土地利用和气候变化对海河流域蒸散发时空变化的影响

蒸散发（ET）是水文能量循环和气候系统的关键环节,研究ET的时空变化特征及其响应土地利用和气候变化的驱动机制对于理清流域水资源和气候变化的关系具有重要的意义。本文基于MOD16/ET数据集定量分析了海河流域2000-2014年ET的时空变化特征,并结合时序气温降水数据和土地利用数据,采用相关分析方法定量探索了ET与气候因子的驱动力关系。结果表明：① 海河流域2000-2014年ET表现为较为显著的空间分布格局,呈现出北部和南部高、西北部和中东部低的分布特性。不同土地利用类型的多年ET呈林地>草地>耕地>其他类型的特征;② 2000-2014年海河流域年均ET波动范围为371.96~441.29 mm/a,多年ET的均值为398.69 mm/a,平均相对变化率为-0.41%,整体呈下降趋势;③ 多年月ET与气温和降水均呈单峰型周期性变化趋势,年内月ET呈单峰变化趋势;④ 春秋两季的ET与降水和气温的相关性明显高于其他季节,ET与气温和降水的平均相关系数是-0.17和0.37,表明降水对于ET的响应程度强于气温;⑤ 驱动分区结果表明海河流域ET受气候因子驱动的主要类型是降水驱动型和降水、气温共同驱动型;⑥ 海河流域耕地ET变化气候因子驱动模式主要是降水、气温共同驱动型;林地、草地的驱动模式主要气温驱动型和降水驱动型,其他土地利用类型的驱动模式主要是受其他因素驱动。该研究将对海河流域水资源开发管理和区域气候调节起到科学指导作用。     

Spatio-temporal Variation of Soil Respiration and Its Driving Factors in Semi-arid Regions of North China

Soil respiration (SR) is the second-largest flux in ecosystem carbon cycling. Due to the large spatio-temporal variability of environmental factors, SR varied among different vegetation types, thereby impeding accurate estimation of CO₂ emissions via SR. However, studies on spatio-temporal variation of SR are still scarce for semi-arid regions of North China. In this study, we conducted 12-month SR measurements in six land-use types, including two secondary forests (Populus tomentosa (PT) and Robinia pseudoacacia (RP)), three artificial plantations (Armeniaca sibirica (AS), Punica granatum (PG) and Ziziphus jujuba (ZJ)) and one natural grassland (GR), to quantify spatio-temporal variation of SR and distinguish its controlling factors. Results indicated that SR exhibited distinct seasonal patterns for the six sites. Soil respiration peaked in August 2012 and bottomed in April 2013. The temporal coefficient of variation (CV) of SR for the six sites ranged from 76.98% to 94.08%, while the spatial CV of SR ranged from 20.28% to 72.97% across the 12-month measurement. Soil temperature and soil moisture were the major controlling factors of temporal variation of SR in the six sites, while spatial variation in SR was mainly caused by the differences in soil total nitrogen (STN), soil organic carbon (SOC), net photosynthesis rate, and fine root biomass. Our results show that the annual average SR and Q₁₀ (temperature sensitivity of soil respiration) values tended to decrease from secondary forests and grassland to plantations, indicating that the conversion of natural ecosystems to man-made ecosystems may reduce CO₂ emissions and SR temperature sensitivity. Due to the high spatio-temporal variation of SR in our study area, care should be taken when converting secondary forests and grassland to plantations from the point view of accurately quantifying CO₂ emissions via SR at regional scales.     

南水北调中线工程建设与河南水资源可持续利用

文章通过对河南省水资源开发利用现状，存在的主要问题，水资源供需平衡以及南水北调工程对河南省水资源利用的影响论述，提出了在拟定南水北调工程供水方案中，应通过强化节水，加强水资源保护，严格控制地下水开采，将水资源作为商品等措施，促进河南省水资源的可持续开发利用。     

三体散射长钉（TBSS）在C波段雷达中的应用研究

利用普洱CIND3830-CC天气雷达资料、地面观测资料进行统计分析,研究2004-2013年普洱C波段天气雷达中27次三体散射长钉(TBSS)的统计特征、地面降雹与TBSS的对应关系,并对TBSS在冰雹预警方面的应用进行探讨,结果表明:(1)C波段雷达中,产生TBSS的回波的反射率因子范围为55.0~68.4 dBz,70%的TBSS出现在反射率因子≥60 dBz时。(2)TBSS的维持时间为10~79 min,63%的TBSS维持时间超过20 min。(3)TBSS一般出现在4.0~9.5 km,最低出现在2.6 km,最高出现在11.4 km。(4)TBSS长5.6~22.4 km,宽1.5~14.6 km,TBSS宽度与强回波区径向外侧的60 dBz以上回波的面积成正比,但TBSS的长度与反射率因子核心的强度和宽度无明显对应关系。(5)出现TBSS时,59%的回波出现了降雹,11%的回波出现了强冰雹。(6)出现TBSS且出现降雹的过程中,TBSS预报冰雹的时间提前量为5~100 min,平均为34.5 min。(7)在出现TBSS且出现降雹的过程中,TBSS的宽度与冰雹的大小或降雹密度成正比。此外,分析了出现TBSS但未降雹的原因,找出了TBSS配合垂直液态水含量密度(D_(VIL))和45 dBz伸展高度、TBSS配合回波宽度和45 dBz伸展高度的预报冰雹的方法,在出现TBSS特征的回波中,上述方法的预报准确率分别达89%和94%(临界成功指数为0.89和0.94)。     

渭河平原地下水分布特征与环境同位素研究——以白杨水源地为例

白杨水源地座落在渭河下游重镇——渭南市西北约5km处，为渭河冲积平原的一部分。区内第四纪松散堆积物巨厚，地形平坦，降水充沛，地表水丰富，为地下水储存提供了良好的空间。按含水介质的埋藏条件可划分为潜水、浅层承压水、中层承压水和深层承压水4个含水岩组。为了进一步研究地下水的补给形成机制、储存运移过程、排泄开采条件，本文结合环境同位素（包括14C、13C、3H、D和18O）对水源地地下水年龄、地下水运动速率以及一些水文地质参数进行研究和探讨。而同位素测定表明：水源地潜水为现代水，3H含量较高，河水补给量占1/2     

纬向切变基流中的非线性正压Rossby波

在半地转近似下,用相角函数方法得到了包含纬向基流及其切变的非线性常微分方程。利用常微分方程解的拓扑性质的定性理论,直接得到该方程存在有限振幅的周期波解与孤立波解即非线性正压Rossby波解存在的条件,由此分析了纬向切变基流对波解存在的影响。最后利用函数逼近法求得了非线性正压Rossby波解的显式表达式。结果表明,纬向切变基流对波的影响不仅表现在波的存在方面,而且还表现在波的形态方面,反映了波的非线性特点和基流对波动的作用。     

Centrifuge modelling of ground-borne vibrations induced by railway traffic in underground tunnels

Increased attention has been given to ground-borne vibrations induced by railway vehicles and to the effects of these vibrations as they propagate through the ground into nearby buildings.Various studies,mainly based on numerical methods as well as physical modelling,have been carried out to investigate this problem.To study the dynamic response of tunnels and the surrounding soil due to train-induced vibration loads,a centrifuge te st was conducted with a small-scale model in 1 g and 50 g stres...     

An installation system of deepwater risers by an S-lay vessel

Along with the consumption increase of the petroleum products,more countries have transferred their attentions to the offshore fields,especially the deepwater oil and gas reserves.For deepwater exploitation,the risers must be installed to act as the conduits connecting surface platforms to subsea facilities.In this paper,the typical risers sorted by different classes are introduced,and the correspondent installation methods are presented.By investigating the recent projects performed in the deepwater hot spots,and combining the challenges of HYSY201 for riser installation,a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of in the South China Sea.Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of in the South China Sea.     

北京市地面沉降分布及典型灾害类型初探

地面沉降为北京主要次生地质灾害之一,近年来呈现快速发展趋势,对城市规划发展和经济建设的影响日趋明显。目前对于北京地面沉降灾害类型及特征认识较为局限,缺乏全面、系统认识。本文通过区域水准测量监测数据及以往调查资料的搜集整理,结合现场调查,阐明了北京地面沉降分布特征,总结归纳了地面沉降灾害类型及特征,发现区域性地面沉降形成的以井管抬升为代表的点状破坏现象,该类灾害以点为中心呈辐射状分布,影响范围较小。局部差异沉降形成包括墙体开裂、地表开裂及桥梁开裂等具有线状破坏形式的灾害,该类灾害多呈线性沿固定方向延伸,影响范围较大。