全球气候变暖中南北半球海冰变化的差异

应用海冰面积资料,分析在全球气候变暖下,南北半球海冰季节和年际变化的差异,结果表明:冬季南半球海冰面积为北半球的1.13倍,而夏季仅为北半球的2/5,南半球海冰的季节变化比北半球更为显著,其季节振幅为北半球的1.6倍.1979--2006年,北半球海冰总面积呈显著减少趋势,夏秋季最快,特别在1990年代中后期以来,减少尤为迅速;夏秋季,整个区域海冰为均一的减少趋势,北冰洋靠近北太平洋的近海变化最为迅速,冬春季,主要发生在北太平洋海域.南半球海冰自1980年代初以来有所增多,四季整个区域海冰并未呈均一的减少趋势,而是有一显著减少中心,位于南极半岛附近,两个增多中心,分别位于罗斯海外围和西南印度洋一带.随夏一秋一冬一春的季节转换,3个中心区域位置存在东移和返回的过程.     

Boundary-Layer Stress Instabilities in Neutral,Rotating Turbulent Flows

Boundary-layer instabilities are studied by analyzing the results of laboratory simulations of wall turbulence in a shear-driven rotating flow. The experiments were carried out in the Turin University Laboratory rotating water tank, where a circular flow was generated by either increasing (spin-up) or decreasing (spin-down) the rotation speed of the platform. The flow was measured using a Particle Image Velocimetry technique and the developed turbulence analyzed. Two cases were accounted for, in the former the measurements were performed over a smooth surface (bottom of the tank), while in the latter a rough-to-smooth transition was considered. The turbulent boundary layer developed inside the tank is analyzed by means of vertical profiles of mean and turbulent quantities and on the basis of drag coefficients. Then turbulent structures developed in the different cases are shown and discussed in terms of the vorticity fields. Finally, an analysis based on the concept of swirling strength was carried out to select among the vortex extremes those associated with a coherent structure.     

Radiative Processes in the Stable Boundary Layer: Part II. The Development of the Nocturnal Boundary Layer

The interaction between radiation and turbulence in the stable boundary layer over land is explored using an idealized model, with a focus on the surface layer after the evening transition. It is shown that finer vertical resolution is required in transitional boundary layers than in developed ones. In very light winds radiative cooling determines the temperature profile, even if similarity functions without a critical Richardson number are used; standard surface similarity theory applied over thick layers then yields poor forecasts of near-surface air temperatures. These points are illustrated with field data. Simulations of the developing nocturnal boundary layer are used to explore the wider role of radiation. Comparatively, radiation is less significant within the developed stable boundary layer than during the transition; although, as previous studies have found, it remains important towards the top of the stable layer and in the residual layer. Near the ground, reducing the surface emissivity below one is found to yield modest relative radiative warming rather than intense cooling, which reduces the potential importance of radiation in the developed surface layer. The profile of the radiative heating rate may be strongly dependent on other processes, leading to quite varied behaviour.     

中国耕地和农村宅基地利用转型耦合特征与机制(英文)

Land use transition refers to the changes in land use morphology (both dominant morphology and recessive morphology) of a certain region over a certain period of time driven by socio-economic change and innovation, and it usually corresponds to the transition of socio-economic development phase. In China, farmland and rural housing land are the two major sources of land use transition. This paper analyzes the spatio-temporal coupling characteristics of farmland and rural housing land transition in China, using high-resolution Landsat TM (Thematic Mapper) data in 2000 and 2008, and the data from the Ministry of Land and Resources of China. The outcomes indicated that: (1) during 2000-2008, the cor-relation coefficient of farmland vs. rural housing land change is -0.921, and it shows that the change pattern of farmland and rural housing land is uncoordinated; (2) the result of Spear-man rank correlation analysis shows that rural housing land change has played a major role in the mutual transformation of farmland and rural housing land; and (3) it shows a high-degree spatial coupling between farmland and rural housing land change in southeast China during 2000-2008. In general, farmland and rural housing land transition in China is driven by socio-economic, bio-physical and managerial three-dimensional driving factors through the interactions among rural population, farmland and rural housing land. However, the spatio-temporal coupling phenomenon and mechanism of farmland and rural housing land transition in China are largely due to the "dual-track" structure of rural-urban develop-ment.     

地基微波辐射计对咸宁一次冰雹天气过程的监测分析

利用咸宁MP-3000A地基微波辐射计探测资料对2010年4月12日发生在咸宁的一次冰雹天气过程进行了监测分析。结果表明:(1)在这次冰雹天气过程中,冰雹云中上升气流非常强盛,引起云底高度剧烈波动,同时将底层空气的感热和潜热向上输送导致等温线上抬,并伴随贝吉隆增长和过冷水滴与冰晶消耗等过程,由于这些宏观和微观过程使得整层水汽与液态水含量连续出现下降和上升过程,产生了多峰结构;(2)在4.2—8km高度过冷层的冰雹云中,08时40分—13时的固、液、气混合相态变化非常复杂,过冷水滴与冰粒子消耗过程、贝吉隆过程和过冷水滴与冰晶增长过程交替出现,产生了相对湿度在6km以下低于80%的区域,且液态水含量在4.2—8km高度处出现0.7—1.8g/m3的大值区,从而形成了冰雹生长过程中交替干、湿增长生长环境,非常有利于冰雹粒子群快速累积以及分层增长;(3)利用微波辐射计资料计算分析了MKI、KI、TT和HI四个不稳定指数,这些指数对强对流天气有很好的指示作用,并对强对流天气有一定的临近预警潜力,若选取KI≥38作为该地区强对流天气预警指标,可以提前45min预警第1次降雹强对流天气,且分别提前20、40和42min预警第2、3、4个对流单体影响该地区。     

A Typical Mode of Seasonal Circulation Transition: A Climatic View of the Abrupt Transition from Drought to Flood over the Middle and Lower Reaches of the Yangtze River Valley in the Late Spring and Early Summer of 2011

In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.     

一次变性台风再增强过程的敏感性试验

采用位涡反演技术与数值模拟相结合的方法,通过初值敏感性试验和物理量场的诊断分析,对台风变性后再度增强的影响因子和物理机制进行了深入的分析和研究。结果表明:台风低压由变性减弱转为发展增强主要是由于台风低压环流与西风带斜压锋区之间的相互作用所造成的,随着高空冷涡低槽的加深南下和台风低压的继续北上,两个系统之间的距离逐渐减小,西风带高空槽与台风低压之间相互作用的正反馈机制逐步成为台风变性后强烈加深发展的主要原因。     

加强科技成果管理 服务铀矿地质工作

通过总结铀矿地质科技成果管理的实践经验,结合科研与生产实际,提出科技成果管理中存在的问题和对策建议。     

AutoCAD DXF图形的批量无损投影转换方法

详细研究AutoCADDXF图形数据文件结构,实现AutoCAD图形批量无损投影换带转换的有效技术方法,采用VB程序设计编程,开发配套应用程序,具有工程效益和推广价值。     

Fluid Evolution and Metallogenic Dynamics during Tectonic Regime Transition: Example from the Jiapigou Gold Belt in Northeast China

The Jiapigou gold belt, one of the most important gold-producing districts in China, is located in the northern margin of the North China Craton (NCC). The tectonic evolution of the gold belt is closely related to the Siberian Plate (SP) in the north, Yangtze Craton (YC) in the south and Pacific Plate in the east. In order to investigate the nature of the tectono-fluid-metallogenic system, the authors investigated the relationships among the tectonic regimes, fluid evolution and metallogenesis. This paper examined the corresponding spatial–temporal relationship between the ore-controlling tectonic regime and hydrothermal fluid evolution in the Jiapigou gold belt. There are two types of gold mineralization: disseminated ores that are distributed within the NW-trending main ductile shear zone and gold-bearing quartz veins and minor disseminated ores that are distant to the ductile shear zone. The fluid inclusions in quartz contain a large amount of CO₂. Metamorphic fluids of middle to high temperatures and pressures and meteoric waters of low temperatures and pressures mixed together during mineralization. A proposed ore-forming model is as follows: in the pre-ore phase, the collision of SP and NCC resulted in the NS-trending compression of the ore belt. This formed the NE-trending and NW-trending shear faults and EW-trending folds. During the ore-forming phase, the collision of YC and NCC resulted in dextral shearing of the NW-trending Jiapigou fault and the NE-trending Green faults. High-pressure fluids caused by the compression flowed into the dilatant zone. This may have caused both phase separation of CO₂-bearing fluids and the mixing of meteoric waters, metamorphic waters and magmatic source fluids and finally resulted in the disequilibrium of the ore fluids and precipitation of ore minerals.