Net Energy Payback and CO2 Emissions from Three Midwestern Wind Farms: An Update

This paper updates a life-cycle net energy analysis and carbon dioxide emissions analysis of three Midwestern utility-scale wind systems. Both the Energy Payback Ratio (EPR) and CO₂ analysis results provide useful data for policy discussions regarding an efficient and low-carbon energy mix. The EPR is the amount of electrical energy produced for the lifetime of the power plant divided by the total amount of energy required to procure and transport the materials, build, operate, and decommission the power plants. The CO₂ analysis for each power plant was calculated from the life-cycle energy input data. A previous study also analyzed coal and nuclear fission power plants. At the time of that study, two of the three wind systems had less than a full year of generation data to project the life-cycle energy production. This study updates the analysis of three wind systems with an additional four to eight years of operating data. The EPR for the utility-scale wind systems ranges from a low of 11 for a two-turbine system in Wisconsin to 28 for a 143-turbine system in southwestern Minnesota. The EPR is 11 for coal, 25 for fission with gas centrifuge enriched uranium and 7 for gaseous diffusion enriched uranium. The normalized CO₂ emissions, in tonnes of CO₂ per GW_eh, ranges from 14 to 33 for the wind systems, 974 for coal, and 10 and 34 for nuclear fission using gas centrifuge and gaseous diffusion enriched uranium, respectively.     

Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 1: Hydrological Conditions and Dust Flux

The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition. Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3) sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric dust concentration over Northeast China in the last 220 years.     

Ice draft and current measurements from the north-western Barents Sea, 1993–96

From 1993 to 1996, three oceanographic moorings were deployed in the north-western Barents Sea, each with a current meter and an upward-looking sonar for measuring ice drafts. These yielded three years of currents and two years of ice draft measurements. An interannual variability of almost I m was measured in the average ice draft. Causes for this variability are explored, particularly its possible connection to changes in atmospheric circulation patterns. We found that the flow of Northern Barents Atlantic-derived Water and the transport of ice from the Central Arctic into the Barents Sea appears to be controlled by winds between Nordaustlandet and Franz Josef Land, which in turn may be influenced by larger-scale variations such as the Arctic Oscillation/North Atlantic Oscillation.     

A subduction wedge origin for Paleoarchean peridotitic diamonds and harzburgites from the Panda kimberlite, Slave craton: evidence from Re–Os isotope systematics

An extensive study of peridotitic sulfide inclusion bearing diamonds and their prospective harzburgitic host rocks from the 53 Ma Panda kimberlite pipe, Ekati Mine, NWT Canada, has been undertaken with the Re–Os system to establish their age and petrogenesis. Diamonds with peridotitic sulfide inclusions have poorly aggregated nitrogen (<30% N as B centers) at N contents of 200–800 ppm which differs from that of chromite and silicate bearing diamonds and indicates residence in the cooler portion of the Slave craton lithospheric mantle. For most of the sulfide inclusions, relatively low Re contents (average 0.457 ppm) and high Os contents (average 339 ppm) lead to extremely low ¹⁸⁷Re/¹⁸⁸Os, typically << 0.05. An age of 3.52 ± 0.17 Ga (MSWD = 0.46) and a precise initial ¹⁸⁷Os/¹⁸⁸Os of 0.1093 ± 0.0001 are given by a single regression of 11 inclusions from five diamonds that individually provide coincident internal isochrons. This initial Os isotopic composition is 6% enriched in ¹⁸⁷Os over 3.5 Ga chondritic or primitive mantle. Sulfide inclusions with less radiogenic initial Os isotopic compositions reflect isotopic heterogeneity in diamond forming fluids. The harzburgites have even lower initial ¹⁸⁷Os/¹⁸⁸Os than the sulfide inclusions, some approaching the isotopic composition of 3.5 Ga chondritic mantle. In several cases isotopically distinct sulfides occur in different growth zones of the same diamond. This supports a model where C–O–H–S fluids carrying a radiogenic Os signature were introduced into depleted harzburgite and produced diamonds containing sulfides conforming to the 3.5 Ga isochron. Reaction of this fluid with harzburgite led to diamonds with less radiogenic inclusions while elevating the Os isotope ratios of some harzburgites. Subduction is a viable way of introducing such fluids. This implies a role for subduction in creating early continental nuclei at 3.5 Ga and generating peridotitic diamonds.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Evaluation of three waterborne polymers as stabilizers for sandy soil

This study reports on waterborne polymer emulsion systems that were used for structural modification of sandy soils. The first emulsion used was a styrene-acrylic, copolymer emulsion; the second and third were vinyl-acrylic, copolymer-based emulsions. Specimens were prepared by adding different polymer emulsions to the sand and water in prescribed amounts. The performance of the different emulsion systems as sand stabilizers was estimated through measurement of the hydraulic conductivity and compressive strength. Measurements of hydraulic conductivity were conducted in a flexible membrane test apparatus. The hydraulic conductivity for the three emulsions decreased at different rates, with an increase in polymer content up to 3 wt. (i.e., % by weight). Additional increase of polymer content did not introduce significant decrease in hydraulic conductivity, and, at 5 wt.%, the three emulsions had essentially the same effect. Measurements made on dry cylindrical specimens disclosed remarkable enhancement in the mechanical behavior of the system. The compressive strength and modulus of elasticity of the examined emulsions increased with a higher concentration of polymer. Scanning electron microscope (SEM) revealed that the reduction in the permeability and the improved mechanical properties can be attributed to three dominant structural changes: the development of interconnecting ties between the sand particles, the development of adhesion between neighboring sand particles in contact, and the covering of the sand particles with a thin polymer film.     

地下圆形衬砌隧道对沿线地震动的影响(II):数值结果

利用地下圆形衬砌隧道对入射平面P波和SV波散射级数解答，定量分析了入射波长、入射角度、隧道直径、衬砌刚度等因素对沿线地表位移放大作用的影响。计算结果表明，当入射频率较低时，地下隧道的存在对地表位移幅值影响不大；而当入射频率较高时，地表位移幅值可以达到无隧道情况的4．5倍以上；衬砌情况下地表位移幅值可以高出非衬砌情况的87．8％。建议在地铁的规划设计中考虑地下隧道的建设对隧道沿线设计地震动的影响。     

Spaceborne gravitational field determination by means of locally supported wavelets

In space-borne gravitational field determination, two challenges are inherent. First, the continuation of the data down to the surface of the Earth is an ill-posed problem, requiring therefore regularization techniques. Second huge data sets result requiring efficient numerical methods. In this paper, we show how locally supported wavelets on the sphere can be developed by means of a spherical version of the so-called up function. By construction, the corresponding scaling functions and wavelets are infinitely smooth, so that they can be used for regularization purposes. In particular, we show how the ill-posed pseudo-differential equations coming from satellite missions can be regularized by efficient numerical schemes using locally supported wavelets. These methods seem in particular to be interesting for regional gravity field modelling.     

Comparison of ERS-SAR and spot data for sugar beet crop cover assessment

The present work was aimed to compare the abilities of radar and optical satellite data to estimate crop canopy cover, which is a key component of productivity estimates. Three ERS-1 SAR images were obtained of East Anglia (UK) in 1995 and one ERS-2 SAR image in 1996. The images covered a study area around the IACR Brooms Barn Sugar Beet Research Institute. Field data comprising radiometric and biophysical measurements of the crop canopy were collected in two fields from June 22 to August 3, 1995 to coincide with ERS-1 SAR overpass dates. In 1996, field data were collected in two fields from June 11 to July 29 on a weekly basis. A previously calibrated version of the water cloud model was inverted to estimate Leaf Area Index (LAI) from ERS-1 and ERS-2 SAR backscatter and soil moisture samples. Canopy cover was estimated from the radar-estimated LAI using a standard exponential relationship that has a well-established coefficient for sugar beet. Radio-metrically and atmospherically corrected data from three SPOT images in 1995 and one SPOT image in 1996 were used to calculate the Optimised Soil Adjusted Vegetation Index (OSAVI), from which crop canopy cover was estimated using a relationship determined previously by canopy modelling. The crop cover values estimated by satellite were in good agreement with those measured on ground with the Parkinson radiometer. Radar data may be able to provide useful estimates of canopy cover for crop production modelling, especially in the case of loss of optical data due to cloud.     

Distribution of seasonal rainfall in the East Asian monsoon region

Summary ?This study deals with the climatological aspect of seasonal rainfall distribution in the East Asian monsoon region, which includes China, Korea and Japan. Rainfall patterns in these three countries have been investigated, but little attention has been paid to the linkages between them. This paper has contributed to the understanding of the inter-linkage of various sub-regions. Three datasets are used. One consists of several hundred gauges from China and South Korea. The second is based on the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP). The two sources of precipitation information are found to be consistent. The third dataset is the NCEP/NCAR reanalysis 850-hPa winds. The CMAP precipitation shows that the seasonal transition over East Asia from the boreal winter to the boreal summer monsoon component occurs abruptly in mid-May. From late March to early May, the spring rainy season usually appears over South China and the East China Sea, but it is not so pronounced in Japan. The summer monsoon rainy season over East Asia commonly begins from mid-May to late May along longitudes of eastern China, the Korean Peninsula, and Japan. A strong quasi-20-day sub-seasonal oscillation in the precipitation appears to be dominant during this rainy season. The end date of the summer monsoon rainy season in eastern China and Japan occurs in late July, while the end date in the Korean Peninsula is around early August. The autumn rainy season in the Korean Peninsula has a major range from mid-August to mid-September. In southern China, the autumn rainy season prevails from late August to mid-October but a short autumn rainy season from late August to early September is noted in the lower part of the Yangtze River. In Japan, the autumn rainy season is relatively longer from mid-September to late October. The sub-seasonal rainfall oscillation in Korea, eastern China and Japan are explained by, and comparable to, the 850-hPa circulation. The strong westerly frontal zone can control the location of the Meiyu, the Changma, and the Baiu in East Asia. The reason that the seasonal sea surface temperature change in the northwestern Pacific plays a critical role in the northward advance of the onset of the summer monsoon rainfall over East Asia is also discussed. Received October 5, 2001; revised April 23, 2002; accepted May 11, 2002