淮南市区浅层地下水求参公式的建立

根据淮南市区浅层地下水埋深浅，滞后效应小等特点，推导出一套实用的水文参数计算公式，包括：降水入渗补给地下水系数ａ，蒸发极限深度Ｌ，蒸发系数Ｃ，以及浅层地下水的给水度ｕ的计算公式。     

Coastal Massachusetts pond development: edaphic,climatic, and sea level impacts since deglaciation

Kettle ponds in the Cape Cod National Seashore in southeastern Massachusetts differ in their evolution due to depth of the original ice block, the clay content of outwash in their drainage basins, and their siting in relation to geomorphic changes caused by sea-level rise, barrier beach formation, and saltmarsh development. Stratigraphic records of microfossil, carbon isotope, and sediment changes also document late-glacial and Holocene climatic changes.The ponds are separated into 3 groups, each of which follow different development scenarios. Group I ponds date from the late-glacial. They formed in clay-rich outwash, have perched aquifers and continuous lake sediment deposition. The earliest pollen and macrofossil assemblages in Group I pond sediments suggest tundra and spruce-willow parklands before 12 000 yr B.P., boreal forest between 12 000 and 10 500 yr B.P., bog/heath initiation and expansion during the Younger Dryas between 11 000 and 10 000 yr B.P., northern conifer forest between 10 500 and 9500 yr B.P., and establishment of the Cape oak and pitch pine barrens vegetation after 9500 yr B.P. Sedimentation rate changes suggest lowered freshwater levels between 9000 and 5000 yr B.P. caused by decreased precipitation on the Atlantic Coastal Plain. Lake sediment deposition began in the middle Holocene in Group II ponds which formed in clay-poor outwash. These ponds date from about 6000-5000 yr B.P. In these ponds sediment deposition began as sea level rose and the freshwater lens intersected the dry basins. The basal radiocarbon dates of these ponds and stable carbon isotope analyses of the pond sediments suggest a sea-level curve for Cape Cod Bay. Holocene topographic changes in upland and the landscape surrounding the ponds is reconstructed for this coastal area.Group III ponds in the late Holocene landscape of the Provincelands dunes originated as interdunal bogs about 1000 yr B.P. and became ponds more recently as water-levels increased. Peat formation in the Provincelands reflects climatic changes evident on both sides of the Atlantic region.This is the 8th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

砖窑沟流域农地生产潜力的层次分析──以糜子作物为例

以糜子作物为例,分析了河曲县砖窑沟流域农地生产潜力的层次,以及影响生产潜力的主次因素等,计算了流域理想的生产潜力与实际生产潜力。通过分析计算,提出了提高农地增产潜力的途径,为提高本流域及晋西北地区农地的增产潜力提供了理论依据与实际应用范例。     

用非色散红外气体分析仪进行大气CO2本底浓度的测量

按WMO关于开展全球CO2监测的要求，在对引进设备进行改进的情况下，建立了我国开展大气CO2本底浓度连续测量的红外气体分析测量系统及有关方法。系统的测量精度优于0.1ppm，完全满足全球本底测量的要求，并具有较好的国际可比性。在此基础上，首次取得了我国大陆上空大气CO2的本底浓度资料。     

Life-cycle cost analysis of design practices for RC framed structures

The objective of this study is to perform life-cycle cost analysis on three design practices namely weak ground storey, short and floating columns and their combinations. Life-cycle cost analysis is recognized as the only suitable tool for assessing the structural performance when the structure is expected to be functional for a long period of time. Life-cycle cost analysis is considered in this study assessing the behaviour of the three design practices against earthquake hazard. Although, a number of checks are performed in order to reduce the influence of these design practices on the seismic behaviour of reinforced concrete (RC) framed structures, it was found that the total life-cycle cost of partially infilled RC designs is significantly increased compared to that of the fully infilled one. Through the test example examined in the framework of this study general conclusions are obtained regarding the behaviour of the three design practices.     

夏季乌拉尔地区环流持续异常及其背景流特征

在 Dole持续异常界定方法的基础上提出了一种适用于全球分析的界定方法 ,并利用NCEP/NCAR 1 980～ 1 998年 6月 1日～ 8月 31日逐日再分析资料 ,分析了全球大气环流持续异常的分布 ,重点研究了乌拉尔地区反复出现的、维持较长时间的强环流异常的背景流及其演变特征 ,得到以下结论 :1 )文中提出的界定方法能较好地识别全球地区持续异常分布 ;2 )乌拉尔地区环流正、负持续异常形成时 ,背景环流的发展不具有对称性 ,负异常并不是正异常的简单相反过程。正异常的发展与位于西南方的正距平扰动向东北移动、及与位于中西伯里亚的正距平扰动西移有关 ,这些扰动具有相当正压结构的 ,而负异常则主要是局地发展而形成的 ;3)正压过程对乌拉尔持续异常的形成起着主要作用 ,明显不同于北太平洋环流持续异常的发展 ;4)乌拉尔正、负持续异常期间的背景流不仅在北半球中高纬有明显差异 ,而且在南、北半球其它地区也有明显差异 ,热带的差异在低频环流上表现得更为清楚 ;5)在异常发生前 ,中纬度急流已发生了有利于异常建立的改变。     

“Greatest lake period” and its palaeo-environment on the Tibetan Plateau

The “greatest lake period” means that the lakes are in the stage of their maximum areas. As the paleo lake shorelines are widely distributed in the lake basins on the Tibetan Plateau, the lake areas during the “greatest lake period” may be inferred by the last highest lake shorelines. They are several, even tens times larger than that at present. According to the analyses of tens of lakes on the Plateau, most dating data fell into the range of 40-25 ka BP, some lasted to 20 ka BP. It was corresponded to the stage 3 of marine isotope and interstitial of last glaciation. The occurrence of maximum areas of lakes marked the very humid period on the Plateau and was also related to the stronger summer monsoon during that period.     

An extreme value analysis of the flow of Burbage Brook

An extreme value analysis of the flow of Burbage Brook is carried out by modelling peaks over a high threshold. The aims are to illustrate recently developed statistical techniques and to report on interesting features of the flow of the brook over a 58-year period. Peak flows are found to show marked seasonal variation and a downward trend. Then-year return level is estimated for various values ofn, and the reliability of the estimates is assessed.     

Differences between Mean Sea Levels for the Pacific,Atlantic and Indian Oceans From Topex/Poseidon Altimetry

Geopotential values W of the mean equipotential surfaces representing the mean ocean topography were computed on the basis of four years (1993 - 1996) TOPEX/POSEIDON altimeter data: W = 62 636 854.10m ² s ^–2 for the Pacific (P), W = 62 636 858.20m ² s ^–2 for the Atlantic (A), W = 62 636 856.28m ²s^–2 for the Indian (I) Oceans. The corresponding mean separations between the ocean levels were obtained as follows: A – P = – 42 cm, I– P = – 22 cm, I – A = 20 cm, the rms errors came out at about 0.3 cm. No sea surface topography model was used in the solution.     

全球资料同化中误差协方差三维结构的准确估计与应用Ⅱ:背景误差协方差调整与数值试验分析

利用NMC方法针对背景误差协方差的方差、三维相关与特征长度来揭示T213L31模式的误差主要特点,并与传统更新矢量方法的计算结果进行了对比与调整。结果表明NMC方法结果与更新矢量方法结果在大体特征上基本吻合,但细节上的差异不可忽视,特别是对背景误差方差与特征长度的估计存在显著的差异,其主要原因是NMC方法倾向于高估天气尺度波的背景误差,而低估次天气尺度到中尺度波的背景误差。通过对背景误差方差、特征长度的调整,显著改善了背景误差功率谱的分布特点,使得NMC方法结果与更新矢量方法结果更为吻合。通过三维变分同化与最优插值中观测与背景误差相对重要性的比较,发现两者结果基本一致,但三维变分同化在850 hPa以下的温度场和300 hPa以上的风场统计结果都表现出背景误差相对于观测误差偏小的特点。背景误差相对于观测误差偏小有助于保证分析场中质量场与风场平衡,消除了大气底层和高层质量场与风场不匹配现象。在数值试验中,针对不同的背景误差均方差与特征长度的特点,分析了分析增量和预报效果的差异,结果表明,准确的背景误差估计与优化工作改善了预报效果,使得北半球三维变分同化的120 h预报效果整体好于现有最优插值。