| 释义 |
▪ I. seif Physical Geogr.|siːf, seɪf|
Also sif.
[ad. Arab. saif, lit. ‘sword’.]
A sand dune having the form of a narrow ridge elongated in a direction parallel to that of the prevailing wind. Also seif dune.
1925W. J. H. King Myst. Libyan Desert xxiii. 221 In front of us..was a high three-headed sif, or longitudinal sand dune. 1931Geogr. Jrnl. LXXVIII. 16 In form it is a typical sif dune, a long straight ridge of sand with a single longitudinal chain of crests rising to billowy pyramids set at regular intervals, in silhouette something like huge saw-teeth. 1933Ibid. LXXXII. 107 The Prince's map of this area shows a sudden change in the direction of the straight parallel lines of seif dunes which cross the country. 1941R. A. Bagnold Physics of Blown Sand & Desert Dunes xv. 234 The early observers..held that it blew at right angles to the dune direction, whereas later observations over a longer period show that it blows parallel to the dunes... Both are right, since cross-winds are essential for seif formation. 1953Sci. News XXVII. 16 The greatest height recorded for a seif dune is 210 metres... Their lengths vary from about 60 to 120 kilometres. 1975Nature 20 Feb. 617/2 Until the recent drought, seif dunes were mainly active in this region north of the 150-mm isohyet. 1976Ibid. 26 Feb. 654/1 Nearby, near the oasis of Bilma, a small dune field of seifs and barchans again indicates that the wind at right angles to the barchans would be to the left of the main trend.
▪ II. seif
see sief Obs. |