Landsat时序数据支持下的藏东南植被时空变化监测     

王华  杨乾鹏  郭山川  旦增  次仁多吉 《测绘通报》2020,(11):7

本文利用GEE平台和1990—2019年巴宜区Landsat遥感影像，采用像元二分模型、相关性分析等方法分析了巴宜区植被覆盖度的时空变化特征与驱动力。研究结果表明：①1990—2019年巴宜区植被覆盖度总体呈稳中有增的趋势，其中，河谷区域增加明显，而高海拔区域相对稳定；②1990—2019年巴宜区气温呈显著升高，降水略有下降，总体呈“暖干化”，气温较降水量对植被覆盖变化更明显，但气候变化对植被覆盖变化影响总体不明显；③1990—2019年巴宜区植被覆盖变化与人类活动有很好的相关性，其中，低、中低、中、中高植被覆盖区域，呈显著的负相关，而高植被覆盖区域呈正相关。本文基于遥感大数据和地理云计算的植被覆盖监测动态监测和定量分析方法，能对高山峡谷区生态评估和演替分析提供一定的技术支撑和科学数据。  相似文献   

基于高斯两步移动搜寻法的村镇避难场所可达性研究     

但文羽  肖映辉  胡周灵  詹庆明 《地球信息科学学报》2018,20(10):1412-1421

避难场所可达性是指避难场所与受灾居民之间的通达性,即灾害发生时,避难人员通过避难疏散通道到达避难场所的难易程度,是评价避难场所布局合理性的重要指标。本研究结合高斯两步移动搜寻法和网络分析法,从供需双向出发对村镇地区避难场所进行可达性分析。2种方法的结合,既充分考虑了需求点与设施点的相互作用,又充分考虑了设施点的吸引力随距离的衰减关系,并基于实际道路,以步行疏散时间作为搜索半径,降低了传统研究中因忽略供需间相互作用及实际距离而引起的可达性结果的误差。最后,以神农架松柏镇区为例,验证该方法的实际应用价值。结果表明,该方法能够有效测定村镇地区避难场所的空间可达性,同时,基于GIS软件可以直观地揭示研究区域内避难场所可达性空间分布差异。该方法可为制定科学的村镇防灾减灾规划提供方法支持。  相似文献   

基于全球分布的地震观测数据估计0S0模态的特征频率及品质因子     

周丰森  王迪晋  旦增 《大地测量与地球动力学》2019,39(10):1013-1016

选取2011-03-11日本MW9.3地震后全球地震台站记录的约220 h波形数据，基于一定的判断准则，筛选出质量较高的448个垂向观测数据，采用频域AR方法对0S0模态的特征频率和品质因子进行估值，并以信噪比为权重进行加权平均，得到特征频率f=0.814 658 4±5.3×10-7，品质因子Q=5 586±12。该结果与已有研究成果相比精度更高，有助于约束现有地球介质密度和衰减模型，使其更接近真实地球。  相似文献   

塔里木盆地塔中地区奥陶系古岩溶包裹体特征及古环境意义     

张庆玉  李景瑞  梁彬  淡永  曹建文 《中国岩溶》2020,39(6):894-899

碳酸盐岩古岩溶型储层是油气勘探开发的重点领域，具有极强的非均质性，是世界级难题。古岩溶发育期次的确定一直都是古岩溶储层地质建模的技术难题。现有判别古岩溶发育期次的方法多以地表裸露古岩溶充填物特征为依据。在塔里木盆地塔中地区地质构造复杂，具有多期次古岩溶作用的叠加改造。本次利用古岩溶充填方解石流体包裹体均一温度法，研究塔中地区奥陶系碳酸盐岩古岩溶作用期次与古环境条件，揭示了4期古岩溶作用环境:加里东期古岩溶作用、海西晚期古岩溶作用、印支-燕山期古岩溶作用、喜马拉雅期古岩溶作用。该研究成果对后期岩溶储层预测具有重要意义。   相似文献   

六盘山区夏秋季大气水汽和液态水特征初步分析     

田磊  桑建人  姚展予  常倬林  单新兰  曹宁  孙艳桥 《气象与环境学报》2019,35(6):28-37

六盘山区是中国典型的农牧交错带和生态脆弱带,也是黄土高原重要的水源涵养地、生态保护区及国家级扶贫开发区。利用2017年6-11月隆德气象站地基多通道微波辐射计资料,结合同期平凉探空站及隆德地面降水等观测资料,分析了六盘山区夏秋季大气水汽、液态水变化特征。结果表明：六盘山区夏秋季在降水天气背景下,大气水汽含量和液态水含量均较高,分别为无降水天气背景下的1.4倍和7.0倍;降水天气背景下水汽在5000 m以下有明显的增加,且在此高度范围内的水汽密度随高度的递减率比无降水天气背景下明显偏小;各高度层的液态水相比无降水天气背景下均有明显增大,除6月外,主峰值均出现在0℃层高度层以下。六盘山区夏秋季各月中,6-9月。大气水汽含量高值区均出现在正午到傍晚时段,低值区均出现在日出前后;液态水含量在日出前、午后及傍晚分别出现峰值,最明显的峰值出现在午后。对一次对流性降水天气过程分析后发现,降水发生前40 min大气水汽含量和液态水含量出现两次明显的跃增,水汽向上输送不断加强,2500-7500 m高度的相对湿度明显增大。  相似文献   

Excess air during aquifer storage and recovery in an arid basin (Las Vegas Valley, USA)     

D. Kip Solomon  Erin Cole  Joseph F. Leising 《Hydrogeology Journal》2011,19(1):187-194

The Las Vegas Valley Water District in Nevada, USA, has operated an artificial recharge (AR) program since 1989. In summer 2001, observations of gas exsolving from tap water prompted a study that revealed total dissolved gas (TDG) pressures approaching 2?atm with a gas composition that it is predominantly air. Measurements of TDG pressure at well heads and in the distribution system indicated two potential mechanisms for elevated TDG pressures: (1) air entrainment during AR operations, and (2) temperature changes between the winter recharge season and the summer withdrawal season. Air entrainment during pumping was investigated by intentionally allowing the forebay (upstream reservoir) of a large pumping station to drawdown to the point of vortex formation. This resulted in up to a 0.7?atm increase in TDG pressure. In general, the solubility of gases in water decreases as the temperature increases. In the Las Vegas Valley, water that acquired a modest amount of dissolved gas during winter artificial recharge operations experienced an increase in dissolved gas pressure (0.04?atm/°C) as the water warmed in the subsurface. A combination of air entrainment during AR operations and its amplification by temperature increase after recharge can account for most of the observed amounts of excess gas at this site.  相似文献   

西藏灌木林种群分布格局     

张超  黄清麟  普布顿珠  旦增 《山地学报》2011,29(1)

以西藏地区370个灌木林标准地调查数据为基础,计算了包括负二项式K值、方差/均值比率t值、丛生指标、平均拥挤指数、聚块性指标、扩散指标、格林指数和Cassic指标,定量测度了各标准地内种群的分布格局类型及集聚强度,分析了西藏灌木种群分布格局随海拔和坡度的变化特征。研究结果表明,1.西藏优势灌木种群分布格局包括集群分布和随机分布两种,其中,随机分布占60%;2.随着海拔及坡度的增加,西藏灌木种群均呈现由集群分布向随机分布变化的趋势,且大部分地区的灌木种群呈随机分布。  相似文献   

新疆地区雪深和雪压的分布及其55年的变化特征分析   总被引：1，自引：0，他引：1  

符传博  丹利  吴涧  魏荣庆 《地球物理学进展》2011,26(1):182-193

本文主要使用新疆地区109个气象站观测资料,对新疆地区雪深和雪压的分布和变化特征以及相关气象因子进行了系统分析,结果表明:新疆地区的积雪多年平均表现为北部多于南部,其中雪深和雪压最大值出现在新疆北部,数值分别为10 cm和10g/cm2.新疆积雪的季节特征较为明显,其中2月份积雪最大,雪深和雪压分别为9.2 cm和5....  相似文献   

Testing resilience thinking in a poverty context: Experience from the Niger River basin     

Christophe Béné  Louisa Evans  David Mills  Solomon Ovie  Aminu Raji  Ahmadu Tafida  Amaga Kodio  Famory Sinaba  Pierre Morand  Jacques Lemoalle  Neil Andrew 《Global Environmental Change》2011,21(4):1173-1184

Resilience thinking is an important addition to the range of frameworks and approaches that can be used to understand and manage complex social–ecological systems like small-scale fisheries. However, it is yet to lead to better environmental or development outcomes for fisheries stakeholders in terms of food security, improved livelihoods and ecological sustainability. This paper takes an empirical approach by focusing on the fundamentals of resilience thinking to evaluate its usefulness in developing relevant management interventions in small-scale fisheries in the Niger River Basin in West Africa. The paper presents the outputs of a participatory assessment exercise where both fishery communities and local experts were involved at two different scales. The resilience frame used was designed to facilitate the identification of socially defined thresholds that help delineate the desirability of the current system configuration and provides a diagnosis framework that tailors management solutions to problems in local context. The analysis highlights some key contributions from resilience thinking to the challenge of diagnosis in small-scale fisheries management in developing countries, as well as important contributions that emerge from taking a pragmatic and critical approach to its application.  相似文献   

Analysis of seismic noise in the Romanian-Bulgarian cross-border region     

Bogdan Grecu  Cristian Neagoe  Dragos Tataru  Felix Borleanu  Bogdan Zaharia 《Journal of Seismology》2018,22(5):1275-1292

We present the first detailed investigation of the background seismic noise recorded in the Romanian-Bulgarian cross-border region over 3 years (2012–2015). We used the power spectral densities probability density functions (PSD PDFs) to study the noise variations in the period domain (0.025–1 s) as well as in the secondary microseism band (2–10 s). Strong diurnal variations and an increase of the noise levels during working days were observed at high frequencies at all stations, thus confirming the anthropic origin of the noise at low periods. The noise variations observed at longer periods (>?1 s) are relatively small among the stations and are related to season changes. The dominant feature in the noise spectra between 2 and 10 s is the double-frequency peak (DFP) whose amplitude increases and changes during winter. For a specific interval, from 25th to 27th of January 2014, when a storm was reported in the Black Sea area, the maximum of the DFP shifted from larger periods (~?5.5 s) at stations far from the Black Sea towards smaller periods (~?1.8 s) at stations located on the coastline. The polarization analysis showed that the short period double-frequency microseisms originating from the Black Sea dominate during the winter month. Finally, we showed that site conditions vary due to noise variations related to weather conditions in the Black Sea or to changes in anthropogenic noise sources.  相似文献