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61.
The development of the boundary layer during a cold air outbreak in the FramStrait is documented by aircraft measurements. The convection was organisedinto roll vortices with aspect ratios increasing from 2.9 near the ice edgeto more than 6 at 100 km further downstream. This increase coincides with anincrease of the latent heat release in the cloud layer. The stability parameter-zi/L varies from about zero at the ice edge to 30 at a distance of 200 kmdownstream over open water where the satellite picture still shows cloudstreets. The increase is mainly due to the deepening of the boundary layer.The turbulent vertical sensible and latent heat fluxes near the surface amountto 400 W m-2 within a 300 km off-ice zone. 25% of the upward heat fluxin the subcloud layer is carried out by organised roll motions. Experimentswith a 2-dimensional non-hydrostatic model show a similar roll aspect ratio inthe first 50 km, but further downstream where condensational heating is moreimportant the modelled roll wavelengths are distinctly smaller than the observedones. 相似文献
62.
红壤丘陵小区域水平上不同时段土壤质量变化的评价和分析 总被引:39,自引:1,他引:39
引相相对土壤质量指数的概念,应用地理信息系统技术,为小区域水平上土壤质量时空变化的评价提供了一种方法,并用于千烟洲试验站开垦利用11a后土壤质量变化的评价。统计分析服农田,桔园,牧草地,人工林,天然林等多种土地利用方式下土壤质量变化的特征。 相似文献
63.
介绍了利用GPS开展1:20万石棉幅区域重力测量的情况,对正确掌握GPS的工作方法作了研究,并总结了应用该项技术的成功经验和遗留问题。 相似文献
64.
DYNAMIC VARIATIONS OF WATER QUALITY IN TAIHU LAKE AND MULTIVARIATE ANALYSIS OF ITS INFLUENTIAL FACTORS 总被引:1,自引:0,他引:1
Cai Qiming Gao Xiyun Chen Yuwei Ma Shengwei Nanjing Institute of Geography Limnology CAS Nanjing People''s Republic of ChinaMartin Dokulil Institute of Limnology Austria 《地理学报(英文版)》1997,(3)
LakeTaihuisalargeshallowlakeinChina,whichpalysanimportantroleinwater-quantityregulation,watersupply,cultivationetc.Withrapiddevelopmentofagricultureandindustryinthearea,alargenumberofpollutantshavebeendischargedintothelake,leadingtoanincreaseinnutrients… 相似文献
65.
Water-quality trends in White Rock Creek Basin from 1912-1994 identified using sediment cores from White Rock Lake reservoir, Dallas, Texas 总被引:2,自引:0,他引:2
Historical trends in selected water-quality variables from 1912 to 1994 in White Rock Creek Basin were identified by dated sediment cores from White Rock Lake. White Rock Lake is a 4.4-km2 reservoir filled in 1912 and located on the north side of Dallas, Texas, with a drainage area of 259 km2. Agriculture dominated land use in White Rock Creek Basin before about 1950. By 1990, 72% of the basin was urban. Sediment cores were dated using cesium-137 and core lithology. Major element concentrations changed, and sedimentation rates and percentage of clay-sized particles in sediments decreased beginning in about 1952 in response to the change in land use. Lead concentrations, normalized with respect to aluminum, were six times larger in sediment deposited in about 1978 than in pre-1952 sediment. Following the introduction of unleaded gasoline in the 1970s, normalized lead concentrations in sediment declined and stabilized at about two and one-half times the pre-1952 level. Normalized zinc and arsenic concentrations increased 66 and 76%, respectively, from before 1952 to 1994. No organochlorine compounds were detected in sediments deposited prior to about 1940. Concentrations of polychlorinated biphenyls (PCB) and DDE (a metabolite of DDT) increased rapidly beginning in the 1940s and peaked in the 1960s at 21 and 20 µg kg-1, respectively, which is coincident with their peak use in the United States. Concentrations of both declined about an order of magnitude from the 1960s to the 1990s to 3.0 and 2.0 µg kg-1, respectively. Chlordane and dieldrin concentrations increased during the 1970s and 1980s. The largest chlordane concentration was 8.0 µg kg-1 and occurred in a sediment sample deposited in about 1990. The largest dieldrin concentration was 0.7 µg kg-1 and occurred in the most recent sample deposited in the early 1990s. Agricultural use of chlordane and dieldrin was restricted in the 1970s; however, both were used as termiticides, and urban use of chlordane continued at least until 1990. Recent use of dieldrin and aldrin, which degrades to dieldrin, has not been reported; however, increasing trends in dieldrin since the 1970s suggest recent urban use could have occurred. 相似文献
66.
张玉良 《华北地质矿产杂志》1996,11(2):237-244
本文对离柳矿区奥陶系灰岩岩溶地下水的环境质量进行了评价和分区,结合地质条件简述了各区的特点;还用地质-水文地质学相结合的理论,对各环境质量区形成的原因,进行了分析和研究,进而从理论上证明环境质量分区和选用标准的合理性。 相似文献
67.
The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but the impact is limited because of the dry climate and lack of runoff in that area. 相似文献
68.
介绍了安阳电厂冷却塔碎石桩复合地基静载、动力触探、瑞利波法系列原位试验。根据试验结果,对冷却塔地基加固与改良效果及施工质量进行了评价。 相似文献
69.
The identifiability of parameters in a water quality model of the Biebrza River, Poland 总被引:1,自引:0,他引:1
The identifiability of model parameters of a steady state water quality model of the Biebrza River and the resulting variation in model results was examined by applying the Monte Carlo method which combines calibration, identifiability analysis, uncertainty analysis, and sensitivity analysis. The water quality model simulates the steady state concentration profiles of chloride, phosphate, ammonium, and nitrate as a function of distance along a river. The water quality model with the best combination of parameter values simulates the observed concentrations very well. However, the range of possible modelled concentrations obtained for other more or less equally eligible combinations of parameter values is rather wide. This range in model outcomes reflects possible errors in the model parameters. Discrepancies between the range in model outcomes and the validation data set are only caused by errors in model structure, or (measurement) errors in boundary conditions or input variables. In this sense the validation procedure is a test of model capability, where the effects of calibration errors are filtered out. It is concluded that, despite some slight deviations between model outcome and observations, the model is successful in simulating the spatial pattern of nutrient concentrations in the Biebrza River. 相似文献
70.
R. M. Godinho M. C. Freitas H. Th. Wolterbeek 《Journal of Atmospheric Chemistry》2004,49(1-3):355-361
The present work evaluates the stress effects in two epiphytic lichen species with different thallus morphology, the foliose Parmelia caperata and the fruticose Evernia prunastri, as resulting from transplanting from an unpolluted to an air-polluted area. Lichen samples were collected in Portugal in a clean area, during the spring 2003, and transplanted (1) to the same zone nearby and (2) to a polluted area as affected by an industrial complex. Transplant samples were taken periodically during four months in both places. At the same time lichen samples from the clean-air site native (in-situ) populations were also collected. For each sample were measured the chlorophyll content, the chlorophyll degradation and the cell membrane damage, the latter represented by leacheate conductivity. During the experiment the meteorological conditions were registered. The results indicate the absence of stress effects of transplanting as such, and suggest that leachate conductivity may be the more sensitive indicator of general lichen vitality. 相似文献