EFFECTS OF ATMOSPHERIC CONDITIONS ON WIND PROFILES AND AEOLIAN SAND TRANSPORT WITH AN EXAMPLE FROM WHITE-SANDS-NATIONAL-MONUMENT

被引:34
作者
FRANK, A
KOCUREK, G
机构
[1] Department of Geological Sciences, University of Texas, Austin, Texas
关键词
WIND; VELOCITY PROFILE; ATMOSPHERE; WHITE SANDS;
D O I
10.1002/esp.3290190806
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
Quantifying aeolian sand transport rates relies upon the computation of the near-surface shear velocity (u*) determined from velocity profiles of the wind. While it has been recognized that various conditions, such as saltation, surface roughness, surface slope and atmospheric conditions, have an effect on the velocity profile, it is commonly assumed that measurements made above the surface will be representative of the near-surface shear velocity. Airflow and temperature data collected over a flat substrate at White Sands National Monument in New Mexico, however, show the significant effects that;atmospheric conditions have on velocity profiles. During the day, when solar insolation is heating the surface, atmospheric conditions in the lowest several metres become unstable, resulting in enhanced convection and vertical mixing so that the velocity gradient changes little with height. As a result, the shear stress in this region of vertical mixing lessens, while the near-surface shear stress is increased because the higher wind speeds are now nearer the surface. At night, the near-surface atmospheric conditions are stable, thereby reducing convection and vertical mixing, resulting in stratified airflow and increased shear velocity away from the surface. Unless this atmospheric effect is accounted for, estimates of sediment transport rates may be in error by as much as a factor of 15 times when wind speeds are near threshold velocity. At wind speeds approaching 10 m s(-1), at 5m above the surface, this error in computing sediment transport is reduced to a factor of only two to three times, and may be within the range of measurement error.
引用
收藏
页码:735 / 745
页数:11
相关论文
共 17 条
[1]  
BAGNOLD RA, 1941, PHYSICS BLOWN SAND D
[2]  
Burkinshaw JR, 1993, GEOLOGICAL SOC SPECI, V72, P25
[3]  
DYER AJ, 1981, BOUND-LAY METEOROL, V22, P3
[4]  
FRANK AJ, 1994, UNPUB EARTH SURFACE
[5]  
GREELEY R, 1991, NASA4378 CONTR REP
[6]   TURBULENT WIND FLOW OVER A LOW HILL [J].
JACKSON, PS ;
HUNT, JCR .
QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, 1975, 101 (430) :929-955
[7]   VARIATIONS IN WIND VELOCITY AND SAND TRANSPORT ON THE WINDWARD FLANKS OF DESERT SAND DUNES [J].
LANCASTER, N .
SEDIMENTOLOGY, 1985, 32 (04) :581-593
[8]  
Lancaster N, 1991, ACTA MECHANICA S, V2, P89
[9]   VELOCITY PROFILES MEASURED ON THE WINDWARD SLOPE OF A TRANSVERSE DUNE [J].
MULLIGAN, KR .
EARTH SURFACE PROCESSES AND LANDFORMS, 1988, 13 (07) :573-582
[10]   SALTATION OF UNIFORM GRAINS IN AIR [J].
OWEN, PR .
JOURNAL OF FLUID MECHANICS, 1964, 20 (02) :225-242