中国陕西关中及周边地区近500年来初夏干燥指数序列的重建

本文采用华山东峰、西峰和南峰的华山松树轮宽度差值年表重建了1500年以来中国陕西关中及周边地区的初夏干燥指数序列,对重建序列进行了统计特征分析,并同大尺度大气环流场进行了相关分析。结果表明:华山年表的变化与该地区初夏平均干燥指数序列的变化具有很好的一致性,可用来重建该地区的初夏干燥指数序列;该地区在1502～1511年、1570～1580年以及1807～1814年间的初夏季节存在3次较为严重的干旱;该地区初夏干燥指数变化存在着较为明显的周期特征,其中以13a左右和4a左右的周期最为显著,但周期特征在不同的历史阶段存在着明显的差异;重建序列在1784年前后发生了一次较大幅度的方差变化,而1587年前后的均值突变则表现为干燥指数值的急剧降低;该地区初夏季节的干燥程度可能与前期极涡的中心强度及冷空气活动有关。     

花岗岩风化程度的化学指标及微观特征对比——以香港九龙地区为例

据香港九龙3个不同工程场地取得的149件不同级别的风化花岗岩样品的化学分析结果,用统计学方法,从反映岩石风化程度的18项化学指标中选取9项进行了分析计算.对其结果及其与风化程度分级的关系的研究表明有4种指标比较理想.通过对样品微观特征的观察研究和矿物成分、微孔隙率以及综合显微岩石指标(I_p)进行了描述和定量分析,发现其中一些指标有一定相关性.这些化学指标和微观特征相关的统计值在一定程度上可定量表征花岗岩的风化程度,即:随风化作用进行,碱、碱土金属组分逐渐淋失,脱硅、富铝铁化作用逐渐加强;相应地,先是钠长石风化成高岭石,其次为云母和钾长石的风化.粘土矿物所占体积百分比随风化程度增高而变大,至残积土(Ⅵ级)时已达50%左右;I_p指标值下降,微孔隙率增高.文章综合出各个风化级别的指标变化范围及平均值供花岗岩分布区花岗岩风化野外调查和研究工作参考.     

Drought monitoring

Drought detection, monitoring and indices are closely related to its definition. The specific definition chosen for a particular drought analysis will affect the procedures one uses in drought detection and monitoring. The traditional Palmer Drought Severity Index (PDSI) has been proven to be ineffective in regions of predominantly irrigated agriculture.The recently developed ALERT (Automated Local Evaluation in Real Time) system is proposed for use in monitoring the spatial and temporal variations of drought in real time. The ALERT system uses standardized instruments, radio frequencies, software and hardware. It was originally developed as a flash flood waming system by local flood control districts and the National Weather Service. However, now it has expanded to over 100 other uses in the areas of natural and man-made disaster detection and warning. The successful ALERT system indicates the need for the continued development of a national drought monitoring index that is applicable to a wide range of climate, hydrologic and water resource environments.     

Index and Composites of the Kuroshio Meander South of Japan

Using the merged NOAA National Oceanographic Data Center (NODC)/Japan Oceanographic Data Center (JODC)/Marine Information Research Center (MIRC) historical hydrographic dataset, a new Kuroshio large meander (LM) index is introduced. This index helps to distinguish between the LM events and other types of Kuroshio Current (KC) variability south of Japan. Observations, re-systematized according to the index, provide composite patterns of typical formation and decay of the LM. The patterns reveal a remarkable similarity between individual LMs and support the deterministic rather than the stochastic model of LM evolution on a time-scale of one year. A “trigger” meander (TM) occurs on composite maps six months prior to the LM formation as a 1° latitude southward shift of the KC axis south of Kyushu. When propagating eastward along the coast of Japan, TM gradually increases in area. In principal the emergence of LM takes only one month. East of TM and LM a remarkable onshore shift of the KC is noticed, supplying the coastal region with warm water. Other warm anomalies are found on the warm side of KC next to the propagating TM and in the larger warm eddy area southeast of Kyushu. Different LMs survive for different times and decay in some months after KC “jumps” across the Izu Ridge. Changes of water properties on isopycnals in the interior of LM can be roughly described by two-layer kinematics with an interface at σ_θ = 27 which suggests a strong inflow of deep Kuroshio waters into the LM core during the formation of the latter. This revised version was published online in August 2006 with corrections to the Cover Date.     

漠河樟子松树轮指数与标准化植被指数的关系研究

利用我国寒温带针叶林的樟子松树轮数据和多年NDVI数据,运用树轮指数生成程序ARSTAN得到最大密度、晚材密度等7种树轮指数的标准化序列。首先分析了森林NDVI的逐月和逐年变化特征,然后分析了各种树轮指数与森林NDVI的关系。结果表明,漠河森林NDVI月变化和年变化主要受温度影响,属于温度驱动型;最大密度指数与NDVI年均值间有较强的相关关系;生长季（5～9月）NDVI与当年树轮的最大密度、晚材密度、早材密度和晚材宽度指数相关,但与最小密度、树轮宽度、早材宽度指数关系不显著;夏季（6～8月）NDVI与早材密度指数显著相关,但早材宽度指数却与前一年夏季NDVI有关。就单月NDVI而言,5月份的NDVI与最大密度和晚材密度指数显著相关,而6月份的NDVI与早材密度指数显著相关。从7种树轮指数对区域尺度上的生长季NDVI的指示效果来看,密度指数比宽度指数更有效。     

海南岛不同地形上土壤性质的多样性分析

多样性指数长时间以来在生态学领域被用于分析不同生态体的发生规律,本研究将类似手段用于某些土壤性质 (土壤发生层次、土层厚度和土壤容重) 多样性的分析中,讨论基于海南岛土壤－地形体数字化数据库 (SOTER),通过对不同地形上土壤发生层次、土层厚度和土壤容重等某些土壤性质类别SOTER单元的丰富度指数 (S)、多样性指数 (Shannon指数H') 和均匀度指数 (Pielou E) 的计算,类别多度分布模型的应用,并在地理信息系统环境中实现了海南岛不同地形上某些土壤性质多样性分析的数字化表达。     

缺氧环境及地球化学判识标志的探讨--以鄂尔多斯盆地为例

在地质历史时期,古缺氧环境对沉积有机质的数量和质量都具有重要意义.对于优质烃源岩而言较高的有机质数量、较好的有机质质量无疑是主要条件.在综合国内外研究成果的基础上,结合鄂尔多斯盆地奥陶系碳酸盐岩的微量元素和有机质丰度等的研究,着重讨论了微量元素、稳定同位素和有机质等判识缺氧环境的地球化学指标情况,并建立了缺氧环境基本特征及判识指标的综合体系.缺氧沉积中一般为V、Mo、Zn等金属和有机碳富集程度高,DOP＞0.40,V/(V Ni)＞0.45,U/Th＞0.75,δCe＞-0.1,Pr/Ph＜1.研究表明,地球化学-沉积学的综合指标能更有效地判识和反演古缺氧环境.