地形在高大金字塔沙山形成发育过程中的作用——以敦煌鸣沙山-月牙泉地区为例  

The Role of Topographic Barriers in Pyramidal Mega-dune Development:a case study in Mingsha Mountain,Dunhuang,China

作　　者：张伟民[1] 谭立海[1] 边凯[1] 牛清河[1] 

机构地区：[1]中国科学院寒区旱区环境与工程研究所敦煌戈壁荒漠生态与环境研究站,甘肃兰州730000

出　　处：《中国沙漠》2016年第5期1207-1215,共9页Journal of Desert Research

基　　金：国家自然科学基金项目(41271023);国家科技支撑计划项目(20013BAK01B01)

摘　　要：地形在金字塔沙山形成发育过程中起着重要的作用。金字塔沙山通常形成于山前地带,应属于地形屏障影响下形成的一种沙丘类型。首先,上升气流的发育是山前风阻区气流的主要特征,地形屏障是上升气流发生发展的主要原因。沙山的坡脚、坡中及坡顶分别是上升气流的启动区、发育区及衰退区。上升气流是沙山增高增大发育的主要机制。其次,金字塔沙山多发育于局地环流发育较强的地带,局地环流与区域风况配置是形成复杂沙丘类型的重要因素。本区局地环流偏南风不仅持续时间长,且受到鸣沙山微地形的影响,下坡气流较强。实地观测结果破解了常规气候台观测数据难以揭示上升气流及局地环流对金字塔沙丘形成发育的影响。第三,下附地形在沙山形成发育过程中决定着沙丘发育的"临界尺度",即丘体达到"临界尺度"的时候,坡面上升气流及风速放大作用逐渐显现,促使丘体增高增大发育,随着沙丘形态与上升气流的互馈作用进一步增强,金字塔沙丘逐渐形成演化为高大沙山。实地观测进一步证实了金字塔沙山是纵向(横向)沙丘形变的一种形式。并提出了金字塔沙山在地形条件下形成演化的一种新模式。Topographic barriers play an important role in the development process of pyramidal mega-dunes.Pyramid mega-dunes usually develop in front of mountains,and they belong to dunes controlled by topography.Firstly,vertical airflow is a main characteristic of airflow in mountain front wind shadow area.The lower,middle,and top locations of the east-oriented side corresponded to the vertical airflow initiation,development,and recession zones,respectively.Vertical airflow is the main driving mechanism of the upward growth of mega-dunes.Secondly,pyramidal dunes usually develop in areas with strong local air circulation.Local air circulation and regional wind regime consist of three wind directions which contribute to the maintenance and development of complex dunes（pyramidal dunes）.The local air circulation-southerly wind in the study area has high frequency and long duration,and the downhill flow is strong.Thirdly,microreliefs,such as unaka soils and bench terraces,are similar to a ＂rock core＂,serving as the function of ＂ minimum survival size＂.When the dune body reaches the so-called ＂ minimum survival size＂,the vertical airflow begins to develop,making pyramidal dunes to develop to a certain height with a large volume and the end result is a pyramidal mega-dune.Our results also indicate that pyramidal mega-dunes develop from liner dunes controlled by topography.

关 键 词：金字塔沙山 地形屏障 上升气流 局地环流 鸣沙山 

分 类 号：P931.3[天文地球—自然地理学]