摘要:

Reactive surface emissions of reduced sulfur gases can produce SO2in the middle and upper troposphere at the levels of 80±30 pptv measured high over the remote oceans. We present simulations with a two‐dimensional “Staubsauger” or “vacuum cleaner” model that combines a photochemical model with a description of vertical transport of trace species by convective clouds within larger synoptic circulations. Emissions of 20–60 Tg (S)/yr of (CH3)2S, H2S, or CS2, may produce the observed SO2. Roughly equal production rates of SO2and methane sulfonic acid may be expected. The amount and exact vertical distribution of the SO2produced remain uncertain: the greatest chemical uncertainties are the reaction yield of SO2expectable under clean tropospheric conditions and also the liquid‐phase removal of SO2, and the oxidation rate. The amount of upper tropospheric SO2produced depends substantially on the proximity of strong reduced S sources to regions of active convection. However, the character of the solutions we present is invariably distinctly different from those obtained with one‐ or two‐dimensional models employing the eddy‐diffusion hypothesis. The results of the model point beyond its original conception, and stress the likely importance of the rainy tropical jungles and mid‐latitude industrial regions, since both regions have large sulfur emissions arid frequently active cumulonimbus convection. This process, however, should contribute mainly to upper‐tropospheric SO2. Other chemical implications are that tropospheric OH may depend critically on HOOH levels as well as the hydrocarbon and nitrogen oxide cycles. Cloud transport may play an important role in these cycles. The hydroxyl radical concentration depends as much on assumptions regarding HOOH reaction and transport

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07111

年代:1984

数据来源: WILEY

摘要:

A two‐dimensional kinematic model of warm‐frontal precipitation has been employed to model the sulfur chemistry of warm‐frontal rainbands. Analysis of the model results indicates that nucleation scavenging, in‐solution oxidation of SO2, and impaction of particulate sulfate by hydrometeors all contribute significantly to wet sulfate deposition, with nucleation scavenging generally the most important process. The model results also indicate that, in general, sulfate deposition will be a nonlinear function of the initial amount of sulfur species. Model predictions of sulfate concentrations in rain from warm‐frontal rainbands and the variability of these concentrations within individual rain events are in accord with obs

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07133

年代:1984

数据来源: WILEY

摘要:

Vertical profiles are reported for sulfate, for strong acid‐to‐sulfate molar ratios, and for related species. Data were obtained in the northeastern United States by airborne filter‐pack sampling at multiple altitudes with some concurrent ground measurements and by impactor measurements on the ground and aloft, using semiquantitative FTIR spectroscopic analyses. Filter‐pack and impactor approaches were compared during one experimental period. Vertical profile data demonstrate that acid‐to‐sulfate ratios in ambient aerosols usually increase with altitude (Z) in the lower troposphere, occasionally remain constant with Z, and almost never decrease with Z. The sum of nitrate and nitric acid decreases with Z, but the fraction as nitric acid increases with Z, consistent with the aerosol acidity data. Urban effects on the acid‐to‐sulfate ratios in aerosols are demonstrated. The results strongly suggest that reequilibration of the aerosol nitric acid‐ammonia system must be occurring rapidly and that strong acids (in aerosols and gases) may be available for long‐distance transport in th

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07149

年代:1984

数据来源: WILEY

摘要:

Radiation fog water samples collected at the Albany (NY) County airport show quite low acid content compared with previously published data on fog acidity: the pH ranges from 4.3 to 6.4. This fog water ionic concentration is indicative of low pollution in this area. The leading mechanism responsible for the variability in aqueous concentration of nonvolatile ionic constituents of these fogs is the growth and evaporation of droplets, as reflected by the variation of LWC during the fog evolution. For these reasons the origin and composition of aerosol on which fog droplet condensation takes place is of major importance. Droplet size spectra analysis show that there is a need for improving the collection methods of fog water in order to better describe the chemistry involved, especially to maximize the drop capture efficiency of the collectors and reduce the sampling time for better resolution.

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07159

年代:1984

数据来源: WILEY

摘要:

The coalescence efficiency for accretion was assumed to be governed by a collisional Weber number. This concept was used with the aid of theoretical collision efficiences to organize collection efficiency data from several sources into a unified set. The resulting collection efficiencies show a maximum of 71% for a collector drop of 115 μm and a cloud droplet of 12‐μm radius. Accretion calculations were made for a monodisperse cloud to illustrate the effects of cloud droplet sizes and collection efficiencies on drop growth. The time average collection efficiency for growth from 50 to 500 μm by accretion of 30‐μm droplets is reduced by 50% when compared to the time average collision efficiency. A maximum of 65% in the time average collection efficiency occurs for accretion of 10‐μm droplets. The contribution to accretion by cloud droplets smaller than 5 μm appears to be

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07165

年代:1984

数据来源: WILEY

摘要:

Microwave radiances have been computed as a function of rainfall rates from precipitating clouds containing ice, combined phase, and water hydrometeors. The ice at the top of the precipitating cloud depresses the brightness temperatures by reflecting radiances that emerge from the liquid hydrometeors at lower altitudes. Because the density of ice hydrometeors is related to the rainfall rate at the surface, the brightness temperatures are sensitive to large rainfall rates. The solution of the transfer equation considers the vertically inhomogeneous structure of the precipitation as well as the polarized emissivity of the underlying surface. The altitudes from which radiances derive their energy are presented for several rainfall profiles and frequencies. It is shown that the lower‐frequency radiances are sensitive to liquid precipitation at low altitudes while the higher‐frequency radiances are more sensitive to the ice hydrometeors at the cloud tops. The extinction coefficients of aspherical hydrometeors are presented as a function of rainfall rates. Measurements at 37.0‐GHz microwave radiances from Nimbus 7 suggest that the vertically polarized radiances are 12±2°K warmer than the horizontally polarized radiances at high rainfall rates. This difference diminishes at lower frequencies. The present model reveals that such effects can be traced to aspherical ice hydrometeors in the upper regions of precipitating

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07170

年代:1984

数据来源: WILEY

摘要:

The parameterization of solar reflection from clouds used in climate and general circulation models is based on radiative transfer theory appropriate for plane parallel clouds. We have attempted to relate the reflection from a broken cloud field to that from a plane parallel cloud of the same optical properties by using Monte Carlo simulations for a very simple model of an array of regularly spaced, infinitely long bar clouds. Reflection from the array is represented by an effective cloud fraction, and it is shown that for many cases this may be obtained by treating the cloud elements to be noninteracting azimuthally symmetric reflectors. The effective cloud fraction is a function of solar zenith angle, the aspect ratio of the individual cloud elements, and the normal or zenith cloud fraction of the array. Model computations for reflection from an array of randomly distributed identical cylinders are also presented as an example of a possible application of this technique.

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07179

年代:1984

数据来源: WILEY

摘要:

Using an exact multifrequency algorithm, relaxation rates for individual 15‐μ CO2lines have been calculated in the upper stratosphere and lower mesosphere for the Cira (1972) global mean reference atmosphere. The relaxation rate dependence on wave number is obtained and examined as a function of line strength and altitude, to clarify the underlying physics. Wave numbersn≲2.09 km−1are accurately treated by the algorithm. The most rapid growth of relaxation rate with wave number is τ−1∝n1.2, which occurs for strong, mostly Doppler‐broadened lines in the mesosphere. Overall relaxation rates for the CO215‐μ band complex are obtained from an approximate model of the line strength distribution; these rates corroborate previous results of Fels. Our results for individual lines, however, differ significantly from Fels' parameterization. Comparison of the present results with our previous rates obtained with the diffusion approximation demonstrates reasonably good agreement down to wavelengths of ∼8 km, below which this approximation seriously overestimates t

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07187

年代:1984

数据来源: WILEY

摘要:

A method of high‐resolution frequency analysis is applied to three geological time series. It is shown that the characteristic frequencies in these series are almost identical with some of the major characteristic frequencies of the earth's orbital elements and their linear combinations. The analysis supports the Milankovitch orbital theory of long‐term climatic chan

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07195

年代:1984

数据来源: WILEY

摘要:

The linear instability of forced stationary waves in a baroclinic zonal flow is examined with a two‐level quasi‐geostrophic beta plane model. Realistic zonal topography and diabatic forcings produce a steady state solution of planetary‐scale stationary waves. Baroclinic instability of the forced waves gives rise to transient perturbation modes of planetary zonal scale and a preferred meridional scale of about twice the radius of deformation. One of the dominant planetary modes is stationary and resembles the observed stationary wave pattern. In the steady state model this form can be obtained only for certain values of the meridional scale of the forcings. It is suggested that this stationary mode could contribute to the time average stationary wave distribution. Applications to blocking are also considered. Interference of stationary and quasi‐stationary modes can apparently produce regional as well as global blocking p

ISSN:0148-0227    

DOI:10.1029/JD089iD05p07202

年代:1984

数据来源: WILEY