1.5 Ma以来黄土高原风尘堆积的岩石磁学记录与中更新世气候转型

通过对黄土高原中部朝那剖面黄土-古土壤序列系统的岩石磁学分析,建立了1.5Ma以来黄土高原高分辨率岩石磁学指标演化序列。岩石磁学记录表明本区1.5Ma以来以0.93和0.62Ma为界经历了3个不同的气候演化阶段。在1.5～O.93和0.62～0Ma期间各种磁学参数大致呈同步变化趋势,能较好地与深海氧同位素（MIS）曲线相对应,而在0.93～0.62Ma期间（相当于L9底到L6顶,MIS24-MISl6）,尽管磁化率、饱和剩磁强度（Mr）、饱和磁化强度（Ms）与剩磁矫顽力（Bcr）、矫顽力（Bc）曲线的峰谷能与MIS的峰谷相对比,但该阶段的磁学参数变化幅度和形式明显不同于1.5～0.93和0.62Ma以来的两个演化阶段。磁化率、Mr和Ms在0.93Ma突然降低,此后变幅很小,反映夏季风较弱且相对稳定,一直维持到0.62Ma前后。在0.9Ma前后Bc、Bcr突然增大,可能反映了冬季风突然增强,然后宽幅波动下降。这种变化可能是黄土高原风尘堆积对中更新世气候转型事件的响应。黄土高原岩石磁学记录的中更新世气候转型事件发生于0.93Ma,结束于0.62Ma。造成这次气候转型事件的原因除了与全球冰量和太阳辐射变化有关之外,还可能与中更新世青藏高原急剧隆升而激发的亚洲内陆干旱化加剧,从而导致亚洲内陆沙漠的形成与扩张有关。     

航空摄影立体像对的全自动影像匹配

在原始影像立体像对的基础上,实现ＤＥＭ的全自动提取是“数字摄影测量”的最重要的技术,是“摄影测量”对“数字地球”科学体系的最大贡献。ＤＥＭ全自动提取的关键技术就是立体像对的全自动影像匹配。作者过多年的实践,分别实现了航空影像立体像对的全自动影像匹配和航天影像立体对的全自动影像匹配。从自动内定向,自动相对定向、全数字影像匹配等３个子过程论述了实现航空影像ＤＥＭ全自动提取技术的全过程,并且给出了试验的     

湖南沃溪金锑钨矿床稀土元素特征研究

对湖南活溪金锑钨矿床稀土元素特征的研究结果表明：在成矿过程中,稀土元素发生了从近矿围岩向含矿断裂带或成矿热液的迁移;成矿物质主要来自赋矿地层围岩,且具多源性;矿化程度不同的层脉石英矿石中的稀土总量具有明显的差异。同时指出了将热液金矿床中石英脉内稀土总含量作为找矿标志的可能性。     

湘西保靖白岩洞- 金塘湾洞穴系统的发育特征

白岩洞- 金塘湾洞穴系统,由主洞和10条支洞组成,呈高、中、低洞穴层相互串通的阶梯状结构,洞道长12km(仅探测6390. 4m)。洞穴系统受下寒武统清虚洞组碳酸盐岩地层分布的控制,洞穴发育对中薄层灰岩和中厚层泥晶灰岩具有优选性,其展布方向受NNE、NE向的破裂构造、揉皱破裂带的控制,表现出较强的方向性。本洞穴系统形成于白垩- 第三纪,至今仍在向纵深发育。洞穴系统演化的空间结构,由早期高层洞、中期中层洞、晚期低层洞依序演变,并由南西向北东逐级演化,在其演化过程中,为垂向、斜向、阶梯式洞道所串通,构成层楼式的网络状洞穴系统。      

地学三维模型光照与动态显示

介绍了一种具有真实感的地学三维模型光照显示的新方法,给出了三角网构建和曲面样条函数插值方法,讨论了适应三维模型光照显示的可见性测试、光照模型等算法和方法,实现了模型动态显示和剖面绘制。      

基于模型的3D3C采集设计与评价

对目前三维三分量(3D3C)地震勘探数据采集设计的方法进行了系统分析,利用聚焦射束分析技术(CFP),提出了基于模型的3D3C采集设计方法及其评价的参数。从模型出发的设计方法,能够使3D3C的采集结果更加真实可靠。      

气候与环境预测和调控中的数学问题

数学无所不在,现代科学与数学的发展是相互促进的,未能用严谨的数学方式表达的科学问题难于说是属于现代科学范畴的,现代的数学方法与现代提出的科学问题密切地结合是解决问题的关键.作者论述了现代的气候与环境预测和调控中的一些重要的数学问题,其中第一个问题即预测问题,也包括数值天气预测等在内.在这方面论述的问题有预测问题提法的适定性;非线性系统的分叉、混沌、突变等和可预测时效的关系;不完整的观测资料四维同化问题;不同分辨率模式的嵌套问题;和数值求解的算法问题.第二个问题是自然环境的调控或即自然控制论,举例分析了人工影响天气、改良局部气候、泥沙冲淤调控和最优航道工程、以及生态建设规划等问题.       

基于遥感和GIS的中国20世纪90年代毁林开荒状况分析

毁林开荒过程是一种林地变为耕地的土地利用变化过程,可以通过遥感和GIS技术对这一过程进行监测。本文通过覆盖全国的TM影像数据,对20世纪90年代林地转为耕地的面积及其空间分布进行分析,从而对全国毁林开荒过程进行遥感监测。结果表明,该时期有17630km²的林地被开垦为耕地。不同面积等级的开垦过程在不同流域分布也不同:面积小于10hm²和介于10～100hm²的被开垦林地较广泛地分布于各大流域;而面积介于100～1000hm²的被开垦林地主要分布于松辽流域、黑龙江流域和东北东部流域、长江流域、珠江流域和云南省所在流域;大于1000hm²的被开垦林地则几乎全部分布于松辽流域、黑龙江流域和东北东部流域。坡度大于3°的毁林开荒地面积占总面积的295%;对土壤侵蚀背景的分析表明,土壤侵蚀强度以微度和轻度为主     

A Numerical Study on Effects of Land-Surface Heterogeneity from ‘Combined Approach’ on Atmospheric Process Part II: Coupling-Model Simulations

Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version le (B0Z) and the other B1Z based on B0Z and heterogeneously-treated by ‘combined approach’ , were coupled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weath-er modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that B1Z, compared with B0Z, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with B1Z, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the significantly-heterogeneous Land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.     

A Numerical Study on Effects of Land-Surface Heterogeneity from “Combined Approach” on Atmospheric Process Part I: Principle and Method

A method based on Giorgi (1997a, 1997b) and referred to as ‘combined approach’, which is a combination of mosaic approach and analytical-statistical-dynamical approach, is proposed. Compared with those of other approaches, the main advantage of the combined approach is that it not only can represent both interpatch and intrapatch variability, but also cost less computational time when the land surface heterogeneity is considered. Because the independent variable of probability density function (PDF) is extended to the single valued function of basic meteorological characteristic quantities, which is much more universal, the analytical expressions of the characteristic quantities, (e.g., drag coefficient, snow coverage, leaf surface aerodynamical resistance) affected by roughness length are derived, when the roughness length (and/ or the zero plane displacement) heterogeneity has been mainly taken into account with the approach. On the basis of the rule which the PDF parameters should follow, we choose a function y of the roughness length z0 as the PDF independent variable, and set different values of the two parameters width ratio αn and height ratio γ of PDF (here a linear, symmetric PDF is applied) for sensitivity experiments, from which some conclusions can be drawn, e.g., relevant characteristic terms show different sensitivities to the heterogeneous characteristic (i.e., roughness length), which suggests that we should consider the heterogeneities of the more sensitive terms in our model instead of the heterogeneities of the rest, and which also implies that when the land surface scheme is coupled into the global or regional atmospheric model, sensitivity tests against the distribution of the heterogeneous characteristic are very necessary; when the parameterαn is close to zero, little heterogeneity is represented, andαn differs with cases, which have an upper limit of about 0.6; in the reasonable range ofαn, a peak-like distribution of roughness length can be depicted by a small value ofγ, etc..