摘要:

AbstractA series of eskers and esker systems in front of the Casement Glacier, Alaska, were examined in the field in 1962. The same eskers were mapped by photogrammetric methods from aerial photography taken in 1948 and 1963. Comparisons between the 1948 and 1963 maps of the eskers indicate that some of the eskers originated as the deposits of englacial or supraglacial streams and were subsequently let down on to the subglacial floor.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879733

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor

摘要:

AbstractA number of methods for determining the climatic snowline are briefly described. The firn line on glaciers will normally lie slightly lower than the climatic snowline; however, most previous methods for its determination are connected with observations on glaciers. From a study of thedistributionof glaciers and the altitudes of surrounding mountain summits, it is possible to determine a critical height (the“glaciation limit”) which has normally to be exceeded if glaciers should form. This height is approximately 100 metres above the climatic snowline.The glaciation limit was determined on a large number of topographic maps, the results plotted on a small-scale map, and contour lines were drawn showing its regional variation in southern British Columbia and Alberta. The source material and possible errors in the determinations are discussed. A comparison is made with different maps showing precipitation, continentality, land surface elevation, and the 1961 firn line altitude on glaciers. It is concluded that the height of the glaciation limit is inversely connected with the precipitation distribution.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879734

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor

摘要:

AbstractPotential evapotranspirationPEis calculated for Nigeria by a simple energy balance method and compared with the methods of Thornthwaite, Gamier and Penman. Solar radiation is obtained from twelve monthly linear regressions using measurements of sunshine n and radiation at Benin and Kano (Nigeria), Accra(Ghana), Fort Lamy (Tchad) and Niamey (Niger) and values of extraterrestrial radiationSoand possible sunshineNobtained from tables. Daytime net radiation is calculated from a linear regression upon solar radiation which is shown to be appropriate for various stations throughout the world. It is assumed that in thePEmodel nearly all of the net radiation is used to provide the energy for evaporation and the water equivalent of the net radiation (potential water lossER) can be equated withPE.The equation isER=PE=.017 {.617So(a+bn/N)–24} whereaandbare the appropriate monthly intercept and coefficient in a linear regression between solar radiation and sunshine. Measurements ofPEand pan evaporation during the wet season, when‘oasis’effects are small and net radiation is the most important source of energy for evaporation, are in good agreement withER. ERis a better approximation of the measurements than those obtained from the Thornthwaite, Gamier and Penman formulas. The difference between rainfallpandPEdefines areas of dry season deficit and wet season surplus. The indexP-PEis used to delimit the broad vegetation zones which have been mapped by Keay. For the forest-savanna boundaryP-PE=O.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879735

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879736

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor