摘要:

Measurements of NO, NO2, HNO3, particulate nitrate, peroxyacetyl nitrate (PAN), O3, and total reactive odd nitrogen (NOy) were made in the nonurban troposphere during the summer and fall of 1984. The field site was located near Niwot Ridge, Colorado, at an elevation of 3 km. NOywas measured by catalytic reduction to NO, followed by the detection of NO with a chemiluminescence instrument. The other species were measured with conventional techniques. The data and interpretation presented focus primarily on the relationships between a measurement of NOyand concurrent measurements of the individual species, as examined through ratio and correlation plots. Through the separate display of daytime and nighttime data, the plots provide insight into the photochemical nature of the individual species. In addition, the composition of NOyis addressed through a comparison of the measured NOylevel with that found for the sum of the measured component species. The NOylevel systematically exceeded the sum level, with the difference being larger in the summer than in the fall. The presence of organic nitrate species other than PAN is proposed as one way to account for the observed difference.

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09781

年代:1986

数据来源: WILEY

摘要:

A particle dry‐deposition parameterization scheme for use in tracer transport models is presented. The scheme produces particle deposition velocities relative to the bottom transport model level expressed in terms of wind speed, temperature, and air density at the bottom model level; surface momentum drag coefficient; particle size and density; characteristics of the surface roughness elements; and several parameters derived for different surface types. A two‐layer boundary layer model is employed to calculate the surface deposition velocities. Formulas for the particle deposition velocity are derived for four surface types: smooth surfaces, surfaces with bluff roughness elements, ocean surfaces, and vegetative canopies. The following processes are included in the model: turbulent transport through the boundary layer, gravitational settling, deposition by Brownian diffusion, interception and impaction on the surface roughness elements, diffusiophoresis on water surfaces, and, in limited cases, particle bounce‐off. Electrical and thermophoretic effects are ignored as well as particle blow‐off. As an illustrative example, the scheme is applied to a general circulation model to calculate the deposition velocities of ambient tropospheric aerosols. The calculated deposition velocities show a strong dependence upon the wind field in the bottom model level, the particle size distribution, and, to a lesser extent, the surface type. Particle mass deposition velocities of continental aerosols are found to lie in the range 0.003–0.036 cm/s for the accumulation mode and in the range 0.5–2.5 cm/s for the

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09794

年代:1986

数据来源: WILEY

摘要:

The chemistry of OH in a remote nonprecipitating tropical cloud is studied with a coupled gas‐phase and aqueous‐phase chemical model. The model takes into account the radial dependence of the concentrations of short‐lived aqueous‐phase species, in particular O3(aq) and OH(aq). The radical OH(aq) is produced rapidly by the aqueous‐phase reactions O2−+ O3and H2O2+hν and is removed primarily by oxidation of H2C(OH)2, H2O2, and HCOO−. Gas‐droplet transfer of OH must be modeled as a reversible process, that is, the droplets cannot be assumed to be diffusion‐limited OH(g) sinks. A strong OH(aq) concentration gradient exists between the surface and the interior of the droplets. The concentration of OH(aq) is strongly dependent onpH but is only weakly dependent on the sticking coefficient, the droplet radius, or the liquid water content of the cloud. Formic acid is rapidly produced by the aqueous‐phase reaction H2C(OH)2+ OH, but HCOO−is in turn rapidly oxidized by OH(aq). The HCOOH concentration in cloud is shown to be strongly dependent on cloud waterpH; clouds withpH greater than 5 are not efficient HCOOH sources. A novel mechanism is proposed for the oxidation of S(IV) by OH(aq). The main product is predicted to be HSO5−(peroxymonosulfate). Peroxymonosulfate appears to be stable in remote clouds and could contribute a large fraction of

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09807

年代:1986

数据来源: WILEY

摘要:

Mixing ratios of tropospheric CO as measured by an aircraft‐mounted radiometer over Saudi Arabia, the Arabian Sea, and northern India during May and June 1979 are reported. During early May, exceptionally high CO levels were detected over Saudi Arabia, and strong horizontal gradients in CO mixing ratios were seen to develop over a period of several days. Over the Arabian Sea, mixing ratios of the order of 150 parts per billion by volume were observed before the monsoon onset, and a pronounced decrease in CO was detected toward the equator. Subsequent measurements after the monsoon had become established revealed a consistent decrease in CO mixing ratio across this region. Analysis of aircraft dropsonde data and constant pressure daily streamline charts lend strong support to the hypothesis that this reduction is associated with the influx of CO‐poor southern hemisphere air in the monsoon southwesterl

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09827

年代:1986

数据来源: WILEY

摘要:

The instrumental and data reduction techniques used in obtaining remote measurements of carbon monoxide during the 1979 Summer Monsoon Experiment are described. The form of the signal function (the variation of signal with altitude) and the impact of variations in the vertical distribution of carbon monoxide are discussed. Estimates of the experimental accuracy are made both by assessment of error sources through the use of numerical simulations and by comparison with concurrent measurements made by means of gas chromatography. It is found that the radiometric measurements tend to be about 9% lower than the direct measurements and to have a precision of about 8%.

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09841

年代:1986

数据来源: WILEY

摘要:

Measurements of the chemical composition (Cl−, NO3−, SO42−, and H+) of ice core samples from Dye 3, Greenland, show recent increases in the concentration of nitrate and sulfate which can be attributed to anthropogenic sources. These anthropogenic sources have changed not only the magnitude of impurity levels in Greenland snow but also the seasonal pattern of impurity concentration. The observed change in seasonal deposition patterns between preindustrial and industrial times is used to analyze the sources of both natural and anthropogenic impurities in Gree

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09849

年代:1986

数据来源: WILEY

摘要:

Mutually consistent line‐by‐line, narrow‐band and broad‐band infrared radiation models are presented for methane, a potentially important anthropogenic trace gas within the atmosphere. Comparisons of the modeled band absorptances with existing laboratory data produce the best agreement when, within the band models, spurious band intensities are used which are consistent with the respective laboratory data sets, but which are not consistent with current knowledge concerning the intensity of the infrared fundamental band of methane. This emphasizes the need for improved laboratory band absorptance measurements. Since, when applied to atmospheric radiation calculations, the line‐by‐line model does not require the use of scaling approximations, the mutual consistency of the band models provides a means of appraising the accuracy of scaling procedures. It is shown that Curtis‐Godson narrow‐band and Chan‐Tien broad‐band scaling provide accurate means of accounting for atmospheric temperature and

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09857

年代:1986

数据来源: WILEY

摘要:

Laboratory kinetic studies suggest that an appreciable fraction of the ozone produced by recombination of atomic oxygen is vibrationally excited in the ν3mode. Further, laboratory data are available for the physical quenching of ν3, its radiative relaxation, and its radiative excitation by resonant absorption. It is shown that these chemical and physical processes are likely to result in substantial departures from local thermodynamic equilibrium for the ν3mode of ozone in the mesosphere and therefore have important effects on infrared mesospheric ozone measurements by emission in the 9.6‐μm band. Implications of these effects upon the Limb Infrared Monitor of the Stratosphere data, particularly their night/day ratio, are disc

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09865

年代:1986

数据来源: WILEY

摘要:

With the aid of new calculations on the transition moments between the six lowest states of O2, absorption cross sections have been calculated for several oxygen continua, including theA2Σu+←X3Σg−andA′3Δu←a1Δgsystems. Reasonable agreement is achieved with recent experimental results, the comparison indicating an overestimation of the theoretical transition moment for the A‐X system of 20–25%. With this adjustment, the calculated radiative lifetime for theO2(A) state is 150 ms, in close agreement with the currently used value. TheA′ ←aandA←Xcontinua cross sections are of similar magnitude, indicating that absorption by O2(a) cannot be a significan

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09877

年代:1986

数据来源: WILEY

摘要:

Observations by balloon‐borne instrumentation in the stratosphere (30–35 km) near Sondre Stromfjord, Greenland, have revealed disturbed vertical electric fields of the order of volts per meter of both polarities above an arctic storm system which moved onto the continent from the Davis Strait on August 11, 1982. This disturbance persisted at the balloon position for more than 10 hours, exhibiting order of magnitude variations with time scales ranging from minutes to hours. Simultaneous measurements of the stratospheric electrical conductivity did not show significant storm‐related variations. No lightning signals were detected, either at the balloon or at meteorological stations in the Davis Strait area. The disturbed field was predominantly downward (normal fair‐weather direction), and estimates of the total current indicate that at any instant a current of the order of 0.5 A was communicated to the storm system via the overlying stratosphere. The responsible storm system has been uniquely identified by NOAA 7 satellite IR (10.5–11.5 μm) imagery, and the infrared measurement of cloud‐top temperatures has revealed zones of enhanced convection lying in the storm's interior. Meteorological measurements taken at the surface and from balloon radiosondes by stations in the path of the storm also suggest that the storm possessed convective instabilities of the type likely to produce cloud electrification. In tropospheric features this type of storm occurs rather frequently on the western Greenland coast; therefore electrical charging of the storm cloud systems may not be as rare as indicated in the low probabilities observed for thunder a

ISSN:0148-0227    

DOI:10.1029/JD091iD09p09881

年代:1986

数据来源: WILEY