Assessing the relationships between elevation and extreme precipitation with various durations in southern Taiwan using spatial regression models

A spatially autocorrelated effect exists in precipitation of a mountainous basin. This study examines the relationship between maximum annual rainfall and elevation in the Kaoping River Basin of southern Taiwan using spatial regression models (i.e. geographically weighted regression (GWR), simultaneous autoregression (SAR), and conditional autoregression (CAR)). Results show that the GWR, SAR, and CAR models can improve spatial data fitting and provide an enhanced estimation for the rainfall–elevation relationship than the ordinary least squares approach. In particular, GWR achieves the most accurate estimation, and SAR and CAR achieve similar performance in terms of the Akaike information criterion. The relationship between extreme rainfall and elevation for longer duration is more concise than that for short durations. Results show that the spatial distribution of precipitation depends on elevation and that rainfall patterns in study area are heterogeneous between the southwestern plain and the eastern mountain area. Copyright © 2011 John Wiley & Sons, Ltd.     

Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver

Five vertical profiles of silver (Ag) in the subarctic northeast Pacific are presented. Dissolved (< 0.2 μm) Ag concentrations within the surface mixed layer range from 6–25 pM, with the highest observed values at the most coastal site. Elevated Ag concentrations at this station are most likely attributable to the estuarine circulation in the Juan de Fuca Strait. One open-ocean station (P20) exhibited a strong surface Ag maximum. The station was located at the edge of a Haida eddy which raises the possibility that such eddies transport Ag seaward from the coastal zone. Ag concentrations in the deep waters ranged from 60–80 pM. These measurements are consistent with other recent Ag data collected in the Pacific. Ag profiles throughout the Pacific Ocean yield a strong positive correlation between Ag concentration and dissolved silicic acid concentration. However, Ag is depleted relative to silicic acid at intermediate depths where dissolved O₂ concentrations are low, implying a possible removal of Ag from oxygen-depleted waters by scavenging and/or precipitation.     

Downstream effects of water withdrawal in a small,high-gradient basin: Erosion and deposition on the Skokomish River delta

This paper analyzes downstream effects of freshwater flow diversion from a small, active-continental-margin river basin. The Skokomish River delta, a tributary estuary to Hood Canal in Washington state, receives drainage from the southeastern side of the Olympic Mountains. Its drainage basin is steep, and rainfall is high. Since completion of two dams in 1930, approximately 40% of the annual average runoff of the entire system has been diverted from the North Fork Skokomish River for power production; this water does not pass through the lower river or over the delta. Extensive logging has occurred in the remainder of the basin. Comparison of prediversion (1885) and postdiversion (1941 and 1972) bathymetric surveys suggest that deposition (about 0.013 m yr^?1 to 0.022 m yr^?1) has occurred on most of the inner delta and erosion (up to 0.011 m yr^?1 to 0.033 m yr^?1) on much of the outer delta. More rapid postconstruction deposition occurred within the river mouth itself, where the 1926 to 1941 deposition rate was 0.04–0.11 m yr^?1. Nine of 12 historical bathymetric change cross-sections show steepening of the delta surface, two are neutral, and one shows aggradation. This steepening has apparently been caused by a loss of sediment transport capacity in the lower river and estuary combined with steady or increased (due to logging) sediment supply. Although the total area of unvegetated tidal flats has decreased by only about 2%, there has been a 15–19% loss of highly productive low intertidal surface area and an estimated 17% loss of eelgrass (Zostera marina) habitat. A reduction in the size of mesohaline mixing zone has also occurred. These habitat losses are similar to those observed elsewhere in the world in larger river basins that have suffered water withdrawals of the same magnitude, but their impacts either cannot be evaluated or understood casually through consideration of simple measures like changes in total estuarine deltaic area. Evaluation of estuarine effects of anthropogenic modification must, therefore, include consideration of both changes in habitat function and in the physical processes. These must be evaluated within the totality of the river basin-estuary system that cause these changes. In this case, sediment transport constitutes the critical link between fluvial alterations and the remote downstream, estuarine consequences thereof.     

A Method for the Exploratory Analysis of Airline Networks

The airline industry in the United States has experienced significant changes in the spatial configuration of networks since the Airline Deregulation Act of 1978. Attempts have been made to study the structure of the hub-and-spoke network in the airline industry, but no efficient methodology has been available. This paper describes an exploratory approach to analyzing the spatial configuration of airline networks. Flight frequencies and numbers of passengers from published schedules of six U.S. domestic airlines (American, Continental, Delta, Northwest, United, and USAir) are used in this study. The analytic components in the exploratory system include the examination of network connectivity and network autocorrelation in a dynamic mapping environment. The results of the analyses show both the overall spatial patterns of airline networks and the hierarchical hubbing structures.     

Low pressure radon diffusion: a laboratory study and its implications for lunar venting

Results of a study of radon migration through columns of fine particulate materials, at total pressures of 2–20 × 10^?2 torr, are reported. Materials studied were: NBS Glass Spheres (SRM 1003), Emerson & Cuming Eccospheres (IG-101), activated coconut charcoal, Lipari obsidian, and W-1 Standard Diabase. Rates of diffusion were used to derive heats of adsorption for radon on the materials tested. The most reliable values found clustered around 8–9 kcal/mole.These high heats of adsorption, if typical for most materials, combined with low percentages of radon emanation by lunar soils found by other researchers, imply that random walk diffusion will not be an important mechanism for redistributing the radon and the radon daughters produced in the lunar regolith. In particular, since random walk migration is not a sufficient mechanism to account for localized high concentrations of radon-222 and its daughter polonium-210 observed by the Apollo 15 and 16 command modules, an alternative mechanism is proposed, in which radon would be swept to the surface by other gases during intermittent venting events.     

Elastic properties from acoustic and volume compression experiments

Hydrostatic compression data for a number of high-pressure phases of oxides and silicates, which have been studied independently by acoustic techniques, have been analyzed by least-squares fitting of the Birch-Murnaghan equation of state to determine the zero-pressure bulk modulus K₀ and its pressure derivative K′₀ for each material. The standard deviations of K₀ and K′₀ so determined are generally underestimated unless the experimental errors in the measurements of volume and pressure are explicitly included. When the values of K₀ determined from the acoustic and compression techniques are consistent, test results for quartz and rutile demonstrate that constraining K₀ to be equal to the acoustic value significantly improves both the accuracy and the precision of K′₀ obtained from the compression data. Similar analyses for high-pressure phases (e.g., pyrope garnet and silicate spinels) indicate that by combining the acoustic and P-V data, the standard deviation of K′₀ is typically reduced by a factor of three. Thus, we conclude that this approach does allow precise determinations of K′₀ even when neither technique alone is able to resolve this parameter. For some materials, however, the P-V and acoustic experiments do not define mutually consistent values of K₀, invalidating any combination of these data. The compression data for stishovite clearly exhibit run to run effects, and we infer that systematic errors are present in some of the P-V data which are responsible for many of the interlaboratory inconsistencies. Such systematic biases in the P-V data can at least be partially compensated for by performing several duplicate experimental runs.     

Shear stress on the base of a lithospheric plate

This paper is a review of the theoretical and observational evidence bearing on the magnitude of the shear stress which acts on the base of a lithospheric plate. Estimates based on the viscosity of the upper mantle do not yield useful limits. Arguments based on the thermal stability of the upper mantle indicate that the basal shear stress is no larger than a few bars. An indirect measurement of the rheology and shear stress can be made by studying the diffusion of stress and displacement following a large decoupling earthquake. When applied to the 1965 Rat Island Earthquake, this method yields a basal shear stress of about 2 bars. These results indicate that for small plates the forces produced by basal shear stress are probably small in comparison with forces acting on plate boundaries. To a first approximation, the smaller plates act as if they were decoupled from the mantle below. These stress estimates lead to a model in which the motion of the smaller lithospheric plates is governed almost entirely by the forces acting on their edges. Forces due to basal shear stress may be comparable to forces acting on the edges of large lithospheric plates. Thus, complete decoupling may not be a good approximation for such plates.