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261.
西北地区气溶胶光学特性及辐射影响 总被引:3,自引:1,他引:2
利用SACOL(兰州大学半干旱气候与环境观测站)2006~2012年AERONET(全球气溶胶自动监测网)level 2.0和太阳短波辐射计资料,分析了中国西北地区气溶胶的光学特性与辐射影响。利用辐射传输模式SBDART(平面平行大气辐射传输模式)检验TOA(大气层顶)处辐射强迫为正的原因。BOA(地表)、TOA、Atmosphere(大气)的辐射强迫年均值分别是-59.43 W m-2、-17.03 W m-2、42.40 W m-2,AOD(光学厚度,550 nm)年均值0.37,α(波段的波长指数,440~675 nm)年均值0.91,变化趋势与AOD位相相反,当AOD为0.3~2.2时,α很小(0.0~0.2),表明粒子尺度很大。SSA(单次散射反照率,675 nm)年均值0.93,g(不对称因子,675 nm)年均值0.68,复折射指数(675 nm)实部年均值1.48,虚部0.007。复折射指数实部的年变化趋势与AOD一致,虚部与AOD反位相,所以西北地区多为粗模态散射性气溶胶。气溶胶对大气的加热率最大值出现在0~2 km,随高度递减。冬、夏半年在地表加热率分别是2.6 K d-1和0.6 K d-1;季节变化中,冬季、秋季、春季和夏季,在地表的加热率依次是2.5 K d-1、1.4 K d-1、1.2 K d-1和0.2 K d-1,主要因为秋季气溶胶的吸收性大于春季。地表反照率和SSA对TOA正辐射强迫贡献率分别是22.5%和77.5%。 相似文献
262.
北京市水资源与水量平衡研究 总被引:4,自引:1,他引:3
以降雨-径流-蒸散发平衡和水资源供需平衡模式为基础进行研究,得到以下结论:北京市2001~2009年系列的水资源量与多年平均系列相比,水资源产量减少了约40.1%,减少的原因既有气候因素,也有人类活动导致土地覆被变化的原因,其中气候因素占30.1%,下垫面变化导致产流减少的比重为69.9%;同时由于人口的增长,北京市人均水资源占有量从270 m3下降到114 m3.在北京市水平衡分析中,采用不同下垫面蒸散发模式,计算得到2001~2009年北京市蒸散发为494 mm,河川径流量为46 mm,入境水量为4.34 亿m3,出境水量为8.03 亿m3,超采地下水、水库净补给以及外流域引水量为6.19 亿m3.在不考虑河道内生态需水条件下,北京市的现状缺水量为4.73~5.86 亿m3.到2014年南水北调中线水到达北京以后,北京将可以在75%来水年份下保障10~15年的水资源的基本供需平衡。但是如果遭遇95%来水频率的特枯年份,北京仍然将会面临较为严重的水资源短缺问题。 相似文献
263.
主被动微波遥感的探测技术是当前获取月壤厚度信息的重要手段。主动微波技术和被动微波技术在探测月壤厚度的物理机理、研究中使用的参数和考虑的关键问题等方面都有所不同。在总结了前人研究成果的基础上,系统分析了月壤厚度研究中需要着重考虑的参数分布,并详细探讨了主被动微波遥感技术获取月壤厚度的原理及研究中所涉及的关键问题。 相似文献
264.
Giacomo Corti Marco Bonini Francesco Mazzarini Mario Boccaletti Fabrizio Innocenti Piero Manetti Genene Mulugeta Dimitrios Sokoutis 《Tectonophysics》2002,348(4)
Scaled centrifuge experiments have been used to investigate the dynamic relations between deformation and magma distribution in rift-related transfer zones. The physical models were built using suitable analogue materials, such as sand to represent the brittle upper crust, various kinds of silicone mixtures to simulate the lower crust and upper mantle and glycerol to reproduce magma. Models simulated the development of transfer zones across pre-existing glycerol reservoirs placed at the base of the analogue continental crust. In plan view, different geometries, dimensions and positions of subcrustal reservoirs were reproduced in three different sets of experiments; to compare results, models were also performed without magma-simulating glycerol.Set 1 experiments, incorporating a narrow rectangular glycerol reservoir, show that the low-viscosity material is able to localise deformation into the overlying crust, giving rise to discrete transfer zones. This concentrated surface deformation corresponds at depth to major magma accumulation. Set 2 experiments, with an initial wide squared glycerol reservoir, show instead that deformation is distributed across the whole model surface, corresponding at depth to relatively minor magma accumulation. Set 3 experiments explored various positions of a small squared reservoir that invariably localised faulting in the overlying analogue brittle crust at the onset of model deformation.The overall model behaviour suggests that magma distribution at depth can effectively control the strain distribution in the overlying crust and the deformative pattern of transfer zones. Strain distribution, in turn, may control magma emplacement as localized deformation would favour major accumulation of magma at transfer zones. Coupled to a strong thermal weakening of the country rocks, this process may ultimately lead to a positive feedback interaction between magma and deformation. 相似文献
265.
南水北调西线调水工程区的自然生态环境评价 总被引:26,自引:0,他引:26
应用遥感与地理信息系统方法,对南水北调西线调水工程区遥感数据、地理信息数据进行一系列的信息识别、信息提取,获取了工程区地形地势、土地覆盖、植被覆盖度、植被净初级生产力、年均温度和年降雨量等主要的自然环境因子。用海拔高度反映地势状况,土地覆盖类型反映地表覆盖状况,植被覆盖度反映抗侵蚀能力,植被净生产力反映物质能量的循环状况,年均温度反映热量状况,年降水量反映降水状况,建立综合自然环境指数,对调水工程区的自然生态环境现状进行定量评价。按计算结果将调水工程区分为四级区域,并对这四级区域进行空间统计,分析了它们的自然生态环境,为全面深入进行南水北调西线工程区环境影响评价提供可供借鉴的新思路和新方法。 相似文献
266.
Field work in the South-Central Pyrenees suggests that omission contacts (i.e. younger over older rocks) occur at the base
of the Cadí unit (Cadí thrust), and pass laterally into thrusts. This change occurs across tear faults which are present in
the hangingwall of the Cadí thrust sheet and which controlled the deposition of Upper Cretaceous sediments (Adraén formation).
Detailed mapping in the contact area between the Nogueres and Cadí units has shown that the actual thrust geometry in the
study area is controlled by preexisting normal and transfer faults which developed in an already compressional context. Lateral
ramps or tear faults develop depending on the angle between the pre-existing extensional transfer fault and the thrust transport
direction. 相似文献
267.
Transferofmanganeseandferroionsbymanganesebacteria¥ShiJunxianandChenZhongyuan(TheSecondinstituteofOceanography,StateOceanicAd... 相似文献
268.
Based on the classical Boussinesq model by Peregrine [Peregrine, D.H., 1967. Long waves on a beach. J. Fluid Mech. 27 (4), 815–827], two parameters are introduced to improve dispersion and linear shoaling characteristics. The higher order non-linear terms are added to the modified Boussinesq equations. The non-linearity of the Boussinesq model is analyzed. A parameter related to h/L0 is used to improve the quadratic transfer function in relatively deep water. Since the dispersion characteristic of the modified Boussinesq equations with two parameters is only equal to the second-order Padé expansion of the linear dispersion relation, further improvement is done by introducing a new velocity vector to replace the depth-averaged one in the modified Boussinesq equations. The dispersion characteristic of the further modified Boussinesq equations is accurate to the fourth-order Padé approximation of the linear dispersion relation. Compared to the modified Boussinesq equations, the accuracy of quadratic transfer functions is improved and the shoaling characteristic of the equations has higher accuracy from shallow water to deep water. 相似文献
269.
The contribution of bound-free and free-free processes to the outward acceleration of Pup is studied and is found to be negligible. 相似文献
270.
Véronique Bommier 《Solar physics》1996,164(1-2):29-47
A synthesis work about the interaction of matter with polarized radiation, applied to solar magnetic field diagnostics, has recently been done by Stenflo (1994). This synthesis uses the classical theory of matter-radiation interaction - supplemented by the theory of partial redistribution of Omont, Smith, and Cooper (1972), on the one hand, and full quantum matter-radiation interaction theory, unable to take into account the partial frequency redistribution effects, on the other hand. The need of a full quantum approach taking into account the partial frequency redistribution effects appears as a unifying purpose; the present work, using the density matrix formalism, is a first attempt in this direction. 相似文献