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1.
Based on cross-dating tree rings from the Tianmu Mountain, Zhejiang Province, the tree rings α-cellulose δ 13C time series was measured. By spectrum analysis, the variation of tree-ring δ13C sequence shows a quasi periodicity of 4.4 years, which is coincident with the standard cycle of El Nino. After removing the long-term decrease trend of the δ13C variation related to atmospheric CO2 concentration, the response of the δ13C to climate elements was analyzed using meteorology data from a nearby weather station. The results suggest that there is a distinct relativity between high-frequency variation of tree ring δ 13C series and seasonal climate parameters, e.g. Temperature and precipitation, with a significant time-lag effect. In addition, the high frequency also reflects the strength change of the East Asian Monsoon. The multiple regression method was employed to reconstruct the historical climate, and to analyze the climate change and trend in the last 160 years in the northern Zhejiang Province. 相似文献
2.
DavidL.B.Jupp 《遥感学报》1997,(Z1)
森林和林地的图象二向性反射函数是一个统计函数,较之小尺度的树冠,它更多地用于大尺度的均匀覆盖的地块。用航空象片和高空间分辨率扫描仪数据作的图象热点影响研究在小尺度下显示出很大方差,而且,太阳和观测角度的交互变化进一步增加了这种反射各向异性变化的方差并有规律地继续呈现在分辨率低的图象中,这被称作BRVF或二向性反射方差函数。近年来,作为一种解释结构的手段,高分辨率图象的方向性方差和直方图结构越来越受到重视,这方面的数据也越来越多。这项工作是利用图象方差来解释结构问题(Strahler和李小文倡导)的一种延伸,并在过去15年中由众多人员作了大量工作。在树冠尺度下,森林的直方图和二向反射方差函数可以计算出来,这里利用了近似迭代函数来处理这些数据并和数值积分模拟进行了对比,结果显示可对二向性反射方差函数的测量和引入直方图的各向异性进行准确建模。 相似文献
3.
多角度成象对于获取多角度遥感数据是非常重要的。在对多角度数据进行分析之前,首先要对多角度图象进行配准。经过配准,可以识别出相同的地面目标。在配准过程中,一个主要的困难是由于观察角度的不同、双向反射变化及大气的影响造成的图象灰度变化。如何解决灰度变化的影响关系到图象的配准精度。我们在该文中介绍一种多角度图象配准过程,包括预处理、基于层次结构的图象灰度相关配准。为了去掉大角度造成的灰度变化,我们用改进的模板匹配进行配准。这种方法的优点是与配准模板灰度均值无关,只与灰度变化程度有关。配准过程中也同时考虑到纹理的变化。整个配准过程是沿着观测角度增大的方向进行的序列图象配准,以提高大角度图象配准精度。最后,图象的纠正采用局部自适应几何纠正以获得较满意的结果。我们用法国CNES提供的POLDER飞机模拟多角度图象进行配准,并提取了小麦和水稻等植被的多角度信息。 相似文献
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5.
从像质的概念出发,导出了像质评定的简单公式。在干涉图的每个选定点上测量条纹间的间隔和角度来计算几何光线的斜率误差,然后把这些角度误差画在一张图纸上用以表示几何点扩散函数的角度大小,可以方便而简洁地评定成像质量,避免了复杂的计算。 相似文献
6.
Reconstruction of paleocoastlines for the northwestern South China Sea since the Last Glacial Maximum 总被引:1,自引:0,他引:1
The range of relative sea level rise in the northwestern South China Sea since the Last Glacial Maximum was over 100 m. As
a result, lowland regions including the Northeast Vietnam coast, Beibu Gulf, and South China coast experienced an evolution
from land to sea. Based on the principle of reconstructing paleogeography and using recent digital elevation model, relative
sea level curves, and sediment accumulation data, this paper presents a series of paleogeographic scenarios back to 20 cal.
ka BP for the northwestern South China Sea. The scenarios demonstrate the entire process of coastline changes for the area
of interest. During the late glacial period from 20 to 15 cal. ka BP, coastline slowly retreated, causing a land loss of only
1×104 km2, and thus the land-sea distribution remained nearly unchanged. Later in 15–10 cal. ka BP coastline rapidly retreated and
area of land loss was up to 24×104km2, causing lowlands around Northeast Vietnam and South China soon to be underwater. Coastline retreat continued quite rapidly
during the early Holocene. From 10 to 6 cal. ka BP land area had decreased by 9×104km2, and during that process the Qiongzhou Strait completely opened up. Since the mid Holocene, main controls on coastline change
are from vertical crustal movements and sedimentation. Transgression was surpassed by regression, resulting in a land accretion
of about 10×104km2.
Supported by Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (Grant No. MSGL0711), the Guangdong Natural
Science Foundation (Grant No. 04001309) and Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy
of Sciences (Grant No. MGE2007KG04) 相似文献
7.
The relationships between two-dimensional image analysis of soil thin-sections and tracer breakthrough curves has been studied for a silty clay loam brown earth soil under saturated conditions. Initial tracer breakthrough is well in advance of one pore volume. Discrepancies between Quantimet image analysis and breakthrough curve characterization were related by inference to the role of infrequently occurring macropores not necessarily sampled on the two-dimensional images. A fundamental difficulty found in the use of image analysis is the uncertain nature of the relationship between the two-dimensional image and the three-dimensional pore system. Caution is needed in using Quantimet image analysis to describe gross properties of the three-dimensional pore system. 相似文献
8.
Quantifying preferential flow in soils: A review of different techniques 总被引:19,自引:0,他引:19
Preferential flow (PF) in soil has both environmental and human health implications since it favours contaminant transport to groundwater without interaction with the chemically and biologically reactive upper layer of soil. PF is, however, difficult to measure and quantify. This paper reviews laboratory and field techniques, such as breakthrough curves, dye tracing, and scanning techniques, for evaluating PF in soil at different scales. Advanced technologies, such as scanning techniques, have increased our capability to quantify transport processes within the soil with minimal soil disturbance. Important issues with respect to quantifying PF concern large-scale studies, frozen soil conditions, tracing techniques for particles and gases, a lack of simple mathematical tools for interpreting field data, and the lack of a systematic approach for comparing PF data resulting from different measurement techniques. Also, more research is required to quantify the relative importance of the various PF processes that occur in soil rather than the integrated result of all PF processes in soils. 相似文献
9.
10.