摘要:

Latitudinal distributions of ethane, propane, propene, and acetylene in air over the Atlantic from 48°N to 4°S are reported. In addition, measurements of saturated and unsaturated hydrocarbons (C2–C5) at low latitudes and from 55°N to 80°N are presented. The mixing ratios of ethane, propane, and acetylene were found to vary systematically between a few tenths of a ppb and a few ppb. The alkene and higher alkane (C4and C5) mixing ratios were found to be in the ppt range. The data are discussed with respect to the source distributions and atmospheric lifetimes of the different hydroca

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11959

年代:1981

数据来源: WILEY

摘要:

Nighttime concentration profiles of the nitrate radical (NO3) together with NO2and O3were observed spectroscopically. Kinetic analysis of the NO3formation, the early morning photolysis of NO3, and stoichiometric considerations allowed three independent estimates of the equilibrium constantKeq= [NO3] · [NO2]/[N2O5]. From those observations an averageKeqof (2.0±l) × 1010cm−3(at 10°C) is derived. Maximum concentrations of NO3were found to be highly variable. Lifetimes for NO3shorter than l min in the presence of fog indicate a fast reaction of N2O5with liquid water droplets. At relative humidities below 50% the maximum NO3concentrations were still lower than expected from the NOx–O3reaction sequences which must be due to unknown sinks for NO3and/or N2O5or to an inadequacy in the presently accepted reaction

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11965

年代:1981

数据来源: WILEY

摘要:

The rate of uptake of NO2by liquid water according to (R1), 2NO2(g) + H2O(1) → 2H++ NO3−+ NO2−, is shown to be unaffected by O2(0.2 atm). Hence the rate constant and Henry's law solubility constant of NO2previously obtained may be employed to evaluate the rates of aqueous phase reactions of NO2in the ambient atmosphere. Reactions (R1) and (R2), NO2(g) + NO(g) + H2O(1) → 2H++ 2NO2−, are quite slow at representative atmospheric partial pressures and cloud liquid water content; the characteristic times range upward from 103–104hours at 10−7atm, increasing with decreasing partial pressures of the gases. Direct acidification of cloud liquid water by (R1) or (R2) is also unimportant. Catalytic enhancement of (R1) is potentially important for catalyst concentrations of order 10−7M, assuming sufficiently fast rate constants (∼108M−ls−1). Iron‐catalyzed reaction in particular, however, is found to be unimportant. Reaction of NO2with dissolved S(IV) is potentially mportant, based upon an assumed upper limit rate constant of 2.5×107M−1s−1. Deposition of NO2to surface (ocean or lake) water is shown to be controlled by aqueous phase mass transport and/or reaction and is much sl

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11971

年代:1981

数据来源: WILEY

摘要:

We present the results of an experimental investigation of the ultraviolet photolysis of mixtures of phosphine in hydrogen. Under no circumstances could red phosphorus be produced in this system. Rather, the product was always yellow. The measured indices of refraction of the phosphorus produced were used to fit the variation of reflectivity of Jupiter's Great Red Spot with wavelength. It was found that the phosphorus particles have to be small (0.05 μm) and their layer should have an optical depth of about one at λ=0.4

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11985

年代:1981

数据来源: WILEY

摘要:

A parameterization of two‐dimensional transport is developed for application to photochemical models of stratospheric trace species. It is shown that in a first approximation tracer transport in the meridional plane may be treated as an advective, rather than a diffusive, process. The mean meridional motion used in this advective model is a modified Eulerian mean which is a good approximation to the Lagrangian mean motion. The potential of the proposed parameterization is demonstrated by a simple numerical experiment in which the equilibrium distribution is computed for a tracer with a uniform tropospheric source and a stratospheric sink proportional to the local mixing ratio. The resulting distribution is qualitatively in accord with the oberved stratospheric distribution of trace species whose sources are in the troposphere, e.g., N2

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11989

年代:1981

数据来源: WILEY

摘要:

This study is an attempt to estimate the effect of a geographical distribution of clouds on climate. A method of determination of a three‐dimensional cloud distribution is proposed. It is based on the solution of the inverse problem for the radiative transfer equation. By using climatic data on total cloud amount, temperature, mixing ratio of water vapor, and satellite data on outgoing longwave radiation, the global distributions of high, middle, and low clouds were computed for July. The derived vertical cloud extension is in fair agreement with available data on the frequency distribution of stratiform and cumulus clouds. Two numerical experiments are carried out with an atmospheric general circulation model in which zonal and geographical cloud distributions are prescribed. The integrations are performed for 60 days with a GFDL model, and the last 30 days are analyzed. The geographical cloud distribution causes the increase of surface temperature over the continents by 2°–4° and leads to a decrease of surface pressure there and an increase over the oceans. The largest changes in the surface pressure, up to ±12 mbar, occur in the middle latitudes of both hemispheres. The largest differences in precipitation are observed in the tropics and over some coastal regions of North and South America. Arid areas in the subtropical belt become more pronounced in case of the geographical distribution of clouds. Estimates of the level of significance for precipitation and surface pressure changes reveal that they are statistically significant in some areas of the

ISSN:0148-0227    

DOI:10.1029/JC086iC12p11995

年代:1981

数据来源: WILEY

摘要:

By using a hemispheric thermodynamic grid model, the annual cycle of climate for 18,000 years ago is simulated. It is shown that the difference between the position of the snow‐ice boundary of 18,000 years ago and the one of today was much larger in summer than in winter and that the annual cycle of the snow‐ice boundary for today has more variability than that for 18,000 years ago. Owing to the temperature snow‐ice feedback, the zonally averaged ground and midtropospheric temperature anomalies (with respect to today normals) are negative and their absolute values are larger in summer than for the other seasons of the year and increase from lower to higher latitudes. In lower latitudes, in some regions of Asia and Africa, the spring and early summer temperatures were higher during the ice age climate because the insolation was about 20 W m−2higher than it is today, and the lower latitudes are much more sensitive to insolation than the higher latitudes are, where the temperature snow‐ice feedback is the main mechanism which produced a dominant decrease of temperature. Comparison of the computed surface temperature values with the ‘Observed’ values shows generally good agreement. The computed average ground temperature anomaly for the northern hemisphere for July is equal to −4.7°C, in good agreement with the values −4.8°

ISSN:0148-0227    

DOI:10.1029/JC086iC12p12015

年代:1981

数据来源: WILEY

摘要:

Considerable attention is being focused on the possible climatic effects resulting from increases in the concentration of atmospheric carbon dioxide. In calculating CO2influence on the thermal structure of the atmosphere, the role of clouds is critically important. Not only are the cloud properties, such as amount, numbers of clouds, altitudes, and optical properties important but also whether or not these properties are fixed or coupled to model temperatures. The transport of water vapor determines whether or not a region has clouds, the cloud properites, and the water vapor profiles appropriate for clear and cloudy skies. Results are presented of the change in surface temperature with changes in carbon dioxide content for two radiative‐convective models with three different cloud coverages. We used (1) the Manabe‐Wetherald radiative‐convective model in which three clouds with fixed pressures, thicknesses, and optical properties and a single water vapor profile are inputed and (2) the Hummel‐Kuhn model, which couples radiative heating, convection, and water vapor transport in order to calculate locations and thicknesses. The Hummel‐Kuhn model yields temperature increases for doubled CO2larger than the Manabe‐Wetherald model for various assumed total cloud cover amounts. For assumed standard cloud cover amounts the Hummel‐Kuhn estimate is 20% larger than the Manabe‐Wetherald estimate. For reduced and enhanced cloud cover amounts the Hummel‐Kuhn estimates are 37% and 17% larger, respectively. The calculated cloud locations and thicknesses did not change in the calculations; therefore the increased sensitivity in the Hummel‐Kuhn model is due to the larger water vapor amounts in the Hummel‐Kuhn model and the added infrared absorption by

ISSN:0148-0227    

DOI:10.1029/JC086iC12p12035

年代:1981

数据来源: WILEY

摘要:

A two‐dimensional chemical model of the atmosphere is described. The model includes the major features associated with advanced one‐dimensional models: 30 active chemical species and all the important chemical reactions connecting them, diurnal effects, and Rayleigh scattering. The species are transported and calculated separately, with the exception of the odd oxygen family [O3, O(3P), O(1D)] and H and N atoms. The transport scheme contains both diffusive and advective terms, with the advective circulation field of Murgatroyd and Singleton (appropriately scaled) used to approximate the Lagrangian mean flow. Comparison of the model predictions with atmospheric observations of long‐lived trace species such as O3, N2O, CF2Cl2, CFCl3, and CH4suggests that the transport parameterization gives a good representation of actual trace species motions. For constituents which are more active or whose chemistry is less well known, the model is a useful diagnostic tool for assessing our current understanding of atmospheric chemistry. A number of significant discrepancies between experiment and theory are highlighted, the most important being in the Clxand NOyfam

ISSN:0148-0227    

DOI:10.1029/JC086iC12p12039

年代:1981

数据来源: WILEY

摘要:

A simulation of the altitude distributions of HNO3, NO2, and NO measured on the Stratoprobe balloon flight of August 28, 1976, has been carried out by using a time‐dependent stratospheric model with extensive photochemistry. The measured ozone and temperature profiles were employed in the simulation. The simulated ratios for HNO3/NO2and HNO3/NO are significantly larger than the measured ratios for HNO3/NO2and HNO3/NO in the altitude range 20–30 km. Since these ratios are proportional to the hydroxyl densities, it is proposed that the actual hydroxyl densities are a factor of 3–5 lower than calculated in the model, using current chemical rate data. By assigning a pressure dependence to the OH + HO2reaction rate as well as including the OH + HNO3reaction rate to reduce the OH densities in the model over this altitude range, an empirical simulation of the measured ratios was obtained. The pressure dependence chosen for the rate was such that reasonable agreement with existing measurements of hydroxyl densities at higher altitudes was still obt

ISSN:0148-0227    

DOI:10.1029/JC086iC12p12066

年代:1981

数据来源: WILEY