河流冲刷过程中表层床沙粗化对不平衡输沙的影响

在分析前人的不平衡输沙研究成果的基础上,针对非均匀沙河床,提出了床沙交换速率的新物理概念,计算研究了不同床沙交换速率时表层床沙的粗化过程及非均匀沙含沙量恢复饱和过程.研究表明,由于较细泥沙的冲刷率总大于较粗泥沙,因此在床面薄层内泥沙随冲刷迅速粗化,致使挟沙力降低,不平衡输沙距离较均匀沙情况大大延长.床沙交换速率愈慢,则冲刷距离愈长.     

粉尘释放和沉积机制的研究进展

风蚀地表释放的粉尘气溶胶在其输送和沉积过程中产生的直接和间接环境效应促进了对其释放和沉积机制的研究.随着土壤风蚀研究的发展,对粉尘释放机制有了较为深入地研究,从简单的经验方程模型发展到目前考虑粉尘释放微观过程的具有清晰物理机制的释放模型,并在大尺度沙尘预报研究中得到了广泛应用.粉尘沉积主要集中于对干沉积和云下清除过程的研究,而对云内清除过程认识不足.简要回顾了粉尘释放和沉积机制研究的发展历史,系统地评述了研究的现状,提出了粉尘释放和沉积模拟研究中存在的问题和今后的发展趋势.     

有关粉尘释放模型的应力分配模式存在问题的讨论

准确模拟粉尘释放通量对评价粉尘气溶胶的气候效应、沙漠化和沙尘暴防治具有重要意义。敏感性试验、室内和野外风洞实验表明被广泛使用的DPM（Dust Production Model）粉尘释放模型的2个应力分配模式——Marticorena模式和 Alfaro模式存在明显问题：由于目前空气动力学粗糙度模式还不能考虑粗糙元间隙率和粗糙元分布状况空气动力学粗糙度的影响,以空气动力学粗糙度为主要参数的Marticorena模式和 Alfaro模式还不能考虑粗糙元间隙率和粗糙元分布状况对应力分配的影响,而相关实验表明这些因素对应力分配存在显著影响;Marticorena模式和 Alfaro模式预测的应力分配系数和起动摩阻风速存在显著差异,目前实验结果还不能判断二者正确与否;Marticorena模式和 Alfaro模式预测的能够有效控制风蚀的应空气动力学粗糙度与实际观测相矛盾。针对上述问题提出了通过风洞实验改进当前应力分配模式的主要途径。     

国内外风蚀监测方法回顾与评述

为了准确认识风沙运动规律、建立风蚀模型,必须对风沙过程进行野外实地监测.鉴于风沙过程的复杂性,目前风蚀监测的方法多种多样.根据监测目的和原理的差异,将现有的主要风蚀监测方法分为风蚀量监测和输沙率监测两大类分别评述.风蚀量监测主要包括集沙盘法,降尘缸法,风蚀盘法,风蚀圈法,示踪法,遥感法,侵蚀针法等;输沙率的监测主要使用...     

Progress on Process and Mechanism of Sand and Dust Emission on Gobi

Gobi is one of the most important landscapes in northwest China, and it is also one of the dust sources in north China and even in central Asia. Based on the different land surface characteristics on the gobi surface, sand and dust emission process and mechanism are obviously different with other landscapes, such as sandy desert. Dust emission process and mechanism on the gobi surface were analyzed in this paper. Wind power system, geomorphology pattern and underlying characteristics were considered for their effect on the sand and dust emission process. Then, the mechanism of land surface characteristics on threshold wind velocity was analyzed. Finally, based on the previous studies on dust emission and mechanism, and in combination with the regional and global requirement, we suggested that the land surface characteristics parameterization, identification of the dust sources and sediment emission mechanism should be the main issues in the future gobi sand and dust research.     

湖泊数值模拟研究现状综述

作为陆面过程的重要组成部分,湖泊在天气气候预测中的作用得到了相关研究者的广泛关注,并成为大气科学研究领域中的一个热点.主要综述了当前湖泊模式的基本类型、所考虑的关键物理过程及其参数化方案,并尝试分析了各个方案的优劣以及模拟效果.相关研究表明,现有的湖泊模式对浅湖的模拟比较成熟,而对深湖和冰湖的模拟有待改进.未来的研究亟需构筑适用于大湖、深湖以及冰湖的参数化方案,发展能全面模拟各类型湖泊的数值模式,并且湖泊数值模拟的改进依赖于今后更多高质量的全球湖泊观测结果.     

Wind Tunnel Experiment of Anti-erosion Efficiency on the Sand Beds Coverd by Different Shapes of Roughness-Elementes

In order to study the relationship between the shapes of roughness-elements on sand beds and the surface sand activity inhibition, we chose six shapes of elements including spherical, triangular pyramid shape, cylindrical, square shape, pie and hemispherical shape by hand with equal quality kept. We carried out the experiment with the 10% coverage on the wind tunnel. The results revealed that ① the erosion and anti-erosion rate of spherical, triangular pyramid shape, cylindrical and square roughness-elements were better than the pie and hemispherical on the non-sand wind; ② On the sand-driving wind conditions, spherical, triangular, cylindrical covered beds became erosion to erosion-deposition with the increase of wind speed, and the erosion rate was increased with the wind speed. When the wind speed was more than 10 m/s, the sand-beds showed a strong erosion, and the pie and hemispherical elements’ resistance function were weakest; ③ No matter the non-sand wind or sand wind, the erosion rate was affected by the elements’ aspect ratio, height and spacing. The slender elements with a prominent upper edge were clearly superior to broad rounded elements.     

气候变化对中国农业温度阈值影响研究及其不确定性分析

气候变化影响的温度阈值已经成为国际谈判的焦点问题。利用区域气候模式和作物模型相连接的方法,在50 km×50 km的网格尺度上模拟了IPCC (International Panel of Climate Change) SRES (Special Report on Emissions Scenarios) A2和B2情景下2011—2040年、2041—2070年和2071—2100年我国3种主要粮食作物（水稻、小麦和玉米）的平均单产变化情景,结合同时段的中国地区温度升高状况分析了造成我国主要粮食作物产量持续下降的升温阈值,并对阈值研究中的不确定性进行了初步分析。结果表明：如果同时考虑升温和CO2的肥效作用对作物的影响,目前预测的气温升高范围（0.9～3.9℃）中将不存在威胁我国粮食生产的温度阈值;而如果仅考虑升温对作物的影响时,全国平均温度升高2℃以后,将导致我国粮食单产水平的持续下降,威胁未来的粮食生产;气候变化适应措施如充分灌溉、播种期的调整和品种更替对阈值的确定有一定的影响,如单考虑充分灌溉可以使上述升温阈值延后到2.5℃左右,而播种期的调整和品种的更替也会对产量和产量变率造成一定的影响,进而调整温度阈值;目前研究的不确定性主要来源于情景、方法和适应措施3个方面。     

1955-2011年兰州沙尘暴、浮尘天气事件发生概率的Markov模型研究

依据甘肃兰州市1955-2010年沙尘暴、 浮尘天气事件年变化资料, 划分年强度分级, 应用Markov模型对其不同强度发生概率进行分析, 在此基础上预测和检验了2011年兰州沙尘暴浮尘天气事件的发生概率.结果显示: 2011年沙尘暴发生的特强年、 强烈年、 强发生年、 一般发生年和少发年的概率为,而事实上2011年发生沙尘暴0次,属于少发年, 符合预测结果; 2011年浮尘天气发生的特强年、 强烈年、 强发生年、 一般发生年和少发年的概率为,而事实上2011年发生浮尘9次,介于平常年和少发年范围, 符合预测结果.随着时间序列的延长, Markov模型可成为短期沙尘暴浮尘天气变化预测的有效途径.     

Review of Methodologies for Offshore Wind Resource Observation and Assessment

Observation and assessment of wind resources is a prerequisite for wind farm construction. Due to the investment cost of offshore wind farm is very expensive, more accurate assessment of wind resources is needed to reduce their investment risks. From traditional field observation to multi-platform remote sensing and from ordinary mathematical statistics to coupled numerical model simulation, abundant offshore wind data and evolving assessment methods make the results of offshore wind resource assessment more and more reliable. Poor station observations and rich remote sensing data are distinct characteristics of offshore wind data. Technology integration of applying multi-scale coupled models to assimilate multi-source remote sensing and station data is a mainstream development direction of offshore wind resource assessment methods. The wind resource assessment for offshore wind farm should focus on data quality and method selections of data interpolation, wind speed calculation of return period and wind energy parameters adjusted for a long term condition because these factors can significantly affect the operating efficiency of future wind farm.     

利用声发射研究郯庐断裂北段古应力事件

采用声发射实验方法,测试分析了郯庐断裂带北段古构造应力场,结果显示郯庐断裂北段西侧自晚奥陶世以来,经历了8次古构造事件,最大主应力有效值为153.6MPa;从早二叠世至早燕山期,测区构造运动很弱;早白垩世以来有4次古构造事件。由此推断依兰-伊通断裂和哈尔滨-长春断裂形成于古生代,燕山运动使其演化成大型走滑断裂。