摘要:

Hundreds of chemical compounds have been identified as constituents of atmospheric aerosols and raindrops, and there is substantial evidence for chemical transformations occurring among them. Since tropospheric aerosols have a water content of 30–50 wt % at typical relative humidities, aerosols and raindrops may be regarded (at least to a first approximation) as aqueous solutions. In this review, atmospheric measurements and solution chemistry data are combined to examine reactions and physical parameters of potential importance in aerosol and raindrop systems; much of the information is potentially applicable as well to lake and ocean surface waters. Among the conclusions are the following: (1) Solar radiation penetrates aqueous aerosols and raindrops, photodissociating several molecules and ions. H2O2, formed in the gas phase and dissolved in the aerosol, photodissociates to produce OH ·, which is thus a common constituent of aqueous atmospheric systems and appears to play a role in many chemical processes. (2) The decomposition of atmospheric ozone dissolved in aqueous aerosols or raindrops is a second prolific source of HOx· radicals. (3) An analysis of the transition metal chemistry appropriate to these systems indicates that copper, manganese, and vanadium are potentially the most important homogeneous catalysts and that the concentrations of transition metals in aerosols are significant. (4) The oxidations of alkanes to alcohols, of alcohols to aldehydes, and of aldehydes to carboxylic acids result from chemical chains initiated by hydroxyl radicals or perhaps by organic photochemistry. (5) Rate parameters are available for many of the reactions of interest, particularly for the inorganic processes. Tabulations of relevant rate parameters, absorption coefficients, equilibrium constants, and aqueous solubilities are presented. (6) The tropospheric aerosol can be viewed schematically as an aqueous solution surrounding an insoluble core and covered by an organic surface film of varying integrity, thickness, and composit

ISSN:8755-1209    

DOI:10.1029/RG019i004p00505

年代:1981

数据来源: WILEY

摘要:

The difficult problem of parameterizing tropical convection in large‐scale models of the atmosphere led to the Global Atmospheric Research Program’s Atlantic Tropical Experiment (GATE), whose goal was to improve basic understanding of tropical convection and its role in the global atmospheric circulation. A dense network of instrumented ships equipped with upper air sounding equipment and quantitative weather radars were located over the Atlantic Ocean, in the intertropical convergence zone (ITCZ), just west of equatorial Africa. The ship network was supplemented by a fleet of research aircraft and a geosynchronous meteorological satellite. The data obtained show that the deep convection in the ITCZ was concentrated in two types of ‘cloud clusters,’ rapidly moving squall clusters, and slowly moving nonsquall clusters. The clusters were characterized by large mid‐to‐upper level cloud shields, or ‘anvil clouds,’ that emanated from penetrative cumulonimbus convection. Accompanying the deep cumulonimbus in each cluster was a log normal spectrum of smaller convective features ranging from moderate cumulonimbus down to tiny nonprecipitating cumulus. The large cumulonimbus were typically grouped within a cluster into one or more mesoscale precipitation features (or MPF’s), which were apparently triggered in mesoscale regions of intensified low‐level convergence. As an MPF matured it developed a region of stratiform precipitation adjacent to its active deep convective cells. The stratiform precipitation fell from the anvil cloud. Associated with the stratiform precipitation were a mesoscale downdraft below the anvil cloud and an apparent mesoscale updraft within the anvil cloud itself, above the mesoscale downdraft. These mesoscale drafts were distinct from the convective‐scale updrafts and downdrafts of the cumulus and cumulonimbus cells of the cluster. Downdrafts, both convective scale and mesoscale, filled the planetary boundary layer in the vicinity of cumulonimbus with stable air of low moist static energy. These wakes of downdraft air exerted a strong control on where future convection broke out. The results of GATE show that to simulate the effects of tropical convection in large‐scale numerical models of the atmosphere a variety of phenomena must be accounted for, including not only convective‐scale updrafts and downdrafts but anvil clouds with mesoscale updrafts and downdrafts, downdraft‐induced boundary layer transformations, and mesoscale convergence patterns. Experimentation with ways of including some of these features of tropical convection in large‐scale diagnostic and prognostic studies is under way, but

ISSN:8755-1209    

DOI:10.1029/RG019i004p00541

年代:1981

数据来源: WILEY

摘要:

The buildup of static charge on satellite surfaces is an important issue in the utilization of satellite systems. The analysis of this phenomenon has required important advances in basic charging theory and the development of complex codes to evaluate the plasma sheaths that surround satellites. The results of these theories and calculations have wide application in space physics in the design of systems and in the interpretation of low‐energy plasma measurements. In this review, those aspects of charge buildup on satellite surfaces relevant to the space physics community are summarized. The types of charging processes, models of charge buildup, satellite sheath theories, and charging observations are described with emphasis on basic concept

ISSN:8755-1209    

DOI:10.1029/RG019i004p00577

年代:1981

数据来源: WILEY

摘要:

The duality between electric current and magnetic flux tubes is outlined for the magnetosphere. Magnetic flux tubes are regarded as fluid elements subject to various stresses. Current closure then becomes the dual of stress balance, and Poynting vector energy flow a dual ofJ · Edissipation. The stresses acting on a flux tube are magnetic stresses, which correspond to currents at a distance, and plasma stresses, which correspond to local currents. The duality between current and stress is traced for ionospheric ion drag forces, solar wind stresses at the magnetopause, inertial effects, and the effects of energetic plasma on flux tubes. The stress balance and dual current systems are outlined for idealized magnetospheres of increasing complexity. For a simple magnetosphere with no convective flow, the balanced stresses are solar wind pressure and neutral sheet plasma pressure. The corresponding current systems are the Chapman‐Ferraro magnetopause currents and the magnetotail current system. The introduction of convective flow introduces further stresses: ionospheric ion drag, Alfvén layer shielding, and an imbalance in day‐night magnetic stresses due to transport of flux tubes to the nightside by the solar wind. These stresses balance, and hence the corresponding additional currents (the ionospheric Pedersen current and the electrojets, the partial ring current, and two other current systems from the magnetopause and tail) must form a closed current system and do so by the region I and II field‐aligned currents of Iijima and Potemra. The energy flow in the above models is described in terms of both Poynting vectors and the above current systems. Temporal variations examined are (1) an increase in dayside merging and/or nightside reconnection, (2) an increase in the energy density of plasma in the plasma sheet, (3) an increase in ionospheric conductivity, and (4) an increase in solar wind pressure. Each of the first three requires an increase in all the currents and stresses associated with convective flow. The symptoms of variation 3 are very similar to many of those observed during magnetospheric substorms, and it is concluded that ionospheric conductivity enhancement is important in substorms, since it represents a major change in the forces affecting the flow and, in the dual picture, of the currents associated with the flow. Finally, the effect of aurora‐associated magnetic‐field‐aligned electric fields are considered, and the variation in the flows when the east‐west component of electric field parallel to the arc is included. Quite different plasma transport may result even though the north‐south meridian cross sect

ISSN:8755-1209    

DOI:10.1029/RG019i004p00617

年代:1981

数据来源: WILEY

摘要:

A number of theories have been proposed in recent years to explain auroral kilometric radiation. These include an anisotropic velocity distribution instability, mode conversion of electron cyclotron waves to ordinary mode radiation, soliton radiation, beam‐driven instability of electromagnetic waves via low‐frequency turbulence, a loss cone instability, beating of coherent electrostatic waves, and beam amplification of electromagnetic waves via coherent density fluctuations. These will all be reviewed, and comparisons of prediction made with observations. Emphasis will be placed on the three recent propos

ISSN:8755-1209    

DOI:10.1029/RG019i004p00627

年代:1981

数据来源: WILEY

摘要:

Sediments in the Great Lakes are subject to four general categories of processes: input, transport, deposition, and postdepositional alteration. Sedimentary input is from coastal erosion (64%), riverine input (26%), atmospheric transport (3%), and several lesser sources (7%). Once in the lake, sediments are transported to their place of deposition along the bottom and/or in suspension depending upon grain size and density. The rate of deposition in the Great Lakes is variable and ranges from zero in some areas to over 6000 g m−2yr−1in the eastern basin of Lake Erie. After deposition, sediments undergo bioturbation, dissolution of carbonate and opal, remobilization of many metals followed by reprecipitation within the surficial oxidized layer, and degradation of organic compou

ISSN:8755-1209    

DOI:10.1029/RG019i004p00635

年代:1981

数据来源: WILEY

摘要:

Various magnitude scales commonly used and the interrelationships among them are reviewed. It is shown that problems exist with all of the magnitude scales being used in the United States. When using regional catalogs, for example, it is often necessary to determine how the reported magnitudes were determined. Often such information is not available, although the potential errors are quite large. Both theMSand thembscales were designed to be universal scales. However, bothMSandmbmagnitudes are often determined beyond the applicable range of the equations used to define the two scales. Furthermore, theMSmagnitudes are not generally available for moderate to small earthquakes in most earthquake catalogs. Thembmagnitudes are more generally available thanMSvalues; however, there is also much greater variation in the waymbis determined. In particular, a significant change in thembscale occurred in the early 1960’s when the World‐Wide Standard Seismograph Network (WWSSN) was established. This change in instrumentation used to determinembvalues had a significant effect on estimated magnitudes (post‐1960 values are lower) and the saturation level of thembscale. The older, longer‐period instruments recorded largermbmagnitudes than can be recorded with the WWSSN instruments. In addition, great care must be taken when selecting thembmagnitudes of western U.S. earthquakes, because the values are often in considerable error owing to the fact that they were determined at distances less than 25° and were not properly corrected for attenuation in the upper mantle, or asthenosphere. The seismic body wave magnitudembof an earthquake is strongly affected by regional variations in theQstructure, composition, and physical state within the earth. Therefore because of differences in attenuation ofPwaves between the western and eastern United States, a problem arises when comparingmbvalues for the two regions. A regionalmbmagnitude bias exists which, depending on where the earthquake occurs and where thePwaves are recorded, can lead to magnitude errors as large as ⅓ unit. There is also a significant difference betweenmbandMLvalues for earthquakes in the western United States. An empirical link between thembof an eastern U.S. earthquake and theMLof an equivalent western earthquake is given byML= 0.57 + 0.92(mb)east. This result is important when comparing ground motion between the two regions and for choosing a set of real western U.S. earthquake records to represent eastern e

ISSN:8755-1209    

DOI:10.1029/RG019i004p00649

年代:1981

数据来源: WILEY

摘要:

Theoretical considerations, laboratory experiments, and limited field data support a value of 3 for the exponentnin the commonly used empirical flow law ϵ = (τ/B)nrelating stress and strain rate in polycrystalline ice. If this value is accepted, the viscosity parameterBcan be determined for a wide variety of experiments. In a plot of logBagainst reciprocal temperature, points scatter about a line defined by an empirical equation of the formB=B0exp {(T0/T) ‐ [C/(Tr‐T)k]}, whereTis the temperature in kelvins andB0,C,T0,Tr, andkare empirically determined constants. For laboratory data the scatter is equivalent to approximately a factor of 5 variation in strain rate for a given stress and temperature. The cause of this variation is unclear, but because results from any single laboratory are generally internally consistent, sample preparation procedures should be studied. Field experiments yield values ofBthat are systematically higher than laboratory results. Thus natural ice appears stronger than laboratory ice, despite the coarser texture and the presence of anisotropic fabrics in the natural ice, both of which should tend to soften it. In addition, natural ice in glaciers appears stronger than natural ice deformed in the laboratory. These observations suggest either that the stress is systematically overestimated in field studies or that a flow law based on the von Mises yield criterion (or the second invariant of the stress deviator tensor) does not provide an adequate description of the deformation of ice in multiaxial stress f

ISSN:8755-1209    

DOI:10.1029/RG019i004p00664

年代:1981

数据来源: WILEY

摘要:

In the last 20 years statistical methods have been applied in geodesy with considerable success, both in physical geodesy (least squares collocation, variance‐covariance propagation) and in geodetic measuring technique (error propagation and interpolation, inertial navigation, adjustment, diagnosis, and design of networks). The geodetic stochastic process is introduced per definition as the representation of a geophysical random field afflicted with observational errors, including the special cases of the (almost) error‐free field (physical‐geodetic process) and the pure error field (operational‐geodetic process). Geodesy is an approximation science, planar approximation being of great practical importance. It can be realized by projection onto a tangential plane to the earth’s surface and/or other planes of measurement and computation. The review treats the covariance functions of planar processes for different geodetic problems in the light of literature on the subject and under systematizing aspects—inter alia, gravity field, field of atmospheric refraction, error field; covariance estimation and propagation; ideal statistical structures as homogeneity, isotropy, axisymmetry, but also the physical, statistical, and geophysical significance of the prerequisites and solutions as well as problems that are sti

ISSN:8755-1209    

DOI:10.1029/RG019i004p00673

年代:1981

数据来源: WILEY

ISSN:8755-1209    

DOI:10.1029/RG019i004p00687

年代:1981

数据来源: WILEY