排序方式： 共有5条查询结果，搜索用时 15 毫秒
1
1.
Robert Andrle 《自然地理学》2013,34(3):270-281
The traditional measure of river-channel sinuosity, P, is shown to vary with scale of measurement, the geometric character of the particular reach, and the starting point of the divider walk. Meander wavelength, L, suffers from non-reproducibility caused by the subjective identification of inflection points, a problem compounded by the irregularity of river meanders. Applicability of the angle measure technique (AMT) to the measurement of meander planform is demonstrated. The AMT considers variations in the complexity of meandering with scale, eliminating the dependence of results on scale of measurement. The AMT also samples the river at random points rather than sequentially, unlike the divider walk used to calculate P, avoiding the dependence of P on the starting position of the divider walk. The AMT also does not require subjective identification of inflection points as wavelength L does. Additionally, the traditional measures P and L are difficult to apply to manifestly underfit rivers. In this study, the AMT is applied to two underfit rivers and measures of meander size and sinuosity are calculated for each set of meanders. [Key words: sinuosity, meanders, wavelength, underfit river, fluvial geomorphology.] 相似文献
2.
Through a series of simulation experiments in the laboratory on the broad‐leaved tree Acer mono Maxim, we obtain interception datasets of individual events under different rainfall intensities and leaf area indexes (LAIs). Based on the data, the relationship between rainfall intensity and maximum interception of per unit LAI is quantified. The variation of interception with canopy wetness index is also identified. Hence, an interception model, in which interception is calculated using rainfall intensity and LAI, is constructed with consideration of canopy wetness. Finally, according to the validation experiments, it is concluded that the precision of the model is 92·7%. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
云南省是研究我国植物多样性,植物区系演化及被子植物迁徙路线的有利场所。文中鉴定并描述了采自云南临沧上中新统邦卖组的槭属(Acer)8块叶片和17块翅果化石,共鉴定为4个种,其中包括1个新种和1个相似种,分别为Acer lincangense sp.nov.和Acer cf.jingdongense。槭属化石在云南邦卖组的出现,证明了该植物群具有北温带和古热带的混生特征,反映了当时植物区系类型的多样化构成了云南现代植物多样性的基础。另外,通过对Acer全球大化石记录以及现生种的统计,总结得出槭属的地史演化具有3个发展高峰期:依次为始新世、中新世和全新世,从古至今呈现一种螺旋式递增趋势。 相似文献
4.
Richard A. Marston Larry O. Pochop Greg L. Kerr Marjorie L. Varuska David J. Veryzer 《自然地理学》2013,34(2):115-123
Parallax measurements on matching aerial photograph stereopairs from 1958 and 1983 were used to calculate the ice lost from Dinwoody Glacier in the Wind River Range of Wyoming. The ice remaining in Dinwoody Glacier was measured using a portable radio echo-sounder. Isopach maps of lost ice thickness and remaining ice thickness in the glacier were constructed from these point measurements. Calculations of lost and remaining ice volumes, converted to water-equivalent values, were derived from planimetric measurements from these isopach maps. The water equivalent remaining in Dinwoody Glacier is approximately equal to that lost between 1958 and 1983. Should this rate of downwasting and retreat continue, Dinwoody Glacier will disappear in 27 years, with significant adverse impacts on late summer and early fall water supplies for downstream irrigators and instream flow needs. [Key words: glaciers, glacier runoff, radio echo-sounding, Wind River Range, Wyoming.] 相似文献
5.
1