摘要:

Until recently, very little progress had been made in understanding the relationship between small‐scale variability of topography, soil, and rainfalls and the storm response seen at the catchment scale. The work reviewed here represents the first attempt at a systematic theoretical framework for such understanding in the context of surface runoff generation by different processes. The parameterization of hydrological processes over a range of scales is examined, and the concept of the “representative elementary area” (REA) is introduced. The REA is a fundamental scale for catchment modeling at which continuum assumptions can be applied for the spatially variable controls and parameters, and spatial patterns no longer have to be considered explicitly. The investigation of scale leads into the concept of hydrologic similarity in which the effects of the environmental controls on runoff generation and flood frequency response be investigated independently of catchment scale. The paper reviews the authors' initial results and hopefully will motivate others to also investigate the issues of hydrologic scale and simil

ISSN:8755-1209    

DOI:10.1029/RG028i001p00001

年代:1990

数据来源: WILEY

摘要:

The lithosphere of the Earth can be viewed as a hierarchy of volumes, from tectonic plates to grains of rock. Their relative movement against the forces of friction and cohesion is realized to a large extent through earthquakes. The movement is controlled by a wide variety of independent processes, concentrated in the thin boundary zones between the volumes. A boundary zone has a similar hierarchical structure, consisting of volumes, separated by boundary zones, etc. Altogether, these processes transform the lithosphere into a large nonlinear system, featuring instability and deterministic chaos. From this background some integral grossly averaged empirical regularities emerge, indicating a wide range of similarity, collective behavior, and the possibility of intermediate‐term earthquake predictio

ISSN:8755-1209    

DOI:10.1029/RG028i001p00019

年代:1990

数据来源: WILEY

摘要:

This paper provides a general overview of the issues related to the modeling of surface processes in atmospheric models. The role of surface processes is first discussed as an essential coupling between the surface and the atmosphere. The issue of parameterization of small‐scale processes in large‐scale atmospheric models is addressed next, paying special attention to the cases of bare ground and vegetated surfaces. The paper focuses on the issues rather than the details of implementation, and extensive citations to the published literature are given for further investigati

ISSN:8755-1209    

DOI:10.1029/RG028i001p00035

年代:1990

数据来源: WILEY

摘要:

Chemical weathering processes, essentially caused by the interaction of water and the atmosphere with the Earth's crust, transform primary minerals into solutes and clays and, eventually, into sedimentary rocks; these processes participate in controlling the global hydrogeochemical cycles of many elements. Many mineral dissolution processes are controlled by a chemical mechanism at the solid‐water interface. The reaction‐controlling steps can be interpreted in terms of a surface coordination model. The tendency of a mineral to dissolve is influenced by the interaction of solutes—H+, OH−, ligands, and metal ions—with its surface. The surface reactivity is shown to depend on the surface species and their structural identity; specifically, the dependence of dissolution rates onpH and on dissolved ligand concentrations can be explained in terms of surface protonation (and deprotonation) and of ligand surface complexes. A general rate law for the dissolution of minerals is derived by considering, in addition to the surface coordination chemistry, established models of lattice statistics and activated compl

ISSN:8755-1209    

DOI:10.1029/RG028i001p00053

年代:1990

数据来源: WILEY

摘要:

We review indications of persistent deviations from the geocentric axial dipole model of the time‐averaged geomagnetic field and present a zonal harmonic model derived from 185 deep‐sea sediment piston cores taken from low to middle latitudes (to approximately ±45°). Analysis of the paleomagnetic inclination recorded in these cores for the Brunhes (normal polarity; 0–73 Ma) and Matuyama (reverse polarity; 0.73–2.47 Ma) chrons, after plate motion correction, gives well‐constrained estimates of the dominant long‐term nondipole contributions (the axial quadrupole and axial octupole) and shows no significant deviation from axial symmetry. The amplitude of the axial quadrupole is found to vary with polarity (2.6% of the geocentric axial dipole for normal; 4.6% for reverse), while the axial octupole does not show appreciable change (−2.9% for normal; −2.1% for reverse). These estimates of the quadrupole contribution agree well with prior determinations for the Plio‐Pleistocene (0–5 Ma); however, the octupole contribution we find is opposite in sign to previous estimates. We suggest that a negative octupole is representative of the actual time‐averaged paleomagnetic field, while prior positive octupole estimates probably reflect spurious inclination shallowing. The lack of polarity asymmetry in the octupole suggests that this nondipole component may be more closely linked to the main dipole field than is the quadrupole and so supports models of the geodynamo in which dipole and quadrupole f

ISSN:8755-1209    

DOI:10.1029/RG028i001p00071

年代:1990

数据来源: WILEY

摘要:

There is a growing anticipation among space scientists that a Pioneer or Voyager spacecraft will soon pass through one of the last major frontiers in the solar system—the heliospheric terminal shock. Some unknown, but perhaps small, distance beyond the terminal shock is the heliopause, marking the final boundary between solar wind and galactic plasmas and the final goal of these spacecraft. This occasion is drawing widespread attention because of the opportunity it offers to obtain a wealth of information on the properties of the galaxy, the interstellar medium, and the large‐scale interactions of that medium with stellar winds. The anticipation has been raised by several tentative remote detections of the shock placing it just beyond the present spacecraft locations. However, uncertainties in the physical processes and parameters that determine the location of the boundary lead to equal uncertainties in predicting which of the spacecraft will reach it first. This review is largely phenomenological with the intent of providing an overview of the topic and the dominant physical proces

ISSN:8755-1209    

DOI:10.1029/RG028i001p00097

年代:1990

数据来源: WILEY