波粒相互作用导致环电流质子沉降的卫星共轭观测          下载免费PDF全文

王杰  袁志刚  余雄东  薛祖祥 《地球物理学报》2020,63(6):2131-2140

波粒相互作用是环电流损失的重要机制之一,但波粒相互作用导致的环电流离子沉降而损失迄今为止缺乏直接的观测证据.基于磁层及电离层卫星的协同观测,本文报道了发生在2015年9月7日,由电磁离子回旋波(EMIC波)导致环电流质子沉降的共轭观测事件.在等离子体层的内边界,Van Allen Probe B卫星观测到,存在EMIC波的区域和不存在EMIC波的区域相比,离子通量的投掷角分布的各向异性变弱.我们将Van Allen Probe B卫星沿着磁力线投影到电离层高度,同时在该投影区域内DMSP 16卫星在亚极光区域观测到环电流质子沉降.而且,通过从理论上计算质子弹跳平均扩散系数,我们进一步证实观测的EMIC波确实能将环电流质子散射到损失锥中.本文的研究工作为EMIC波导致环电流质子沉降提供了直接的观测证据,揭示了环电流衰减的重要物理机制:EMIC波将环电流质子散射到损失锥中,从而沉降到低高度大气层中而损失.  相似文献   

BDS卫星钟差半参数平差模型异常数据探测与处理     

李文涛  颜雄  夏磊  任青阳  陈洁  潘雄 《测绘学报》2020,49(1):55-64

针对北斗卫星钟差数据中出现钟跳、粗差等异常数据频次较高的问题,将半参数平差模型引入BDS的钟差数据的处理过程中。首先,在考虑系统误差的同时,改进了常用的钟差模型;其次,综合考虑异常数据和系统误差,利用补偿最小二乘原理和极值求解方法,详细推导了分离异常数据前后参数和非参数估计值与相应观测值改正数的关系表达式,实现了异常数据的定值、参数求解和系统误差分离。在此基础上,引入Cook距离,给出了利用参数分量和非参数分量的Cook距离及混合Cook距离,去判断异常值的位置,并给出了一些参数的选取方法及相应的处理措施,实现了卫星钟差异常数据的定位和定值以及部分系统误差的分离。最后,采用武汉大学GNSS中心提供的采样间隔为5 min的北斗卫星精密钟差数据,将本文方法与常用方法进行了试验对比。试验结果表明,本文方法能够有效地识别并处理卫星钟差数据中的异常值,有效克服了基于经验阈值钟差异常数据探测方法的不足,且该方法对于量级较小的异常钟差数据也有很好的探测效果,一定程度丰富了现有的BDS钟差数据质量控制方法。  相似文献   

广西土壤有机质空间变异特征及其影响因素研究   总被引：2，自引：0，他引：2  

钟聪  李小洁  何园燕  邱微文  李杰  张新英  胡宝清 《地理科学》2020,40(3):478-485

基于广西第二次土壤普查的270个土壤剖面资料,结合1∶50万数字化土壤类型图、土地利用类型图和气象监测数据等资料,利用地统计学和逐步回归分析等方法对广西表层土壤有机质空间变异特征及其影响因素进行了探究。结果表明：广西表层土壤有机质平均含量为3.11±2.19%,变异系数为70.72%,空间分布呈北高南低的趋势。广西表层土壤有机质空间分布受到自然和人为因素的共同影响,土壤类型、成土母质、海拔、土地利用、气候和坡度6个环境因子对全区土壤有机质含量变异的综合解释能力为47.9%。其中,土壤类型是最重要的影响因素,能独立解释其变异的36.0%,海拔和成土母质分别能独立解释28.5%和15.8%。气温对广西土壤有机质空间分布的影响比降水量更加显著,从而造成了广西土壤有机质整体呈南低北高的趋势。同时,土壤有机质对气温的敏感性在一定程度上受到降雨量的制约。此外,研究区农业耕作管理等因素对土壤有机质的影响也不容忽视。  相似文献   

景电灌区移民对祁连山植被恢复的相对生态价值          下载免费PDF全文

赵建林  康德奎  彭维恩  王建礼  史中兴  陈天顺  董志洋  汪杰  常兆丰 《干旱区地理》2020,43(1):182-189

近些年来，生态系统的服务价值研究已成为生态学以及生态经济学领域中的一个热点问题。祁连山被称为伸进西北干旱区的一座湿岛，在我国“一带一路”建设中占有重要地位。景电灌区兴建以来从祁连山移出了大量农牧民。那么，景电灌区移民对祁连山植被恢复的生态价值如何呢？以景电灌区移民涉及到的祁连山东端景泰、古浪、天祝3县山区为研究区，用价值工程方法对从祁连山区向景电灌区移民退耕退牧还林还草的生态价值做了分析，并与模型因子当量法的计算结果进行了比较。结果表明：祁连山向景电灌区移民退耕退牧还林还草总的生态价值为37.458 1×10⁸元。其中，退耕还林还草的生态价值为37.438 6×0⁸元，退牧后草场植被盖度增加的生态价值为194.79×104元。计算结果为用COSTANZA和谢高地模型因子当量法计算得的祁连山向景电灌区移民退耕退牧还林还草总的生态服务价值40.054 0×0⁸元的93.52%。两种方法计算结果祁连山向景电灌区移民退耕退牧还林还草总的生态价值为景电工程年总成本1.45×0⁸元的25.8~27.6倍。两种计算结果一致表明，景电灌区生态移民对祁连山植被恢复的生态价值十分突出。由此也可以看出，COSTANZA和谢高地模型因子当量法适用于祁连山的生态服务价值分析。  相似文献   

游客-环境互动视角下旅游者目的地环境恢复性效应     

朱芳  苏勤  陶云  沈惊宏 《热带地理》2020,40(4):636-648

日常生活环境和旅游目的地环境都可以为个体提供恢复的机会，不同环境的属性特征导致不同程度的恢复。为了探究环境类型与恢复性效应之间的关系及停留时间的调节作用，文章采用问卷调查方式，利用配对样本t检验和混合设计方差分析相结合的方法，探讨游客在不同环境中的恢复性效应，并对这一现象提供心理上的解释。结果表明：1）恢复体验的4个维度（放松体验、心理脱离、掌握体验、控制体验）在旅游目的地环境中的得分均高于日常生活环境。2）掌握和控制体验维度在城市旅游目的地中的变化程度高于乡村旅游目的地，两种类型目的地的放松和心理脱离维度差异较小。3）随着在目的地停留时间的延长，乡村旅游目的地放松体验和心理脱离维度变化程度高于城市旅游目的地，两种类型目的地环境恢复性效应会相互靠近。因此，游客的环境恢复性效应不仅受到环境和目的地类型的影响，同时还与游客的适应程度有关，且受到其停留时间的调节作用。  相似文献   

Post-earthquake economic resilience and recovery efficiency in the border areas of the Tibetan Plateau: A case study of areas affected by the Wenchuan Ms 8.0 Earthquake in Sichuan,China in 2008     

Zhou  Kan  Liu  Baoyin  Fan  Jie 《地理学报(英文版)》2020,30(8):1363-1381

Journal of Geographical Sciences - The border areas of the Tibetan Plateau and the neighboring mountainous areas have a high incidence of earthquakes with a magnitude greater than Ms 5.0, as well...  相似文献   

3D Mineral Prospectivity Mapping with Random Forests: A Case Study of Tongling,Anhui, China     

Xiang  Jie  Xiao  Keyan  Carranza  Emmanuel John M.  Chen  Jianping  Li  Shi 《Natural Resources Research》2020,29(1):395-414

Natural Resources Research - In the past few decades, a variety of data-driven predictive modeling techniques has led to a dramatic advancement in mineral prospectivity mapping (MPM). The random...  相似文献   

气候变化下基于物种与植物耦联机制的小白额雁(Anser erythropus)潜在生境及适宜性研究--以长江流域中下游为例     

向伶  高翔  彭玉辉  梁婕 《资源与生态学报(英文版)》2020,11(2):140-149

气候变化和人类活动通过改变物种生境而影响物种多样性。小白额雁是长江流域中下游的一种具有较高生态价值的食草型濒危候鸟,受气候变化和人类活动威胁。本文以小白额雁为代表性物种,定量分析了气候变化对长江流域中下游候鸟潜在生境及适宜性空间分布格局的影响。采用Maxent模型模拟了当前情景和全球环流模型(GCMs)气候场景下小白额雁潜在生境及其适宜性分布。研究结果表明,小白额雁分布特征与其栖息地周边植物分布呈显著相关关系;运用Maxent模型模拟小白额雁六种主要食源植物的分布特征,并将其结果作为环境变量,将显著改善小白额雁潜在生境及其适宜性模型的模拟性能;在两种典型浓度情景(RCP 2.6和RCP8.5)下,2070年小白额雁潜在生境适宜性面积将下降。为应对气候变化对小白额雁的影响,应采取更加合理的管理措施和保护政策,包括调整保护区的大小、形状和用途。  相似文献   

Modeling lateral circulation and its influence on the along-channel flow in a branched estuary     

Lei Zhu  Qing He  Jian Shen 《Ocean Dynamics》2018,68(2):177-191

A numerical modeling study of the influence of the lateral flow on the estuarine exchange flow was conducted in the north passage of the Changjiang estuary. The lateral flows show substantial variabilities within a flood-ebb tidal cycle. The strong lateral flow occurring during flood tide is caused primarily by the unique cross-shoal flow that induces a strong northward (looking upstream) barotropic force near the surface and advects saltier water toward the northern part of the channel, resulting in a southward baroclinic force caused by the lateral density gradient. Thus, a two-layer structure of lateral flows is produced during the flood tide. The lateral flows are vigorous near the flood slack and the magnitude can exceed that of the along-channel tidal flow during that period. The strong vertical shear of the lateral flows and the salinity gradient in lateral direction generate lateral tidal straining, which are out of phase with the along-channel tidal straining. Consequently, stratification is enhanced at the early stage of the ebb tide. In contrast, strong along-channel straining is apparent during the late ebb tide. The vertical mixing disrupts the vertical density gradient, thus suppressing stratification. The impact of lateral straining on stratification during spring tide is more pronounced than that of along-channel straining during late flood and early ebb tides. The momentum balance along the estuary suggests that lateral flow can augment the residual exchange flow. The advection of lateral flows brings low-energy water from the shoal to the deep channel during the flood tide, whereas the energetic water is moved to the shoal via lateral advection during the ebb tide. The impact of lateral flow on estuarine circulation of this multiple-channel estuary is different from single-channel estuary. A model simulation by blocking the cross-shoal flow shows that the magnitudes of lateral flows and tidal straining are reduced. Moreover, the reduced lateral tidal straining results in a decrease in vertical stratification from the late flood to early ebb tides during the spring tide. By contrast, the along-channel tidal straining becomes dominant. The model results illustrate the important dynamic linkage between lateral flows and estuarine dynamics in the Changjiang estuary.  相似文献   

Morphological and molecular diagnoses of Polydora brevipalpa Zachs,1933(Annelida: Spionidae) from the shellfish along the coast of China     

YE Lingtong  YAO Tuo  WU Lin  LU Jie  WANG Jiangyong 《中国海洋湖沼学报》2019,(2)

Shell-boring species Polydora brevipalpa Zachs, 1933 is redescribed based on morphological observations and molecular approach for future unambiguous identification. Genetic distance analyses showed that the interspecific polydorid variation(16.7%–25.6%) was at least 15 times higher than the intraspecific one(0.2%–0.9%) based on the cytochrome c oxidase subunit I(CO1) gene sequences of polydorids. However, 18 S rDNA variation pattern demonstrated a rather narrow barcoding gap, with the interspecific polydorid variation(0.5%–5.6%) being very close to the intraspecific one(0.0%–0.4%). As such, the CO1 gene exhibited better DNA barcode for identification of polydorids than the 18 S rDNA gene because of the su ciently large barcoding gaps. Analysis of molecular variance results based on CO1 gene sequences showed that most variations in sequences(97.79%) lay within groups of adult worms and egg capsules rather than between them. This indicated that egg capsules from Crassostrea gigas(Thunberg,1793) in Ningbo and Nantong were related to the adult worms from Patinopecten yessoensis(Jay, 1857) in Dalian, and both of them belonged to P. brevipalpa. This result was further supported by parsimony network analysis, which showed that egg capsules collected from dif ferent localities and adult worms shared a single haplotype. This study was the first to report both P. brevipalpa infestation on C. gigas and to utilise the known CO1 sequences of the adult polydorids to validate morphologically unidentified egg capsules or early larvae. P. brevipalpa was most possibly brought to Chinese waters through transportation of Pa. yessoensis brood stock from Japan.  相似文献