The global joule heat production rate and the AE index

The accuracy of the AE index as a measure of the joule heat production rate is examined for a typical substorm event on 18 March 1978 by estimating the global joule heat production rate, as a function of time, using data obtained from the IMS six meridian chains. In spite of the fact that the AE index had had an initial slow growth which was followed by a rapid growth, the joule heat production rate attained a high level during the slow growth and thus their variations were considerably different from those of the AE index. Therefore, although the AE index is statistically linearly related to the global joule heat production rate, one should be cautious in assuming that details of time variations of the AE index during individual events represent those of the joule heat production rate.     

A comparison of several wave spectra for the random wave diffraction by a semi-infinite breakwater

A comparison of the diffraction of multidirectional random waves using several selected wave spectrum models is presented in this paper. Six wave spectrum models, Bretschneider, Pierson–Moskowitz, ISSC, ITTC, Mitsuyasu, and JONSWAP spectrum, are considered. A discrete form for each of the given spectrum models is used to specify the incident wave conditions. Analytical solutions based on both the Fresnel integrals and polynomial approximations of the Fresnel integrals and numerical solutions of a boundary integral approach have been used to obtain the two-dimensional wave diffraction by a semi-infinite breakwater at uniform water depth. The diffraction of random waves is based on the cumulative superposition of linear diffraction solution. The results of predicted random wave diffraction for each of the given spectrum models are compared with those of the published physical model presented by Briggs et al. [1995. Wave diffraction around breakwater. Journal of Waterway, Port, Coastal and Ocean Engineering—ASCE 121(1), 23–35]. Reasonable agreement is obtained in all cases. The effect of the directional spreading function is also examined from the results of the random wave diffraction. Based on these comparisons, the present model for the analysis of various wave spectra is found to be an accurate and efficient tool for predicting the random wave field around a semi-infinite breakwater or inside a harbor of arbitrary geometry in practical applications.     

Hydrologic modelling of the effect of snowmelt and temperature on a mountainous watershed

Snowmelt-runoff modelling in a mountainous basin is perceived as difficult due to the complexity of simulation. Theoretically, the snowmelt process should be influenced by temperature changes. It is still controversial as how to incorporate the temperature changes into the snowmelt-runoff model in a mountainous basin. This paper presents the results of a study in the North Fork American River basin where the snowmelt-runoff mechanism is modelled by relating the temperature changes to the elevation band in the basin. In this study, a distributed hydrologic model is used to explore the orographic effects on the snowmelt-runoff using the snowfall-snowmelt routine in Soil and Water Assessment Tool (SWAT). Three parameters, namely maximum snowmelt factor, minimum snowmelt factor, and snowpack temperature lag were analysed during the simulation. The model was validated using streamflow data from October 1, 1991 to September 30, 1994 with and without considering the elevation band. The result of this study suggests that the snowmelt-runoff model associated with the elevation band better represents the snowmelt-runoff mechanism in terms of Nash–Sutcliffe coefficient (E _NS ), R ², and Root Mean Square Error (RMSE).     

Nature of polymerization and properties of silicate melts and glasses at high pressure

The structures of sodium silicate and aluminosilicate glasses quenched from melts at high pressure (6-10 GPa) with varying degrees of polymerization (fractions of nonbridging oxygen) were explored using solid-state NMR [¹⁷O and ²⁷Al triple-quantum magic-angle spinning (3QMAS) NMR]. The bond connectivity in melts among four and highly coordinated network polyhedra, such as ^[4]Al, ^[5,6]Al, ^[4]Si, and ^[5,6]Si, at high pressure is shown to be significantly different from that at ambient pressure. In particular, in the silicate and aluminosilicate melts, the proportion of nonbridging oxygen (NBO) generally decreases with increasing pressure, leading to the formation of new oxygen clusters that include 5- and 6-coordinated Si and Al in addition to 4-coordinated Al and Si, such as ^[4]Si-O-^[5,6]Si, ^[4]Si-O-^[5,6]Al and Na-O-^[5,6]Si. While the fractions of ^[5,6]Al increase with pressure, the magnitude of this increase diminishes with increasing degrees of ambient-pressure polymerization under isobaric conditions. Incorporating the above structural information into models of melt properties reproduces the anomalous pressure-dependence of O²⁻ diffusivity and viscosity often observed in silicate melts.     

Changes of precipitation extremes over South Korea projected by the 5 RCMs under RCP scenarios

The change of extreme precipitation is assessed with the HadGEM2-AO - 5 Regional Climate Models (RCMs) chain, which is a national downscaling project undertaken cooperatively by several South Korean institutes aimed at producing regional climate change projection with fine resolution (12.5 km) around the Korean Peninsula. The downscaling domain, resolution and lateral boundary conditions are held the same among the 5 RCMs to minimize the uncertainties from model configuration. Climatological changes reveal a statistically significant increase in the mid-21st century (2046- 2070; Fut1) and the late-21st century (2076-2100; Fut2) precipitation properties related to extreme precipitation, such as precipitation intensity and average of upper 5 percentile daily precipitation, with respect to the reference period (1981-2005). Changes depending on the intensity categories also present a clear trend of decreasing light rain and increasing heavy rain. In accordance with these results, the change of 1-in-50 year maximum precipitation intensity over South Korea is estimated by the GEV method. The result suggests that the 50-year return value (RV50) will change from -32.69% to 72.7% and from -31.6% to 96.32% in Fut1 and from -31.97% to 86.25% and from -19.45% to 134.88% in Fut2 under representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively, at the 90% confidence level. This study suggests that multi-RCMs can be used to reduce uncertainties and assess the future change of extreme precipitation more reliably. Moreover, future projection of the regional climate change contains uncertainties evoked from not only driving GCM but also RCM. Therefore, multi-GCM and multi-RCM studies are expected to provide more robust projection.     

Analytical exploration of γ-function explicit method for pseudodynamic testing of nonlinear systems

It has been well studied that the γ-function explicit method can be effective in providing favorable numerical dissipation for linear elastic systems. However, its performance for nonlinear systems is unclear due to a lack of analytical evaluation techniques. Thus, a novel technique is proposed herein to evaluate its efficiency for application to nonlinear systems by introducing two parameters to describe the stiffness change. As a result, the numerical properties and error propagation characteristics of the γ-function explicit method for the pseudodynamic testing of a nonlinear system are analytically assessed. It is found that the upper stability limit decreases as the step degree of nonlinearity increases; and it increases as the current degree of nonlinearity increases. It is also shown that this integration method provides favorable numerical dissipation not only for linear elastic systems but also for nonlinear systems. Furthermore, error propagation analysis reveals that the numerical dissipation can effectively suppress the severe error propagation of high frequency modes while the low frequency responses are almost unaffected for both linear elastic and nonlinear systems.     

Derivative‐Assisted Classification of Fractured Zones Crossing a Deep Borehole

In this study, the derivative analysis using the derivative of drawdown with respect to log‐time was utilized to determine candidates for hydraulic conductor domains (HCDs). At a 500‐m deep borehole in the study site, the fractured rocks crossing the borehole were first classified in fractured and nonfractured zones by core logging and geophysical loggings, such as acoustic televiewing, density, and flow loggings. After conducting the hydraulic tests such as constant head withdrawal and recovery tests at the fractured zones and the nonfractured zones, the derivative analyses were carried out, of which the results were evaluated to determine the candidates for HCDs. For the nonfractured zones, the diagnostic plot has only a big hump indicating poor connection of the background fractures to the permeable geologic media, while those of the candidates for HCDs show various flow regimes. On the basis of these results, the candidates for HCDs among the fractured zones were determined. From discussion on the results, the combination of the spacing analysis and derivative analysis following a hydraulic test is recommended for determining the candidates for HCDs rather than other geophysical loggings.     

东亚夏季风降水和环流数值模拟对不同对流参数化方案的敏感性

A 5-level spectral AGCM (ImPKU-5LAGCM) is used to examine the sensitivity of the simulated results of the summer monsoon rainfall and circulation in East Asia to different cumulus parameterization schemes in the climatological-mean case and in the cases of weak and strong Asian summer monsoons,respectively. The results simulated with the Arakawa-Schubert＇s(hereafter A-S＇s), Kuo＇s and Manabe＇s cumulus parameterization schemes show that these simulated distributions of the summer monsoon rainfall and circulation in East Asia depend strongly on the cumulus parameterization schemes either in the climatological-mean case or in the cases of weak and strong Asian summer monsoons. From the simulated results, it might be shown that the Kuo scheme appears to be more suitable for the simulation of the summer monsoon rainfall and circulation in East Asia than the A-S scheme or the Manabe scheme, although the A-S scheme is somewhat better in the simulations of the tropical rainfall. This might be due to that the Kuo＇s cumulus parameterization scheme is able to reflect well the characteristics of rainfall cloud system in the East Asian summer monsoon region, where the rainfall system used to be a mixing of cumulus and stratus.     

Analysis of resistivity data obtained from cone penetrometer in contaminated soil layers

In horizontally layered soils of different electrical properties, electrical potential distribution becomes complex and the obtained resistivity data may be limited in reflecting the actual soil profile. Thus the objective of this study was to identify the factors that affect resistivity measurement on the cone penetrometer and further investigate the sensitivity of measured resistivity to different types and concentrations of contaminants at the subsurface level. First, a theoretical resistivity equation was derived to provide a means of computing the geometric factor. The effective volume of measurement on the cone penetrometer was investigated and laboratory soil box tests verified the dominance of partially high resistivity regions within the effective volume of measurement over the apparent resistivity. Such effect was found to lead to possible discrepancies between the recorded resistivity data and the actual depth of measurement. Measurements on contaminated soil layers indicated that resistivity cones are efffective in delineating inorganic contaminants in soils of high water contents, and detecting NAPLs floating above the groundwater table provided that soils adjacent to the plume are not dry of water. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.