应用全型散度方程诊断鄂东北一次梅雨强降雨

利用0.5°×0.5°GFS分析资料和常规气象观测资料,分析2013年7月5—7日鄂东北梅雨连续暴雨过程。结果表明:1降雨具有比较明显的日变化,夜间加强,白天减弱;鄂东北低层辐合也有与降雨强度一致的日变化特点。2散度变率在高层出现正值、中低层出现负值有利于降雨加强,且这种变化比暴雨发生稍有提前。一般傍晚散度变率在低层即出现负值,这有利于夜间低层辐合加强。3利用全型散度方程2项组合诊断发现,虽然非线性平衡方程偏差项确是散度变率的主要项,但在降雨开始阶段只有余项在低层出现较为明显的负值。4利用全型散度方程4项组合诊断发现,边界层水平风场辐合是降雨启动因子之一;非地转平衡项在近地面出现较大正值对于降雨减弱有较好的指示;与垂直运动有关的项在降雨峰值阶段中层负值较大。     

基于时间序列的地表温度反演:以松江河地区为例

为研究同一地区不同时相的地表温度受植被和地表状况等因素影响后,其温度变化程度的差异,以Landsat 5 TM和Landsat 7 ETM+热红外数据为数据源,采用辐射传输方程法分别反演了松江河地区12个不同月份的地表真实温度,并分析出现稳态温度异常地段的影响因素,计算12个月的温度反演结果的均值和方差。结果表明:1平均值图像中的温度异常区域与绝大部分时相图像的温度异常区域十分相似,图像西北区域和中心区域出现较多温度异常。2方差图像中原系列图像中高温异常的区域,其方差也较大,即时间序列上温度波动较大;原系列图像中植被覆盖度较高的区域,其方差较小,即时间序列上温度变化较为稳定。     

南海文昌地区内波振幅反演研究

The field experiment is conducted from April 16,2005 to July 20,2005 at Wenchang area east of Hainan Island(19°35'N,112°E) of China.Internal wave packets are observed frequently with thermistor chains during the experiment.Meanwhile,internal waves are also detected from a synthetic aperture radar(SAR) image on June 19,2005 and several other moderate-resolution imaging spectroradiometer(MODIS) images near a mooring position.The distance between the positive and negative peaks induced by the internal wave can be obtained from satellite images.Combined with remote sensing images and in situ data,a new method to inverse the amplitude of the internal wave is proposed based on a corrected nonlinear Schr?dinger(NLS) equation.Two relationships are given between the peak-to-peak distance and the characteristic wavelength of the internal wave for different nonlinear and dispersion coefficients.Based on the satellite images,the amplitude inversion of the internal waves are carried out with the NLS equation as well as the Kd V equation.The calculated amplitudes of the NLS equation are close to the observation amplitude which promise the NLS equation a reliable method.     

中国黄渤海沉积物声速与物理性质研究

In order to investigate the correlation between a sound velocity and sediment bulk properties and explore the influence of frequency dependence of the sound velocity on the prediction of the sediment properties by the sound velocity,a compressional wave velocity is measured at frequencies of 25–250 k Hz on marine sediment samples collected from the Bohai Sea and the Yellow Sea in laboratory,together with the geotechnical parameters of sediments.The results indicate that the sound velocity ranges from 1.232 to 1.721 km/s for the collected sediment samples with a significant dispersion within the series measuring frequency.Poorly sorted sediments are highly dispersive nearly with a positive linear relationship.The porosity shows a better negative logarithmic correlation with the sound velocity compared with other geotechnical parameters.Generally,the sound velocity increases with the increasing of the average particle size,sand content,wet and dry bulk densities,and decreasing of the clay content,and water content.An important point should be demonstrated that the higher correlation can be obtained when the measuring frequency is low within the frequency ranges from 25 to 250 k Hz since the inhomogeneity of sediment properties has a more remarkably influence on the laboratory sound velocity measurement at the high frequency.     

存在初始“传导盖层”的月球岩浆洋演化与月壳成因

月球早期经历了岩浆洋阶段,岩浆洋的研究对认识月球内部构造有着重要意义。月球岩浆洋演化主导模型认为:岩浆洋结晶到80%左右,斜长石开始结晶,并上浮形成斜长岩月壳。该模型与观察事实存在两点矛盾:1)基于该模型计算结晶的斜长石An牌号比高地样品斜长石An牌号测试结果低;2)该模型散热速率计算指示岩浆洋在几个百万年时间内固化,而同位素体系对月球岩石样品定年结果表明月壳的结晶年龄十分古老,并且结晶区间跨越了270Myr,这与主导模型之间存在矛盾。以解决以上两点矛盾为目的,本文论证岩浆洋在演化之初硕部存在冷却"盖层",并将硅酸盐熔体在温度梯度下的热扩散效应引入岩浆洋演化模型。热扩散效应指均一的物质在温度梯度下发生分异的过程。本文工作模型是:由于月球的重力常数小,不能有效的保持大气,因此月球的岩浆洋表面温度很低。此时岩浆洋自上而下存在一个过渡的瞬态固化"盖层"(淬火层),岩浆洋自上而下存在温度梯度,岩浆洋在该梯度下发生热扩散效应(Soret效应),Soret效应导致上部结晶斜长石的熔体富Ca和贫Na,因此结晶的斜长石An牌号高。     

深吃水半潜式平台参数共振研究

深吃水半潜式平台(deep draft semi-submersible,DDS)作为一种新型海洋结构物,既继承了传统半潜式平台的优点,又改善了传统半潜式平台垂荡运动性能差的不足。但随着吃水的增加,DDS纵摇运动参数共振也成为一个不容忽视的问题。当DDS纵摇运动固有周期和垂荡运动周期满足一定关系时,纵摇运动将发生参数共振,纵摇角度将会显著增大。研究推导了DDS纵摇运动方程,并简化为标准的马修方程,运用希尔无穷行列式法求解马修方程,得到了含阻尼的马修稳定性图谱,并结合具体算例讨论了不同参数对DDS纵摇运动参数共振问题的影响。研究表明:深吃水半潜式平台的参数共振,是设计人员在设计之初必须考虑的问题;通过合理选取平台的系统参数,可以有效避免纵摇运动参数共振现象的发生。     

一种利用单张影像进行规则物体三维重建的方法

提出了一种以单张影像为基础,基于灭点几何原理、共线条件方程及共面约束条件,进行规则物体三维重建的方法。该方法通过影像中的3条两两垂直的直线,利用灭点几何原理得到了影像的方位角元素;利用解算的角元素及共线方程得到了摄影中心坐标;最后,利用解算的影像外方位元素及共面约束条件得到规则物体的三维几何模型。     

Diagnosis of the forcing of inertial-gravity waves in a severe convection system

The non-hydrostatic wave equation set in Cartesian coordinates is rearranged to gain insight into wave generation in a mesoscale severe convection system. The wave equation is characterized by a wave operator on the lhs, and forcing involving three terms—linear and nonlinear terms, and diabatic heating—on the rhs. The equation was applied to a case of severe convection that occurred in East China. The calculation with simulation data showed that the diabatic forcing and linear and nonlinear forcing presented large magnitude at different altitudes in the severe convection region. Further analysis revealed the diabatic forcing due to condensational latent heating had an important influence on the generation of gravity waves in the middle and lower levels. The linear forcing resulting from the Laplacian of potential-temperature linear forcing was dominant in the middle and upper levels. The nonlinear forcing was determined by the Laplacian of potential-temperature nonlinear forcing. Therefore, the forcing of gravity waves was closely associated with the thermodynamic processes in the severe convection case. The reason may be that, besides the vertical component of pressure gradient force, the vertical oscillation of atmospheric particles was dominated by the buoyancy for inertial gravity waves. The latent heating and potential-temperature linear and nonlinear forcing played an important role in the buoyancy tendency. Consequently, these thermodynamic elements influenced the evolution of inertial-gravity waves.     

新疆外向型经济发展效率评价及影响因素

大力发展外向型经济是丝绸之路经济带建设的重要内容。为了研究新疆外向型经济的发展及其影响因素,采用熵值-TOPSIS评价模型和结构方程模型,建立了包括外向型经济发展水平、经济基础水平、社会基础水平和竞争力水平4个指标因素的综合指标体系,对新疆各地州市外向型经济发展效率进行评价,并对4个指标因素的关系进行实证分析。研究结果表明:新疆各地州市外向型经济发展效率差异虽然较小,但呈现小幅度加大趋势;将新疆15个地州市分为超效率发挥地区、领先地区、效率未发挥地区和落后地区;经济基础水平对外向型经济发展水平的影响最大,竞争力水平次之,社会基础水平对外向型经济发展水平暂无明显影响。     

六边形格网的快速傅里叶变换

全球离散格网系统是支持多源地球空间数据融合处理的新型数据模型,傅里叶变换是联系其空域与频域的纽带,对以格网系统为框架的遥感图像的增强具有重要意义。根据三孔六边形格网剖分方案,设计了一种规则六边形格网单元组合结构,并将该结构空间域的二维离散傅里叶变换转化为可以用蝶形算法加速的标准一维变换。采用遥感影像进行实验验证,结果表明本文提出的快速傅里叶变换算法正确、高效,其复杂度为N log2N。随着数据量增大,效率以指数函数形式提高。