaller solar flux in the northern hemisphere allows faster removal of smoke than in July. Significant cooling of the northern hemisphere continents is predicted; its dependence on season and injected smoke mass

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01039

年代:1986

数据来源: WILEY

摘要:

A major outbreak of Saharan dust (>40 μg aerosols/m3air) passed over the western Sargasso Sea in late June 1980. The flux of aeolian particles across the air‐sea interface was calculated based upon free‐floating sediment trap data (30‐m depth). During the early‐to‐middle portions of this event, we observed in the trap samples large numbers of “giant” (>20‐μm diameter) aeolian particles that were not observed in aerosol samples collected at Miami, Florida, 426 km to the west. To better intercompare data collected at the two sites, a simple aeolian particle settling model was developed. Scanning electron microscopy with automated image analysis and X ray energy spectroscopy of individual particles from the two sites provided size and compositional data as primary inputs to the model. The compositional differences between aerosols from the two sites, although not great, may have been due in part to the localized nature of particle sources and storm centers. The time history of the aerosol concentration over the western Sargasso during the month of June as simulated by the model was compared with the time history of aerosols arriving at Miami. These results suggest that a significant portion of the deposition flux is comprised of giant particles. Particles in this size range are not efficiently collected by conventional sampling techniques, and hence reported estimates of depositional fluxes could be significant

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01055

年代:1986

数据来源: WILEY

摘要:

Seasonal estimates of sea‐salt aerosol particle concentration distributions 15 m above the sea are presented on global contour maps. Measured data from a variety of sources relating atmospheric sea‐salt concentration to wind speed have been combined, yielding relationships of formC= exp (as+b), whereCis sea‐salt concentration in micrograms per cubic meter andsis the horizontal wind speed in meters per second. These relationships, coupled with a Gaussian wind speed frequency distribution, allow us to calculate the atmospheric sea‐salt concentration accounting for the variance about mean wind speeds. We use monthly wind mean speed and variance information in 5° × 5° latitude/longitude squares over the world ocean to estimate the global sea‐salt aerosol particle mass distribution. The atmospheric sea‐salt concentrations in the northern hemisphere marine troposphere display a substantial seasonal dependence. The 3‐month seasonal average sea‐salt concentrations in this region differ by a factor of 2–3 between the boreal winter and summer, and the highest values are between 40 and 49 μg m−3. The seasonal variability of atmospheric sea‐salt concentrations in the high‐latitude southern hemisphere is much less than that in the northern hemisphere, varying by less than a factor of 2 between the austral winter and summer, and again the highest values are about 45 μg m−3. The equatorial areas have uniformly lower atmospheric sea‐salt concentrations than the high‐latitude regions. The monsoonal winds over the Indian Ocean produce sea‐salt concentrations in excess of 40 μg m

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01067

年代:1986

数据来源: WILEY

摘要:

A systematic characterization of the atmospheric H2SO4‐HNO3‐NH3system was conducted in the fog water, the aerosol, and the gas phase at a network of sites in the San Joaquin Valley of California. Spatial patterns of concentrations were established that reflect the distribution of SO2, NOx, and NH3emissions within the valley. The concept of atmospheric alkalinity was introduced to interpret these concentrations in terms of the buffering capacity of the atmosphere with respect to inputs of strong acids. Regions of predominantly acidic and alkaline fog water were identified. Fog water was found to be alkaline in most of the valley, but small changes in emission budgets could lead to widespread acid fog. An extended stagnation episode was studied in detail: progressive accumulation of H2SO4‐HNO3‐NH3species was documented over the course of the episode and interpreted in terms of production and removal mechanisms. Secondary production of strong acids H2SO4and HNO3under stagnant conditions resulted in a complete titration of available alkalinity at the sites farthest from NH3sources. A steady SO2conversion rate of 0.4–1.1% h−1was estimated in the stagnant mixed layer under overcast conditions and was attributed to nonphotochemical heterogeneous processes. Removal of SO2was enhanced in fog, compared to nonfoggy conditions. Conversion of NOxto HNO3slowed down during the stagnation episode because of reduced photochemical activity; fog did not appear to enhance conversion of NOx. Decreases in total HNO3concentrations were observed upon acidification of the atmosphere and were attributed to displacement of NO3−by H2SO4in the aerosol, followed by rapid deposition of HNO3(g). The occurrence of fog was associated with general decreases of aerosol concentrations due to enhanced removal

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01073

年代:1986

数据来源: WILEY

摘要:

Concentrations of HNO3(g) and NH3(g) determined in the field were compared to predictions from aerosol equilibrium models. The products of HNO3(g) and NH3(g) concentrations measured under cool and humid nonfoggy conditions agreed in magnitude with predictions from a comprehensive thermodynamic model for the atmospheric H2SO4‐HNO3‐NH3‐H2O system. Observed concentrations of NH3(g) in fogs were generally consistent with those predicted at equilibrium with fog water, but important discrepancies were noted in some cases. These discrepancies may be due to fluctuations in fog water composition over the course of sample collection or to the sampling of nonfoggy pockets of air present within the fog. Detectable concentrations of HNO3(g) (up to 23 neq m−3) were often found in fogs withpH5 were below the detection limit of 4–

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01089

年代:1986

数据来源: WILEY

摘要:

During November and December of 1981, surface‐layer eddy fluxes of small atmospheric ions were measured at the Amundsen‐Scott South Pole Station. This was done in the electrode layer at a height of 2.5 m by means of the eddy correlation method. The mean eddy fluxes of positive and negative ions were found to be approximately 40 and 440 cm−2s−1respectively, and the fluxes were always found to be toward the ground. The large difference between the two is attributed to the electrode effect, which is responsible for a large gradient in the negative ion concen

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01097

年代:1986

数据来源: WILEY

摘要:

Stratospheric constituents are determined by continuity equations including photochemical production and loss as well as the transport and diffusion terms and explicit time variation. Photochemical models self‐consistently solve these equations to determine species concentrations. Recent Nimbus 7 measurements give us a first chance to analyze diagnostically the global atmosphere for consistency. We compute the diurnal average photochemical production and loss terms of ozone using monthly and zonally averaged limb infrared monitor of the stratosphere (LIMS) O3, H2O, HNO3, NO2, and temperature and stratospheric and mesospheric sounder (SAMS) CH4data. The loss rates of ozone by pure oxygen species, by the nitrogen oxides, and by the hydrogen oxides are calculated along with the production rate of ozone by oxygen photolysis. The other major loss rate for ozone, which is the loss rate by the chlorine family, is calculated from a two‐dimensional model including SAMS CH4measurements and a total Clxof 3 ppbv at the stratopause, yielding a ClO profile in good agreement with balloon measurements. All loss rates of ozone are therefore tied to experimental measurements. Ozone is thought to be in photochemical equilibrium at low latitudes near 2 mbar; however, our calculations show the diurnal average ozone loss to be about 40–60% higher than the production. Therefore photochemical models using LIMS H2O, HNO3, NO2, and temperature and SAMS CH4will predict lower ozone concentrations than those measured by LIMS. Uncertainties in this region are a factor of 1.7 with the major contributions coming from the O3measurements, the calculated photolysis of O3to O(1D), and the calculated photolysis f

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01103

年代:1986

数据来源: WILEY

摘要:

Zonally averaged limb infrared monitor of the stratosphere data from the Nimbus 7 satellite are used together with an essentially algebraic photochemical equilibrium model to infer concentrations of Ox, HOx, and NOxspecies over most of the stratosphere for the period from March 26, 1979 to April 1, 1979. Since the model is algebraic, sensitivity coefficients (logarithmic partial derivatives of inferred concentrations with respect to model input) may also be calculated. These are combined with estimates of the uncertainty in the model input parameters (concentrations, rate constants, photolysis rates) to give uncertainty factors for the inferred concentrations. Concentrations of OH and HO2are calculated and found to compare reasonably well with previous measurements and two‐dimensional model calculations. Uncertainties are found, in general, to be largest in the lower stratosphere and to be greater for HO2than they are for OH. The method of inference of OH concentration is found to have a great effect on the uncertainty factors calculated for HO

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01117

年代:1986

数据来源: WILEY

摘要:

Monthly, zonally averaged limb infrared monitor of the stratosphere data from the Nimbus 7 satellite are used with an essentially algebraic photochemical equilibrium model presented in part 1 of this series (Kaye and Jackman, this issue) to infer concentrations and uncertainties of the odd hydrogen species OH, HO2, H2O2, and HO2NO2as a function of altitude, latitude, and season. The inferred concentrations for OH and H2O2are found to be reasonably consistent with some but not all previous observations; most of the inferred HO2concentrations are below those which have been observed. Concentrations of all inferred species at mid‐latitudes are expected to maximize in the summer. Uncertaintiesuiare found to be largest in the lower stratosphere for all species and to decrease approximately in the orderuH2O2>uHO2NO2>uHO2>uOHover most of the stratosphere. In the tropics and at mid‐latitudes the variation of the uncertainties with latitude and season is substantially smaller than the inferred variation of the concentrati

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01137

年代:1986

数据来源: WILEY

摘要:

The consistency of contemporary stratospheric ozone photochemistry is examined in the light of recent data from the Nimbus 7 satellite. Temperature, O3, H2O, HNO3, and NO2data from the limb infrared monitor of the stratosphere experiment and CH4from the stratospheric and mesospheric sounder experiment are used in conjunction with a simplified photochemical model to compare calculated and observed O3for 30°N during March. The photochemical model underestimates the ozone in the upper stratosphere by 15–32%. Calculated and observed mixing ratios of NO2and OH and the daytime value of the ratio HNO3/NO2are presented. Results from a Monte Carlo analysis of the uncertainty due to errors in the input data are also given. The sensitivity of the model results to modification of certain key reaction rate constants is studied. These changes result in higher ozone mixing ratios in the upper stratosphere, which are in better agreement with the data. The effect of such modifications on other photochemical parameters is shown. The level of agreement between theory and observations with regard to the temperature sensitivity of O3and the diurnal variations in O3is discuss

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01153

年代:1986

数据来源: WILEY