摘要:

AbstractA special case of the phenomenon of hilltop depressions is examined in southwestern Uganda. The depressions occur on crests of dissected upland formed of steeply inclined quartzites, phyllites, sandstones and shales. The climate of the area is relatively dry for an equatorial region. Out of ca. 300 observed depressions, about a hundred were closely examined. The dimensions of the sample depressions are: 50–350 m in their longer diameter; 1–10 m in depth. Most of them are oval or bowl-shaped. Their siting is controlled by slope (<7°) and structure (strike of the bedding). These controls imply the effect of runoff/percolation ratio and of preference-belts of weatherability and solution. The phenomenon is regarded as continuous throughout the evolution of the relevant surfaces with a possible preference for marginal, dissected areas.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879910

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractGlobal solar radiation measurements and estimates of other radiation fluxes are made for a period of four years on a monthly basis, and one year on a daily basis, for an alpine valley. The site is at 43°02′S, 171°46′E, at an elevation of 780 m a.m.s.l. High day to day variabilities in global solar, net solar, net terrestial and net radiation are observed. A range of albedo values from 13% to 18% is found for tussock grass cover. A regression equation between global solar and net radiation is used and discussed. Mean monthly net radiation during the study year ranged from 269 ly day-1, in November, to 9 ly day-1, in June. The composite nature of net radiation is illustrated and attention is drawn to relatively large size of net terrestial radiation.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879911

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractThe origin, development, and dynamics of nonsorted circles, a variety of patterned ground produced by seasonal frost heaving, are described and analyzed for an alpine location in the Colorado Front Range. Age relations of nonsorted circles and allied features are also discussed.Nonsorted circles favour exposed snow-free locations, particularly the frontal areas of turf-banked lobe and terrace treads. Here, wind scour causes the disruption and removal of the protective mat of the alpine turf. Frost penetration into freshly exposed sites promotes, in the presence of adequate moisture, differential frost heaving with the subsequent doming of circle centres.A buried A horizon observed in a number of pits dug into nonsorted circles occupying a turf-banked lobe, was dated at 10,400±400 radiocarbon years. The material in which the circles subsequently developed became sufficiently stable for soil development by the close of the Pinedale Glaciation (7,500 B.P.). Field evidence suggests they may be a recent phenomena, initiated after the close of the Gannett Peak stade of Neoglaciation.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879912

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractAll aspects of surface form can be considered to reflect surface roughness. Horizontal variation includes the concepts of texture and grain, while vertical variation is discussed under relief. The relationships between these are embodied in slope and the dispersion of slope magnitude and orientation. The distribution of mass within the elevation range of a topographic surface is described under hypsometry. Parameters for further investigation are selected from these categories after an examination of the relationships among the variables using correlation analysis.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879913

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractTopographic information can be digitized in several ways. Sampling may be surface-random or surface-specific. Surface-random sampling includes grids, contours, and randomly-located points. In this study, grids and surface-specific sampling are compared with reference to the problem of estimating certain geomorphometric parameters.Results of empirical comparison of the methods over six selected topographic samples are presented. The assumption of a linear relationship between grid spacing and grid error is used to estimate the grid spacing which would be required to produce the same average errors as the surface-specific point samples. For the three parameters used, these hypothetical grids require more digitization time and computer storage space than the surface-specific point data sets.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879914

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractClimbing ripple cross-laminae were used to obtain two-dimensional palaeocurrent data from glaciofluvial and glaciolacustrine sands. These data were then compared to the Gaussian, von Mises and circular uniform frequency distributions for goodness-of-fit atα= 0.05 andα= 0.01. Individual sample distributions taken from sampling units of one cubic metre were best described by the Gaussian and von Mises distributions. Atα= 0.05, only the Gaussian provided an adequate fit for samples with relatively small standard deviations (∼14°to 18°). For samples with larger standard deviations (∼20°to 40°) both the Gaussian and von Mises distributions were satisfactory fits atα= 0.01, but atα= 0.05 the Gaussian was the better fit for most of the samples. None of the three theoretical distributions adequately described the sampling distribution, which had a standard deviation of 50°. The best fit distribution for samples with standard deviations around 50°is probably transitional between a von Mises and a circular uniform distribution at bothα= 0.05 and 0.01.In future studies of similar deposits, if the same size of sampling unit (1 cubic metre) is used and if the same average flow variability is assumed, a minimum of about 25 observations will be necessary in each sample in order to estimate the sample vector resultant to within±10°of the true average flow direction atα= 0.05; and atα= 0.01, at least 45 observations will be necessary.Analysis-of-variance of the data in their vectorial form gaveω= 4.273 andβ= 0.5399 for the within and between-site estimates of the population variance. The concentration parameter,χ, was 6.998 for the grand vector resultant and gaveψ≃56°for the semi-angle of confidence,ψ, around the grand resultant. Several combinations of sample size and number were calculated (a) to achieve the same value forχin estimating the grand vector resultant in separate investigations, and (b) to increase the valueχ.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879915

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractDuring spring 1973, snowmelt and melt-water discharge in a small alpine basin in the Coast Mountains of British Columbia were investigated. The snow was completely ripened at this period but thickness of the pack affected the movement and storage of meltwater to the extent that the lag times and recession flows of a snow-fed stream became noticeably different. Snow cover in the basin was also variable during the study period and the spatial variations in streamflow give consistent indication of variable alpine snowmelt source areas.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879916

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractThe main components of the land surface in a small area of the Southern Alps of New Zealand have been produced during the glacial-periglacial episodes of the Late Pleistocene. In ice free areas, morphogenesis was associated with congelifraction and the production of scree. Where scree accumulated, slopes evolved towards a smooth, regular form, only slightly concave, characterized by a scree-veneered upper slope passing downslope to a talus zone. On some valley sides, a colluvial foot slope was formed at the base of the talus. It probably resulted from slope wash. Where valley glaciers were present Richter's denudation slope formed alongside the ice. In most cases such slopes were rejuvenated during subsequent stadials, as the result of a retrogressive glacial history, and have been dissected by chutes and funnels to provide the scree now mantling old glacial walls. Fluvial processes were active at least during the waning phases of the cold-climate periods and built alluvial fans at the margins of the glacial troughs. It is believed that similar morphogenesis occurred during the glacial-periglacial phases of the Late Pleistocene in a large area east of the Main Divide in the Southern Alps.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879917

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractThe presence of glacial marine drift, a hybrid deposit containing sub-fossil shells of age about 12,000 years B.P. in the lowland of Western Iceland, together with a system of presumed lateral melt-water channels with associated deposits, over and around the rim of the bounding ridge and valley terrain, suggests that piedmont ice in the lowland, resulting from coalescence of ice streams from the higher ground inland, floated as an ice shelf as the ice thinned and sea-level rose. The deposits in the area may be the result of fluvial transport in englacial and subglacial conduits, with subsequent deposition on dry land or in water of varying depths. Till is found in varying, but ususally small, proportions in the glacial marine drift but is otherwise absent except in the extreme north-east of the area.

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879918

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractClimatological data from a scientific field study conducted in the Sakaerat Forest, Thailand, from November, 1967 to September, 1970 are summarized and presented. The forest area is comprised of dry evergreen and dry dipterocarp forest with cleared areas in various stages of regeneration. The forest canopy ranges from 20–35 m in height with a lower story ranging from 5–17 m in height.Diurnal and/or seasonal variations of temperature, humidity, precipitation, evaporation, moisture advection and hours of sunshine are analyzed to identify the climatological make-up of the forest area in the context of the moist southwest and dry northeast monsoonal cycles dominating Southeast Asia. Data from eleven other locations in Southeast Asia are pooled with the data from Sakaerat Forest to obtain a coherent picture of the complex monsoon system in this area of the world.(Publication Nr. 105 of the Graduate Program in Meteorology).

ISSN:0435-3676    

DOI:10.1080/04353676.1975.11879919

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor