基于图像阈值法的森林雪灾损失遥感估测——以云南省为例   总被引：1，自引：1，他引：0  

吴健生  陈莎  彭建 《地理科学进展》2013,32(6):913-923

雪灾是森林生态系统的严重生态干扰之一, 会严重影响林木生长并降低生态系统功能。利用2000-2011年SPOT NDVI长时间序列影像数据, 基于SG滤波函数进行时序重建, 采用灾后同期影像的图像阈值法, 以常年多灾的云南省2008 年雪灾为例, 进行雪灾森林植被受损评估。评估结果与全国灾情月报中的云南省雪灾范围基本一致, 全省森林雪灾受损面积达12.09%, 主要分布在滇西北的迪庆州、怒江州。对森林雪灾受损程度分析表明, 全省重度受灾县7 个, 中度受灾县13 个, 轻度受灾县45 个。对海拔、坡度、坡向、坡位等地形条件的叠加分析表明, 海拔3300~4000 m、坡度5~15°、处于东坡或东北坡中坡位的森林植被受损最严重。本研究有助于实现森林雪灾损失的快速评估, 对有效规避次生灾害、开展灾后恢复重建规划具有重要意义。  相似文献   

黄河水下三角洲浅表土体的风暴液化问题探讨     

许国辉  孙永福  于月倩  林霖  胡光海  赵庆鹏  郭秀军 《海洋通报(英文版)》2012,14(1):80-89

黄河水下三角洲的地质勘察揭示了海底浅表地层发生的各种灾害地质现象。本文以风暴浪导致海底土体液化观点,结合土体动力三轴试验、波浪水槽试验,对黄河水下三角洲浅表地层土体的液化发生条件、形成模式、液化土体运动以及地层发生的重新层化问题进行了分析,指出黄河水下三角洲的灾害地质由于风暴浪导致海底粉质土液化运动而形成,液化后土体运动形式与波浪运动一致,液化土体运动造成的土颗粒分异而使地层重新层化,并初步指出了风暴浪导致海底土体液化在地学、环境、工程等方面的研究问题。  相似文献   

温州近岸围堤对风暴潮漫滩影响的数值研究     

吴玮  傅赐福  于福江  刘秋兴 《海洋学研究》2012,30(2):36-42

利用-套基于非结构网格且能计算海水漫堤溢流的超高分辨率风暴潮漫滩数值模式模拟由9417号台风特大风暴潮引起的漫滩,结果与实测吻合良好。此外,选取超强台风强度并以9417台风路径为南路径,往北每间隔30 km为中路径和北路径设计了3条台风路径,进行了-系列数值模拟得出:近岸围堤加大了风暴潮、漫滩淹没对温州的威胁,而且由南路径引起的漫滩深度和中路径引起的漫滩面积影响最大。究其原因,近岸围堤对外海风暴潮在温州近海及瓯江口传播的阻隔和分流作用,两者综合变相加大了风暴潮往瓯江口北侧海域、瓯江北口、瓯江中上游的输送量。  相似文献   

风暴潮对广东省沿海港航设施影响及防护对策研究     

贾良文  谢凌峰  罗敬思  徐治中  龚文平 《海岸工程》2012,(3):55-64

通过实地调研,结合历史记录资料,初步研究了风暴潮对广东省沿海港航设施的影响状况和特点,提出了相应的防护措施。研究发现,广东省沿海港口设施受风暴潮影响的主要特点为防波堤受损最为严重,施工期受风暴潮影响损坏普遍存在,码头护岸受损较普遍,大型码头结构受损较少,中、小型码头结构特别是渔港结构受损较多。损坏成因主要包括波浪基础资料不足、设计波浪偏低、护面块体偏小等。从技术、工程和管理三个方面提出了防护措施。技术措施主要为加强波浪观测和科学研究;改进设计波浪推算方法。工程措施包括适当提高设计波浪标准;适当提高护面块体标准;优化平面布置,缩短无防护施工期;设立安全岛和避险安全区;加强对已建港航设施的现状调查、复核和分析,采取针对性的加固措施等。管理措施包括设立沿海港口风暴潮预警预报系统;编制风暴潮应急预案;加强港航设施的维护等。  相似文献   

QuikSCAT风场在台风风暴潮计算中的应用   总被引：1，自引：0，他引：1  

付翔  仉天宇  于福江 《海洋预报》2012,29(4):18-22

业务化风暴潮计算中多采用模型风场的算法来给出风暴潮强迫场。最大风速半径是模型风场最难确定的参数之一。利用QuikSCAT卫星风场数据拟合台风最大风速半径是确定该参数的有效方法。将拟合得到的最大风速半径代入模型风场计算风暴潮的驱动场,模拟的沿岸风暴增水与实况更为接近。  相似文献   

辽东东探区温带气旋风暴减水重现值估计     

董胜  周冲  陈同彦 《中国海洋大学学报(自然科学版)》2012,(Z2):150-155

基于辽东东探区1966—2007年出现的76次温带气旋减水过程,对10个工程地点抽取了10个统计样本。考虑每年温带气旋出现频次的影响,使用泊松最大熵分布对其进行减水的长期统计分析。得到100年一遇和50年一遇最大幅度的减水重现值分别为304和286cm。由于受地形的影响,北部海域的减水幅度大于南部区域。  相似文献   

2004年11月7-8日巨磁暴期间场向电流的分布特征          下载免费PDF全文

刘晓灿  陈化然  杜爱民  王源 《地球物理学报》2012,55(7):2153-2161

利用CHAMP卫星磁场数据分析研究了2004年11月7日至8日巨磁暴(Dst<-200 nT)期间大尺度场向电流的分布特征.把方向相同且时间连续的一段场向电流定义为一个电流片,分析结果表明,伴随磁暴的发展,在卫星飞过的两个扇区(早上扇区0200-0400MLT及下午扇区1400-1600MLT)中的大尺度场向电流分布呈现不同的纬向分布特征:随着地磁扰动的增强,早上扇区电流片分布范围向高纬扩展;而下午扇区电流片分布范围则显著地向低纬扩展.与地磁活动SYM-H和AE指数对比分析得出,早上扇区的大尺度电流片的分布特征更多地受到亚暴活动的影响,而下午扇区的电流片分布则明显反映出磁暴环电流活动的特征.  相似文献   

Sequence polymorphism in a marine bivalve (Perna canaliculus) orphan G protein‐coupled receptor gene: Preliminary description and possible implications     

Andrew E. Fidler  Helgi B. Schiöth  Robert Fredriksson 《新西兰海洋与淡水研究杂志》2013,47(4):953-964

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Spatial and temporal distribution of storms and their activities over the Bay of Bengal     

Xu Duan  Yun Tao  CanQiong Cun  ShiChang Guo  LinYi LV 《寒旱区科学》2009,1(5):0448-0457

By statistically analyzing the storm data from the Joint Typhoon Warning Center(JTWC) over the Bengal Bay during the period 1945-2006,it is found that the yearly averaged tropical cyclone(TC) number over the Bay of Bengal is 8.12,which takes place in any month of the whole year;February and March have the fewest TC numbers.The TC numbers begin to increase starting in April and arrive at a peak in October.Differing from TC over the Bay of Bengal,the tropical storms(TS) over the Bay of Bengal has two peak periods,appear in May and in October or November,respectively.With regard to TS intensity,the super severe storm of H4 criterion appeared only one time during the period 1971-1986,but appeared eight times during the period 1987-2006.The monthly change of the original position,the averaged maintaining time,and the longest maintaining time of TS also have two peak values:They appear in April or May and in October or November,respectively.The peak value of the original position in October or November is bigger than that in April or May.The peak value of the average maintaining time and the longest main-taining time of the TS in April or May is bigger than that in October or November.TC landfall path is mostly moving toward northwest or west and accounts for 56.7 percent.The landfall path of the TS differs from that of TC in some respects.The main difference is that the numbers of the northwestern path and un-landfall of TS are less than those for TC,and the numbers of the western path and northeastern path of TS are greater than for TC.Because of the landfall TS in the north-east path has a peak,it and the beginning of the rainy season in Yunnan Province are closely related;it is on Yunnan Province’s early summer precipita-tion that they have a great impact.  相似文献   

Temporal and spatial behaviour of rip channels in a multiple‐barred coastal system     

S. Quartel 《地球表面变化过程与地形》2009,34(2):163-176

A 15‐month data set of daily time‐averaged video images (Argus) has been analyzed to describe the spatial and temporal variability of the rip channels on a multiple‐barred coast at Noordwijk aan Zee, The Netherlands. The landward boundary of the intertidal bars and a proxy of the subtidal bar crest, defined as the intertidal and subtidal bar lines respectively, were derived from the Argus images. Local seaward‐directed deviations of the bar lines represent the cross‐shore and alongshore locations of the rip channels. The average intertidal rip spacing ( ) was 243 m, but the rips were not spaced regularly (σ_λ/ = 0.47). Some intertidal rips were observed to fill up during falling tide, but the majority remained open. The filled intertidal rip channels had more landward positions and migrated more slowly (2.4 versus 4.6 m/day) in the alongshore direction than the open intertidal rip channels. The number and the alongshore migration rate of open intertidal rip channels increased with the preceding wave heights (r = 0.26, p < 0.01) and alongshore component of the offshore wave power (r = 0.25, p < 0.01), respectively. The shape of the intertidal bar lines was similar to the subtidal bar line shape, suggesting that the intertidal morphology is coupled to the subtidal alongshore variability. The phase of two bar lines could vary from in phase (0°) to out of phase (180°). The phase changes gradually, due to different alongshore migration rates of the intertidal and subtidal bar lines. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献