中国东部地区SO₂, SO₄⁼和HNO₃(g)干沉降速度的季节变化   总被引：5，自引：0，他引：5  

毛节泰  李建国 《气象学报》1997,55(5):545-562

使用中国东部及其邻近地区各主要台站１９９２年全年００点和１２点（ＧＭＴ）地面及探空资料，由中尺度气象预报模式ＭＭ４产生中国东部地区地面以上大约４０ｍ高度（最低模式层）处二维温度、湿度和风场，使用污染物干沉降模块及该地区下垫面类型资料，计算出了该地区ＳＯ２，ＳＯ＝４和ＨＮＯ３（ｇ）全年干沉降速度的区域分布和季节变化。结果表明，由于受气象条件和下垫面类型的综合影响，３种污染物的干沉降速度有明显的变化。对ＳＯ２，全年区域平均极小值为０．０８８ｃｍ／ｓ，极大值为１．２７５ｃｍ／ｓ，平均值为０．４３０ｃｍ／ｓ；对ＳＯ＝４，分别为０．０１４ｃｍ／ｓ，０．２８７ｃｍ／ｓ和０．１１８ｃｍ／ｓ；对ＨＮＯ３（ｇ），分别为０．０６０ｃｍ／ｓ，５．２５０ｃｍ／ｓ和１．１２３ｃｍ／ｓ。ＳＯ２干沉降速度极大值分布在巴丹吉林沙漠和腾格里沙漠一带，对ＳＯ＝４和ＨＮＯ３（ｇ），除在上述沙漠地带有一极大值区域外，在靠近四川的云贵高原尚有另一极大区。对１９９２年全年来说，ＳＯ２和ＨＮＯ３（ｇ）干沉降速度极大值均出现在七月份，分别为０．５５２ｃｍ／ｓ和１．５１８ｃｍ／ｓ；而对ＳＯ＝４，干沉降速度极大值出现在九月份，其值为０．０９６ｃｍ／ｓ。这些值  相似文献   

冲积床面阻力关系分析比较          下载免费PDF全文

王士强 《水科学进展》1993,4(2):113-119

进一步验证和分析了作者早先提出的动床阻力关系,总结并提出了新的沙垄高度变化规律图,分析了它们与沙波阻力变化的关系,比较系统地揭示了不同水深、粒径条件下过渡区阻力变化规律.文中比较了作者及国内外其它五个重要的动床阻力关系,明确了这些公式的适用范围及限制条件.Einstein和钱宁的二个阻力关系只能用于过渡区,且后者只适用于粉细沙河床.李昌华的阻力关系可用于过渡区及低能态区.Engelund的阻力关系可用于一般沙质河床的低能态和高能态条件,但缺乏过渡区规律,对粉沙河床预报将系统偏小而对沙卵石河床则反之.Hayashi的阻力关系不适用于比降平缓的平原沙质河流.经验证和比较,作者的阻力公式适用于三个能态区各种水流强度及不同水深、粒径的情况,适用范围广泛,预报精度较高.  相似文献   

Rock resistance to erosion: Some further considerations     

Paul C. Augustinus 《地球表面变化过程与地形》1991,16(6):563-569

Rock resistance to erosion is an often described factor in geomorphic studies, and is generally considered to strongly influence the shape of erosional landforms. However, the property of the rock mass that enables it to resist erosion is rarely considered, and its measurement is rarely justified and assessed adequately. Allison (1988, 1990) examined the intact strength properties of several types of carbonate rocks and considered that dynamic Young's modulus is a good indicator of rock material strength for geomorphic purposes, and cast doubts on the reliability of Schmidt hammer tests for this purpose. Alternative approaches to rock characterization from the view point of evaluating rock intact strength are considered.  相似文献   

Time-dependency of runoff velocity and erosion the effect of the initial soil moisture profile   总被引：1，自引：0，他引：1  

Gerard Govers 《地球表面变化过程与地形》1991,16(8):713-729

The paper reports on experiments carried out to evaluate the effect of the initial soil moisture profile on temporal variations in runoff erosion rate. The moisture profile was varied by applying infrared heating to the soil sample surface over various time periods, while runoff erosivity was varied by varying the slope of the flume. The experiment confirms that dry loamy soils are very erodible: on a slope length of only 4.3 m long sediment concentrations are near transporting capacity in case of a dry soil sample. It appears that temporal variations in sediment concentrations can be well simulated using a simple relationship between runoff erosion resistance and initial soil moisture content, thereby implicitly assuming that the effect of initial moisture content is persistent over the whole duration of the experiment. The implications of these findings with respect to the modelling of sediment output from larger catchments and the design of experiments on rill erodibility are discussed. The experiments also show that, under the present circumstances, mean velocities in the rills appear to be independent of slope. This finding may be of importance with respect to overland flow routing and deterministic erosion modelling.  相似文献   

On the stability of the geostatistical method     

Noel Cressie  Dale L. Zimmerman 《Mathematical Geology》1992,24(1):45-59

A thorough geostatistical analysis of spatial data, observed at given spatial locations, includes exploratory data analysis, spatial-model building, diagnosing the model fit, and inference on unknown model parameters or unobserved values (at known locations). Using results from mathematical analysis, exact and asymptotic distribution theory, and simulation studies, we argue that, when used sensibly, the geostatistical method is reassuringly stable.  相似文献   

通风参数计算的灰色建模法     

张国屏  赵云胜 《地球科学》1988,(4)

本文根据灰色建模理论,提出灰色模型群建模法。其实质是利用计算机,对一系列预报模型进行比较,输出了个最优模型。文中通风管流参数计算的灰色建模结果令人满意,说明灰色建模理论在实验数据处理中是一个有力工具。  相似文献   

Resistance to flow past deformable boundaries     

T. R. Davies  A. J. Sutherland 《地球表面变化过程与地形》1980,5(2):175-179

An hypothesis from which a general principle covering deformation of alluvial boundaries may be developed is proposed, namely—flow of fluid past a deformable boundary will deform the boundary so as to increase the resistance to flow. Upon attainment of a local maximum of resistance to flow the boundary shape will cease to change. Evidence from channel bed forms, meander geometry and armoured beds is presented to support the hypothesis. One implication of the hypothesis is that channels will adjust so that sediment movement is maximized. The authors would like geomorphologists to test this in their work on landscape evolution.  相似文献   

Characteristics of multiple-fan ventilation networks   总被引：1，自引：0，他引：1  

Y. J. Wang 《Geotechnical and Geological Engineering》1984,2(3):229-243

Summary The definitions of system pressure loss (mine head) and system resistance, which are traditionally associated with single-fan networks, are applied to multiple-fan ventilation networks. The system characteristics, relations among air power, pressure loss, air quantity and resistance, are analysed by introducing the concept of subsystems. These subsystems are associated with the fans located in a cutset of the network.For a multiple-fan network, the resistances for the subsystems and total system are dependent on the quantity ratios of the subsystems. In general the pressure loss of a subsystem or a total system does not vary as the square of the corresponding air quantity. If the quantity ratios of subsystems are all held constant, then the resistances become constant and the pressure losses are predictable from the quantities employing the square law. The system resistance has a minimum value under the natural-splitting flow pattern. Being independent of the value of system quantity, the minimum system resistance provides a basis for comparing the different networks.  相似文献   

山区卵砾石河道水流阻力计算          下载免费PDF全文

罗铭  黄尔  王协康  杨奉广 《水科学进展》2020,31(3):404-412

卵砾石河道广泛存在于山区河流中,在卵砾石河床近底层的水流流速低于上方流速,速度剖面出现拐点,类似于自由剪切流动,传统的指数型和对数型水流阻力公式计算误差偏大。将自由剪切流理论类比到山区卵砾石河道,并考虑山区河流特殊流态、流场和剪切力的影响,引入雷诺数(Re)、弗劳德数(Fr)和摩阻流速利用水槽数据进一步修正了该类水流阻力公式。筛选位于意大利南部的亚平宁山脉140条山区河流野外数据对新公式进行验证,并检验对比了已发表的多个山区河流阻力公式。结果表明:修正后的水流阻力公式Nash-Sutcliffe效率指数最接近1、均方根误差最小、相对误差最小。自由剪切流动的类比是从湍流结构角度推导河道水流阻力,能更好地阐释特殊水流结构,进而提高计算精度。  相似文献   

唐山抗震精神的形成和历史意义     

李贵  宗玉田 《国际地震动态》1996,(12):23-28

文章以丰富的第一手资料为依据，深刻地揭示唐山抗震精神产生的根源，提出中华民族的传统文化是抗震精神的直接思想来源，近代工业革命锤炼的唐山人是抗震精神的主体，伟大的抗震减灾斗争是抗震精神的实践基础，以此为基础，阐述了唐山抗震精神在抗震减灾中的作用历史意义。  相似文献