退耕还林还草工程对中国北方农牧交错区土地利用/覆被变化的影响——以科尔沁左翼后旗为例   总被引：6，自引：0，他引：6  

周德成  赵淑清  朱超 《地理科学》2012,(4):442-449

以北方农牧交错区-科尔沁左翼后旗为例,利用卫星遥感技术获取1980~2010年土地利用/覆被信息,通过统计模型重建土地利用/覆被及景观格局变化过程,综合评价二者动态及退耕还林还草等生态恢复工程的影响。研究区土地整体处于准平衡态势,各地类双向转换较频繁;耕地与草地的变化对区域土地利用/覆被及景观格局变化起支配作用;退耕还林还草等生态恢复工程逆转了天然植被(包括草地与林地)整体减少及耕地与未利用地增加的局面,使各景观破碎化程度有所缓解,这可能有利于生态环境的改善。  相似文献   

A synergic algorithm for retrieval of aerosol optical depth over land     

郭建平  薛勇  曹春香  张颢  光洁  张小曳  李小文 《大气科学进展》2009,26(5):973-983

In this paper, a novel algorithm for aerosol optical depth(AOD) retrieval with a 1 km spatial resolution over land is presented using the Advanced Along Track Scanning Radiometer (AATSR) dual-view capability at 0.55, 0.66 and 0.87 μm, in combination with the Bi-directional Reflectance Distribution Function (BRDF) model, a product of the Moderate Resolution Imaging Spectroradiometer (MODIS). The BRDF characteristics of the land surface, i.e. prior input parameters for this algorithm, are computed by extracti...  相似文献   

纬向平均的风向改变指数与季节转换     

朱敏  张铭  徐建霞 《热带气象学报》2010,26(1):86-92

通过定义一个能客观定量描述大气环流四维时空变化的风向改变指数WI,用以研究大气环流的时空演变规律和季节转换。在对纬向平均的WI做了经验正交函数(EOF)分析后,得到了其前四个模态。第一模态揭示的是全年平均的WI空间分布的基态。第二模态反映的是WI场的偏差中呈现准调和变化的部分,热带、副热带、温寒带季风区在该模态中均有明显体现。第三模态反映的是WI场的偏差中呈现非调和变化的部分,该部分揭示了因南北半球海陆分布的差异和因大气、海洋流体的非线性效应,其所造成的从春到秋与从秋到春的季节变化的不对称性以及平流层的二月突变现象。第四模态反映的是全球各层盛行风反向区域从春到夏的北进和从夏到秋南撤的现象。  相似文献   

An analytical approach to small amplitude solutions of the extended nearly circular Sitnikov problem     

J. Hagel 《Celestial Mechanics and Dynamical Astronomy》2009,103(3):251-266

The model of extended Sitnikov Problem contains two equally heavy bodies of mass m moving on two symmetrical orbits w.r.t the centre of gravity. A third body of equal mass m moves along a line z perpendicular to the primaries plane, intersecting it at the centre of gravity. For sufficiently small distance from the primaries plane the third body describes an oscillatory motion around it. The motion of the three bodies is described by a coupled system of second order differential equations for the radial distance of the primaries r and the third mass oscillation z. This problem which is dealt with for zero initial eccentricity of the primaries motion, is generally non integrable and therefore represents an interesting dynamical system for advanced perturbative methods. In the present paper we use an original method of rewriting the coupled system of equations as a function iteration in such a way as to decouple the two equations at any iteration step. The decoupled equations are then solved by classical perturbation methods. A prove of local convergence of the function iteration method is given and the iterations are carried out to order 1 in r and to order 2 in z. For small values of the initial oscillation amplitude of the third mass we obtain results in very good agreement to numerically obtained solutions.  相似文献   

遥感图像空间分辨率改进值计算方法     

郭从洲  赖广陵  童晓冲  丁璐 《测绘科学技术学报》2017,34(1)

为了克服超分辨重建后的遥感图像空间分辨率的界定还采用人工对比判读存在误差和结论不统一的缺点,利用调制传递函数、奈奎斯特采样定理和人眼极限频率,建立了一种新的空间分辨率客观评价方法。利用该方法计算超分辨率重建后的遥感图像相比原始遥感图像空间分辨率的提高倍数,从而推断出重建后遥感图像的空间分辨率的大小。在数值测试中,利用不同的超分辨率方法对分级变频矩形光栅图像进行重建,采用提出的空间分辨率评价方法,与归一化均方误差、峰值信噪比、信息熵、灰度平均梯度进行客观评价的结果一致。此方法为遥感图像空间分辨率改进值的计算提供了一种可行的量化模型。  相似文献   

三工河径流系列重建及未来趋势预测   总被引：6，自引：5，他引：1  

黄玉英  商思臣  田万荣 《干旱区地理》2004,27(1):71-74

新疆三工河流域位于天山北麓中段东部 ,发源于博格达峰西北侧 ,著名的高山湖泊、国家级风景区—天池位于该河中游 ,下游是阜康市。对三工河径流量的研究 ,对于保持天池足够的蓄水量及当地环境和资源的开发利用都是非常重要的。但该河仅有短期不连续的径流实测资料 ,且测站断面迁移频繁 ,因而有多种径流估算值。应用Linest函数 ,对影响径流的因子进行筛选 ,重建了三工河 196 1年至 1999年径流系列 ,据此计算三工河多年平均径流量为 0 .6 16× 10 8m3 ,Cv值 0 .10 3。用方差分析法对径流的未来变化趋势作了初步预测 ,为正确评估当地水资源承载能力 ,保持水资源的可持续利用 ,尤其是目前有争议的地下水资源的评估和合理开发提供了定量依据。  相似文献   

北极和南极表面温度对中低纬度海洋热强迫的响应     

刘明嘉  刘福凯  罗义勇 《中国海洋大学学报(自然科学版)》2021,(5)

利用耦合了平板海洋模型的全球气候模式进行了大量的格林函数实验,以探究两极地区对于施加在中低纬度海域的热强迫的气候响应。结果表明,北极地区的气候不仅受到距离较近的北太平洋与北大西洋的影响,远离北极的热带太平洋以及南太平洋也对其气候有显著的影响,南极地区的气候则主要是受到邻近的南大洋的影响。通过经验正交函数法的进一步分析发现,北极响应最显著的区域包括波弗特海(Beaufort Sea)、拉普捷夫海(Laptev Sea)以及北极中心区附近;南极地区的响应主要集中在别林斯高晋海(Bellinsgauzen Sea)区域。另外,利用温度归因法对辐射反馈过程和大气能量输运分解发现,北极地区表面温度的响应主要是受到了反照率反馈以及垂直递减率反馈的影响,而南极地区的响应则主要是反照率反馈发挥了作用。  相似文献   

Redevelopment and the urban forest: A study of tree removal and retention during demolition activities     

《Applied geography (Sevenoaks, England)》2017

Though relationships between urbanization and tree cover are generally well studied, the effect of redevelopment on urban trees, at the scale of the individual property, is not well understood. Developing knowledge in this area is important in order to limit tree loss during redevelopment and thus, ensure sustained ecosystem services. Here, we explore the removal or retention of trees adjacent to building demolition in Christchurch, New Zealand. We mapped the presence or absence of individual trees on 123 properties prior to, and following, building demolition. Using a classification tree (CT) analysis, the presence or absence of 1209 trees was modelled as a function of: tree-related variables, property-related variables, and economic variables. The CT model estimated tree presence/absence with overall accuracy of 80.4%. Results show that 21.6% of all trees were removed as a consequence of building demolition, resulting in a tree canopy cover reduction of 19.7% across all 123 properties. The CT showed that tree crown area was the most important variable for predicting the presence/absence of trees, whereby trees with small crown areas (<7.9 m²) were most frequently removed, especially if they were within 0.7 m of a demolished building. Land value was also an important determinant of tree presence/absence, such that tree removal was more prevalent on properties with higher land value ($/m²). The results provide important new insights into some of the reasons for tree removal or retention during redevelopment at the scale of the individual property where most tree-related decisions are made.  相似文献   

Cultivating climate justice: Green infrastructure and suburban disadvantage in Australia     

《Applied geography (Sevenoaks, England)》2017

Green infrastructure has recently risen to international prominence for its purported capacity to enhance urban sustainability, and particularly to modulate ambient temperatures in the context of climate change. We assess whether residents in a sub-tropical Australian city perceive green infrastructure as an effective climate adaptation response for reducing vulnerability to heat stress. Gold Coast City has pursued urban densification policies, such as reducing block sizes and increasing building heights, to accommodate rapid population growth. Little attention has been given to the combined impact of local heat island effects and global climate change upon lower-income residents in the city's suburban fringe, including rising energy costs associated with cooling homes. The study has three aims: to assess whether social disadvantage is associated with (1) concern about climate change impacts; (2) perceptions about the potential of green infrastructure to offer potential climate-adaptive benefits; and (3) the desire for more urban greening in a working class suburb. We used a mail-back survey to elicit information related to cooling dwellings, awareness of, and concern about, climate change impacts, perceptions of the benefits of green infrastructure, and desire for more urban greening. Results indicate that despite their vulnerability to heat stress, comparatively disadvantaged residents are no more concerned about climate change; nor are they any more inclined to encourage local government to enhance neighbourhood greenery. These residents are, if anything, less likely to perceive benefits of urban greening. Our findings indicate that cultivating support for green infrastructure in disadvantaged neighbourhoods will require parallel efforts to redress inequality.  相似文献   

安塞县退耕还林工程与农业生态经济社会系统协同效应的分析——基于VAR模型的实证分析     

李玥  王继军  胡小宁  赵晓翠 《资源与生态学报(英文版)》2021,12(2):292-301

针对黄土丘陵区退耕还林工程与农业生态经济社会系统协同性研究滞后的现实,运用向量自回归模型(VAR),通过对安塞县1995–2014年相关数据的分析,明确了其协同效应。退耕还林工程结果表明:退耕还林工程对农业生态经济社会系统产生作用的同时,农业生态经济社会系统的改变也反作用于退耕还林工程,明确了退耕还林工程与农业生态经济社会系统之间存在协同互馈的效应。在这一协同过程中,退耕还林工程对农业生态系统的贡献率达34%,明显高于退耕对农业经济系统、农业社会系统的贡献率;农业经济系统对退耕还林工程的影响程度最为明显,贡献率最高点达55.3%且常年稳定,这些都与现实状况相一致。基于此,为了推进退耕还林工程与农业生态经济社会系统的优化耦合,需要在增强生态功能基础上,通过发展碳汇产业促使生态功能的经济显化,构建以提高区域内资源的有效利用率为核心的农业产业–资源链。  相似文献