A spatial analysis of hydro‐climatic and vegetation condition trends in the Yellow River basin

Stream‐gauge data indicate that the flow of the Yellow River has declined during the past several decades. Zero flow in sections of the river channel, i.e. the Yellow River drying‐up phenomenon, has occurred since the 1970s. In this paper we present an analysis of changes in the spatial patterns of climatic and vegetation condition data in the Yellow River basin based on data from meteorological stations and satellites. The climatic data are from 1960 to 2000 and the vegetation condition data are from 1982 to 2000. The angular‐distance‐weighted interpolation method is used to get climatic data coverage from station observations. The spatial distribution of tendency is detected with Student's t‐test. The spatial patterns of climatic and vegetation condition change was analysed together with the statistical data on human activities. The analysis indicates that the precipitation decreases and temperature increases in most parts of the Yellow River basin, the evaporative demand of the atmosphere decreases in the upper reaches and increases in the lower reaches, and human activities have improved the vegetation condition in the irrigation districts. The Loess Plateau, the Tibetan Plateau, and the irrigation districts are respectively suggested as precipitation, temperature, and human activity hot spots of the Yellow River drying‐up phenomenon. Copyright © 2007 John Wiley & Sons, Ltd.     

Field experiments on remediation of coastal sediments using granulated coal ash

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1–2.4 mg S L⁻¹ in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.     

On the relationship between the Bowen ratio and the near-surface air temperature

The sensitivity of land surface energy partitioning to near-surface air temperature (T _a) is a critical issue to understand the interaction between land surface and climatic system. Thus, studies with in situ observed data compiled from various climates and ecosystems are required. The relations derived from such empirical analyses are useful for developing accurate estimation methods of energy partitioning. In this study, the effect of T _a on land surface energy partitioning is evaluated by using flux measurement data compiled from a global network of eddy covariance tower sites (FLUXNET). According to the analysis of 25 FLUXNET sites (60 site-years) data, the Bowen ratio is found to have a linear relation with the bulk surface resistance normalized by aerodynamic and climatological resistance parameters in general, of which the slope and intercept are dependent on T _a. Energy partitioning in warmer atmosphere is less sensitive to changes in land surface conditions. In addition, a negative relation is found between Bowen ratio and T _a, and this relation is stronger above less vegetated surface and under low vapor pressure deficit and low received radiative energy condition. The empirical results obtained in this study are expected to be useful in gaining better understanding of alternating surface energy partitioning under increasing T _a.     

Developing an overall assessment map for flood hazard on large area watershed using multi-method approach: case study of Wadi Qena watershed,Egypt

Natural Hazards - Many parts of Upper Egypt as Sinai and Red Sea areas were hit by severe flash floods since 1976. Wadi Qena is considered one of the most watersheds that suffers from floods in Red...     

Water and heat fluxes above a lowland dipterocarp forest in Peninsular Malaysia

We measured the fluxes of sensible and latent heat between a low‐land dipterocarp forest in Peninsular Malaysia and the atmosphere. No clear seasonal or interannual changes in latent heat flux were found from 2003 to 2005, while sensible heat flux sometimes fluctuated depending on the fluctuation of incoming radiation between wet and dry seasons. The evapotranspiration rates averaged for the period between 2003 and 2005 were 2·77 and 3·61 mm day^?1 using eddy covariance data without and with an energy balance correction, respectively. Average precipitation was 4·74 mm day^?1. Midday surface conductance decreased with an increasing atmospheric water vapour pressure deficit and thus restricted the excess water loss on sunny days in the dry season. However, the relationship between the surface conductance and vapour pressure deficit did not significantly decline with an increase in volumetric soil water content even during a period of extremely low rainfall. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrogen isotopes in volcanic plumes: Tracers for remote temperature sensing of fumaroles

In high-temperature volcanic fumaroles (>400 °C), the isotopic composition of molecular hydrogen (H₂) reaches equilibrium with that of the fumarolic H₂O. In this study, we used this hydrogen isotope exchange equilibrium of fumarolic H₂ as a tracer for the remote temperature at volcanic fumaroles. In this remote sensing, we deduced the hydrogen isotopic composition (δD value) of fumarolic H₂ from those in the volcanic plume. To ascertain that we can estimate the δD value of fumarolic H₂ from those in a volcanic plume, we estimated the values in three fumaroles with outlet temperatures of 630 °C (Tarumae), 203 °C (Kuju), and 107 °C (E-san). For this we measured the concentration and δD value of H₂ in each volcanic plume, along with those determined directly at each fumarole. The average and maximum mixing ratios of fumarolic H₂ within a plume’s total H₂ were 97% and 99% (at Tarumae), 89% and 96% (at Kuju), and 97% and 99% (at E-san). We found a linear relationship between the depletion in the δD values of H₂, with the reciprocal of H₂ concentration. Furthermore, the estimated end-member δD value for each H₂-enriched component (−260 ± 30‰ vs. VSMOW in Tarumae, −509 ± 23‰ in Kuju, and −437 ± 14‰ in E-san) coincided well with those observed at each fumarole (−247.0 ± 0.6‰ in Tarumae, −527.7 ± 10.1‰ in Kuju, and −432.1 ± 2.5‰ in E-san). Moreover, the calculated isotopic temperatures at the fumaroles agreed to within 20 °C with the observed outlet temperature at Tarumae and Kuju. We deduced that the δD value of the fumarolic H₂ was quenched within the volcanic plume. This enabled us to remotely estimate these in the fumarole, and thus the outlet temperature of fumaroles, at least for those having the outlet temperatures more than 400 °C. By applying this methodology to the volcanic plume emitted from the Crater 1 of Mt. Naka-dake (the volcano Aso) where direct measurement on fumaroles was impractical, we estimated that the δD value of the fumarolic H₂ to be −172 ± 16‰ and the outlet temperature to be 868 ± 97 °C. The remote temperature sensing using hydrogen isotopes developed in this study is widely applicable to many volcanic systems.     

Progressive ordering of cristobalitic silica in the early stage of diagenesis

Examination of hydrothermally transformed silica from controlled experiments reveals that amorphous silica changes to quartz through an intermediate phase of opal-CT and that the d(101) spacing of cristobalite progressively decreases from 4.10 Å to 4.05 Å. The rate of spacing decrease is definitely dependent on the reaction temperature, being faster at higher temperatures. This spacing change represents ordering of opal-CT crystals with the passage of time.The relationship between thermal history and degree of ordering suggests that stratigraphic boundaries are usually parallel to isopleths of d (101) spacings, but do not always coincide with them. The isopleths should be more or less discordant to the stratigraphic boundaries where the strata have been folded. This discordancy can be ascribed to the difference of ordering, chiefly controlled by the thermal history during the burial and folding process.     

A pair of Langmuir cells in a laboratory tank (I) wind-only experiment

Three velocity components of subsurface flow, observed in a rectangular tank under the action of a constant wind speed, are measured systematically at mesh points distributed uniformly over a vertical cross-section of the tank. Measurements are carried out for two cases: 1) reference wind speedU _r =7.5 m/s and fetchF=10 m; and 2)U _r =10 m/s andF=25 m. A pair of Langmuir cells is observed for both cases; downwelling zones are found along both of the sidewalls and an upwelling zone in the centre of the tank. Near the water surface, the vertical momentum flux is dominated by the Reynolds stress resulting from small-scale turbulence, while over the entire cross-section except near the surface, the Reynolds stress due to the Langmuir cells dominates the vertical momentum flux. As the result of the occurrence of this Langmuir cells, the vertical momentum flux, which consists of both mean advection and small-scale turbulence, is markedly inhomogeneous in the spanwise direction; for example, the largest vertical flux of the order of the wind stress is observed in the downwelling zone near one sidewall, while at the centre of the tank, the vertical momentum flux occupies only 30% of the wind stress. This indicates that a pair of Langmuir cells plays more important role than small-scale turbulence in the mixing process in a greater part of the wind-wave tank.Address after April 1, 1992: Department of Civil Engineering, Hiroshima Institute of Technology, Miyake 2-1-1, Saeki-ku, Hiroshima 731-51, Japan.     

Monitoring the deep western boundary current in the western North Pacific by echo intensity measured with lowered acoustic Doppler current profiler

Oxidation of iron and manganese ions is predominant in the oxygen-rich deep western boundary current (DWBC) within the Pacific Ocean. By the faster removal of particulate iron hydroxide and manganese oxide, densities of the particulate matters are considered to be lower in the DWBC than the interior region. To detect the density variation of suspended particles between the DWBC and interior regions, we analyzed echo intensity (EI) measured in the western North Pacific by hydrographic casts with a 300 kHz lowered acoustic Doppler current profiler (LADCP) in a whole water column. At depths greater than 3000 m (~ 3000 dbar), EI is almost uniformly low between 12°N and 30°N but peaks sharply from 30°N to 35°N to a maximum north of 35°N. EI is found to be anomalously low in the DWBC compared to the background distribution. The DWBC pathways are identifiable by the low EI and high dissolved oxygen concentration. EI data by LADCPs and other acoustic instruments may be used to observe the temporal variations of the DWBC pathways.

     

Measurements of east Tushima Current in winter and estimation of its seasonal variability

The Tushima Current in the east channel was measured in a site of the strong current between Tushima and Iki Islands for 43 days of the winter in 1986. The primary results are:First, it was highly barotropic and flowed northeastward with a mean speed of about 20 cm sec^–1. Second, it was decelerated by northeast winds rather than by northwest winds in a frequency range of 0.3 and 0.4 cpd. Third, the scale analysis showed that the Tushima Current is approximately in geostrophic balance. The best empirical relationship between the measured Tushima Current and cross-channel adjusted sea level difference is given by