非球形冰晶的毫米波k-Z_e关系研究   总被引：1，自引：0，他引：1  

吴举秀  魏鸣  周杰 《遥感学报》2013,17(6):1377-1395

针对毫米波雷达处理数据的实际需要,应用离散偶极子近似法DDA,获得了非球形冰晶的后向散射及衰减截面并进行了参数化,并主要基于细化的冰云模型,假设冰晶粒子谱为Γ分布,通过模拟取样各1330次（代表1330种粒子分布）,分别计算得到了W波段（94 GHz）与Ka波段（35 GHz）毫米波雷达探测的冰云衰减系数k及雷达反射率因子Z_e,而且利用数值模拟的方法,建立了k-Z_e关系的具体表达式。计算表明,非球形和非瑞利散射对W波段毫米波雷达衰减的影响较大,而且在同样滴谱分布条件下,W波段毫米波雷达的衰减比Ka波段毫米波雷达的大几倍,此外细化的冰云模型对k-Z_e关系具有影响。本研究对中纬度非降水性冰云的毫米波雷达的衰减订正具有参考价值,并对中国的毫米波雷达应用具有借鉴作用。  相似文献   

Mechanism of Anelasticity     

Fred Schwab 《Geophysical Journal International》1988,95(2):261-284

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鲁西峄山花岗岩中粗大钾长石斑晶成因探讨     

仲卫国  王聿军  臧学农  董作森 《山东国土资源》2005,(Z1)

在鲁西地区新太古代晚期(五台期)峄山花岗岩的黑石查和望子山花岗质岩体的岩石中,钾长石粗大斑晶内有自形程度较高的斜长石等矿物包裹体沿其环带定向排列。根据野外观察及岩石、矿物学特征测试分析,钾长石斑晶属于岩浆结晶形成的原生斑晶,受化学成分及侵位结晶过程中的物理化学条件影响,钾长石的生长速度大于其成核密度,因而形成粗大斑晶。估算岩浆温度>950℃,钾长石斑晶快速生长时岩浆温度为750℃,过冷度ΔT≈150℃,基质结晶时岩浆温度为600℃,ΔT≈300℃。  相似文献   

北极生长的多年海冰晶体结构分析   总被引：2，自引：4，他引：2  

李志军  康建成 《冰川冻土》2001,23(4):383-388

对中国首次北极科学考察钻取的一根从表面到底面长2.2m的海冰冰芯样，依据冰芯样采取时造成的长度，不等间距地自上而下垂直切片，剖析了冰芯样的晶体结构，获得以纯热力学生长为主的多年海冰正交偏光镜下晶体结构剖面，由晶体结构剖面确定出该海冰为三年冰，此外，还发现北极海冰越夏过程中生成一种动力碎屑凝聚冰，除给出偏光镜下晶体结构和冰芯层理分析外，还描述了动力碎屑凝聚冰的结构特点。  相似文献   

冰晶核化对雷暴云闪电行为影响的数值模拟研究     

谭涌波  向春燕  马肖  夏艳羚  张鑫 《气象学报》2017,75(2):328-341

为了探讨冰晶核化对雷暴云闪电行为的影响,通过已有的三维对流云起、放电模式探讨对比了3种冰晶核化方案,分别为原模式中的经验公式YS方案及与气溶胶相关的DE方案和LP方案。研究表明冰晶核化方案对雷暴云内冰晶微物理发展特征、起电及放电过程均有一定影响。模拟结果显示:(1)考虑了气溶胶的两种新参数化方案中冰晶粒子在高温区(高于-13.8℃)出现,在雷暴云发展过程中DE方案和LP方案冰晶的垂直分布均大于YS方案。(2)DE方案和LP方案中高温区出现的冰晶所带电荷极性有明显的反转现象,导致雷暴云电荷结构产生差异;雷暴云发展旺盛时刻DE方案和LP方案出现三级性电荷结构,而YS方案在整个雷暴云过程都是偶极性,并且DE方案和LP方案中电荷空间分布区域更加广泛。(3)不同核化方案下雷暴云放电特征存在差异,YS方案在偶极性电荷结构背景下没有负地闪产生,而DE方案和LP方案中次正电荷区的存在促进了负地闪的发生,并且负先导出现在较低的高度范围内;DE方案和LP方案中电荷量级较大,因此云闪发生频次以及正、负先导传播次数增加明显。  相似文献   

Modulations in incommensurate (Ca1–xSrx)2MgSi2O7 single crystals     

J. C. Jiang  M. Schosnig  A. K. Schaper  K. Ganster  H. Rager  L. Tóth 《Physics and Chemistry of Minerals》1998,26(2):128-134

Single crystals of (Ca_1–xSr_x)₂MgSi₂O₇ slightly doped with 1000 ppm Mn²⁺ and with x ranging from 0.04 to 0.32 were grown from the melt in a mirror furnace applying the Czochalski technique. Transmission electron microscopy (TEM) revealed incommensurately modulated structures at room-temperature for all compositions in accordance with earlier studies by electron paramagnetic resonance (EPR). Electron diffraction patterns clearly show satellite reflections typical for two-dimensional modulation, and their successive destabilization with increasing Sr content. The modulation is of tartan-like appearance. Beyond a Sr/(Sr+Ca) ratio of about 0.32 the synthesis of stable solid solution åkermanite type crystals was proved not to be feasible, indicating the existence of a miscibility gap in the Sr åkermanite system. As presumed from the diffuse scattering around the satellite reflections, and suggested more conclusively by crystallographic processing of high resolution EM images the Sr ions incorporated into the incommensurate crystal phase are distributed in an ordered fashion and are partly adapted to the displacive modulation of the pure åkermanite. This means, occupational modulation even makes a contribution to the overall modulation characteristics in (Ca_1–xSr_x)₂ MgSi₂O₇.  相似文献   

On the hydrodynamic behavior of supercooled water drops interacting with columnar ice crystals     

R. J. Schlamp  H. R. Pruppacher 《Pure and Applied Geophysics》1977,115(4):805-843

A numerical evaluation of the complete Navier-Stokes equations of motion for steady-state, incompressible flow past an infinite circular cylinder is given in terms of the stream function, vorticity, and pressure distribution past such bodies. A method is described which allows use of these flow characteristics: (1) to approximate the characteristics of air flow past hexagonal columnar ice crystals falling under gravity at terminal velocity in air, (2) to compute the trajectory of supercooled cloud drops relative to such ice crystals, and (3) to determine the efficiency with which short columnar ice crystals and needle shaped ice crystals collide with supercooled cloud drops. It is found that for all columnar type ice crystals riming is negligible if the cloud drop size is less than 5 m, and that for riming to commence short columnar crystals must have diameters larger than 50 m, while needle crystals must have diameters larger than 40 m. It is further shown that the collision efficiency cut-offs at the small drop radius and at the large drop radius end of the collision efficiency diagram can be explained on the basis of the cloud drop trajectories for these drop size ranges.  相似文献   

On the efficiency with which aerosol particles of radius less than 1 μm are collected by columnar ice crystals     

P. K. Wang  H. R. Pruppacher 《Pure and Applied Geophysics》1980,118(2):1090-1108

A theoretical model is presented which allows computing the efficiency with which aerosol particles of 0.001 r1 m are collected by columnar ice crystals in air of various relative humidities, temperatures, and pressures. Particle capture due to Brownian diffusion, thermo- and diffusiophoresis is considered. It is shown that phoretic effects importantly determine the particle capture process of 0.01r1 m. The various pressure-temperature levels studied are found to affect the collection efficiency only ifr>0.1 m. Comparison shows that water drops generally are better aerosol particle scavengers than columnar ice crystals.  相似文献   

贵州夏季自然云中冰雪晶和大粒子观测结果的分析     

杨平 《高原气象》1988,(2)

本文对夏季贵州自然降水性云的冰雪晶、大粒子作了初步分析。主要结果有:(1)冰雪晶平均浓度比北方地区的低,另外云中含水量大的区域冰雪晶平均浓度值也较大。(2)积状云冰雪晶浓度频数分布较集中,大多数集中于平均值附近,不超过一个量级。(3)冰雪晶和大粒子空间分布有明显差异。(4)在浓积云内暖云部分有冰雪晶沉降。(5)贵州夏季自然云降水及其人工催化的研究必须考虑冰相过程。  相似文献   

Late Mesozoic low-P/high-T metamorphism preceding emplacement of Cretaceous granitic rocks in the Gosaisho-Takanuki district, Abukuma metamorphic belt     

Michio  Tagiri Hitoshi  Sato Eiji  Matsumura Hiroyuki  Nemoto 《Island Arc》1993,2(3):152-169

Abstract The central part of Abukuma metamorphic belt consists of two geologic units, the Gosaisho Group and the Takanuki Group. Although the deformation styles differ between the Gosaisho and the Takanuki Groups, their rock facies show a gradual transition. In both Groups early regional low-pressure (over 3 kb) metamorphism has been overprinted by contact metamorphism. Evidence for the P/T condition of the regional metamorphism is recorded in cores of armored minerals. Metamorphic zones have been defined on mineral rim assemblages of meta-mafite, meta-pelite and meta-calc-siliceous schist and on the degree of graphitization of meta-pelite. The mineral-core chemistry of plagioclase, Ca-amphibole and garnet changes with increasing metamorphic grade, and indicates that the regional metamorphism of the Gosaisho Group took place in a high pressure region of the andalusite stability field. The Takanuki metamorphic rocks are structurally overlain by the Gosaisho Group and have undergone regional metamorphism whose conditions have passed near the triple point of Al-silicates and kyanite has crystallized. The contact aureoles in both groups are developed around middle Cretaceous granitic intrusions. Rims of plagioclase, Ca-amphibole and garnet overgrew on the mineral-cores during the contact metamorphism. The regional metamorphism began after the sedimentation of Jurassic chert and was succeeded by the contact metamorphism in the middle Cretaceous.  相似文献