黄河入海径流量周期变化与东亚夏季风的关系研究

为揭示近 70 年东亚夏季风与黄河夏季入海径流量的多尺度特征以及二者之间的响应关系,本文利用集合经验模态分解 （EEMD） 和小波分析对二者的多尺度特征进行研究,利用交叉小波分析和小波相干性等方法对东亚夏季风和黄河夏季入海径流量在时频域内的共振周期以及相干性进行探究。结果表明：东亚夏季风具有显著的年际、年代际尺度特征,且以年际周期振荡最为显著,其中,2.7 a 左右的周期尺度对东亚夏季风的整体影响程度最高,另外,40 a 左右的年代际周期亦具有较强显著性。黄河夏季入海径流量的年际、年代际尺度周期均通过了 80 %的显著性检验,且以 2.1 a 左右的年际周期为主。东亚夏季风与黄河夏季入海径流量的交叉小波功率谱显示二者在 2 a、6~7 a 左右具有显著的共振周期,且在 1980— 1990 年之间通过了 95 %的显著性检验,由二者的小波相干谱发现,东亚夏季风和径流量的显著性在低能量区大于高能量区,且东亚夏季风提前径流量约 1/4 个周期,另外,1980—2000 年之间在 6~7 a 左右周期尺度上二者的相干性极强。该研究可为黄河下游水资源管理及预测提供一定的理论依据。     

基于自动站资料的近15年北京地区舒适度变化特征

利用44个自动站的小时观测资料,详细分析了北京地区近15年来气温、风速、相对湿度和有效温度的分布和变化情况,结果表明：1）北京地区年平均气温、风速和有效温度都显著地受到了地形分布的影响,相对湿度没有表现出明显的地形差异。研究时段内,北京整体呈变干变暖。区域上,气温与有效温度增幅最大的区域集中在平原中心城区,西北和东北部的远郊山区增幅最小,相对湿度降低的程度在区域上较为平均;2）按有效温度的热感受等级划分,北京地区冬季平均热感受属于“寒冷”,年、春季和秋季平均热感受属于“冷”,夏季平均热感受属于“温暖”。春季、夏季和冬季变干变暖明显,秋季则存在明显的区域差异;3）北京地区年平均气候适宜日数在全年中占比41.3%。气候适宜日数变化在区域间差异较大,超过半数站点表现出“气候适宜日数”的减少。由于整体上的变干变暖趋势,导致春季“气候适宜日数”整体在增加,夏季“气候适宜日数”整体在减少。秋季的“气候适宜日数”没有表现出统一的趋势。冬季的热感受主要集中于寒冷日和冷日,“气候适宜日数”很少。     

Characteristics of ground motion at permafrost sites along the Qinghai-Tibet railway

Based on 14 typical drilling holes distributed in the permafrost areas along the Qinghai-Tibet railway, the distribution of wave velocities of soils in the permafrost regions were determined. Using results of dynamic triaxial tests, the results of dynamic triaxiality test and time histories of ground motion acceleration in this area, characteristics of ground motion response were analyzed for these permafrost sites for time histories of ground accelerations with three exceedance probabilities (63%, 10% and 2%). The influence of ground temperature on the seismic displacement, velocity, acceleration and response spectrum on the surface of permafrost were also studied.     

甘肃省土坯房空间分布特征与多因素分类方法研究

通过对甘肃省土坯房的不同地区现场调查,获取了大量的基础数据资料,经过分类整理和分析研究,取得了以下主要结果:(1)按照承重方式的不同,土坯房可分为墙体承重、砖柱(木柱)承重和混合承重3个类型,并给出了其在甘肃省的空间分布特征;(2)讨论了对土坯房震害影响最大的地震动特性、场地条件、结构类型等几个因素;(3)结合2003年甘肃省民乐-山丹6.1级地震、岷县-临潭-卓尼5.2级地震以及2008年汶川8.0级地震中土坯房的震害表现,在土坯房分类基本原则的基础上,提出了甘肃省土坯房多因素分类方法,并给出了针对现有土坯房的评定准则,通过准则能够获知目前甘肃省土坯房现状及其防御地震能力的综合评价信息。     

Response of runoff in the headwater region of the Yellow River to climate change and its sensitivity analysis

Response of the runoff in the headwater region of the Yellow River to climate change and its sensibility are analyzed based on the measured data at the four hydrological stations and ten weather stations during the period 1959-2008. The result indicates that change of temperature in the region has an obvious corresponding relationship with global warming and the changes of annual average temperature in each subregion in the region have been presenting a fluctuant and rising state in the past 50 years. However the change of precipitation is more intricate than the change of temperature in the region because of the influences of the different geographical positions and environments in various areas, and the change of annual precipitation in the main runoff-producing area has been presenting a fluctuant and decreasing state in the past 50 years. And there is a remarkable nonlinear correlativity between runoff and precipitation and temperature in the region. The runoff in the region has been decreasing continuously since 1990 because the precipitation in the main runoff- producing area obviously decreases and the annual average temperature continuously rises. As a whole, the runoff in each subregion of the headwater region of the Yellow River is quite sensitive to precipitation change, while the runoff in the subregion above Jimai is more sensitive to temperature change than that in the others in the region, correspondingly.     

地下水水位预测在深基坑工程中的应用

通过地下水水位预测,能够确定从降水井合笼到基坑开挖时的日期,开挖速度,可调整降水井的布局,确定最佳降水方案。结合工程实例,阐述地下水水位预测在基坑降水方案设计中的应用,具有较好的实用价值。     

岩溶地区公路路坡重金属污染垂向变化特征研究

随着公路交通业的发展,汽车尾气对周围环境的影响也越来越大,公路边坡污染问题也越来越受重视。对于岩溶区路侧的横向污染变化,在其它文献中已有报到,本文着重研究岩溶地区路坡垂向上汽车尾气的重金属污染。文章以贵新路为例,分析了公路边坡土壤重金属污染物的垂向污染状况和变化规律,得出了路坡重金属污染的富集带约分布在距地面5m处,随着高度的增加污染物含量减少,但到了路坡坡顶又出现小幅增高现象,这有可能与汽车尾气卷扬和淀积效应有关。      

河北省阳原盆地井儿洼钻孔磁化率、粒度反映的环境意义

根据河北省阳原盆地井儿洼钻孔岩芯湖相沉积物的粒度特征,划分出大约0.2Ma以来,井儿洼地区经历了湖沼-浅湖-滨浅湖-滨湖的演化过程,其中至少存在8个高-低水位变化旋回。湖泊不同的演化阶段应用不同的粒级颗粒含量来作为环境指标。在滨湖环境下,50~100μm,>50μm及中值粒径具有良好的环境指示意义;浅湖环境中,<5μm或2~50μm的细颗粒是较好的指标。不同的沉积相中,磁化率的强度与分粒级颗粒含量的相关性不同:滨-浅湖相中磁化率强度与粗粒沉积物呈正相关;湖滨沼泽相中磁化率强度与细粒含量呈正相关;咸化滨湖中磁化率与粒度基本不相关。      

基于强度折减概念的滑坡稳定性三维分析方法(I)：滑带土抗剪强度参数反演分析

滑带土抗剪强度是滑坡稳定性分析和防治工程设计中十分重要而又难于确定的参数之一。因此,基于临界状态假定的二维反分析方法得到了广泛应用。但是,自然界发生的滑坡基本上呈三维形态,其主滑方向有时变化也较大,使得有必要研究一种滑带土抗剪强度的三维反分析方法和滑坡稳定性的三维评价方法。笔者建议了一种基于强度折减概念的滑带土抗剪强度反分析方法,即通过逐步折减滑动面的强度参数,使滑动面的塑性区完全贯通,此时,塌滑体处于极限状态,所用强度参数即为滑带土的平均抗剪强度参数。从洪家渡水电站1#塌滑体计算成果来看,反演的滑带土摩擦角较二维反演值低4.1?,反映了滑坡体的三维效应,验证了所建议方法的可行性。     

An improved method for estimating forest canopy height using ICESat-GLAS full waveform data over sloping terrain: A case study in Changbai mountains,China

Light Detection And Ranging (LiDAR) has a unique capability for estimating forest canopy height, which has a direct relationship with, and can provide better understanding of the aboveground forest carbon storage. The full waveform data of the large-footprint LiDAR Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat), combined with field measurements of forest canopy height, were employed to achieve improved estimates of forest canopy height over sloping terrain in the Changbai mountains region, China. With analyzing ground-truth experiments, the study proposed an improved model over Lefsky's model to predict maximum canopy height using the logarithmic transformation of waveform extent and elevation change as independent variables. While Lefsky's model explained 8–89% of maximum canopy height variation in the study area, the improved model explained 56–92% of variation within the 0–30° terrain slope category. The results reveal that the improved model can reduce the mixed effects caused by both sloping terrain and rough land surface, and make a significant improvement for accurately estimating maximum canopy height over sloping terrain.