新月形沙丘与线形沙丘共生现象探讨——以撒哈拉沙漠为例

Discussion on the symbiosis of barchan dune and linear dune:a case study from Sahara Desert

沙丘共生问题是风沙地貌研究的热点,目前尚缺乏较为深入的探讨。以共生沙丘分布最为广泛的撒哈拉沙漠为例,基于Google Earth高清卫星影像对新月形沙丘和简单线形沙丘共生区域进行参数识别,并对其区域风况特征和形成发育环境进行分析,以探讨共生沙丘形成的可能原因。结果表明:撒哈拉沙漠共有17处典型的共生沙丘区域,是世界上最大的共生沙丘分布区。区域及单个共生沙丘形态参数之间均存在一定相关性,但并不具有理论上应具有的良好相关性,表明影响沙丘共生的因素较为复杂。共生沙丘在低、中、高风能环境以及不同风向变率下均可发育,但主要在低风能环境、中等风向变率\,锐双峰风况下形成。单一的起沙风风向是共生沙丘形成的重要条件,合成输沙势方向与沙丘走向基本一致。除风况外,障碍物如山脉、河流等因素同样对沙丘共生发挥了重要作用。

The phenomenon of symbiotic dunes is a hotspot in the aeolian geomorphology field.Nevertheless,there is still lack of further study.In this paper,based on Google Earth satellite imagery,the wind regime and the development environment of the symbiotic area of barchan dunes and linear dunes in Sahara Desert was deeply discussed to explore the possible reasons for the formation of symbiotic dunes.The results showed that there are 17 symbiotic dune areas in Sahara Desert,which is the largest distribution area of symbiotic dunes in the world.Although morphological parameters have a certain correlation both in regional and individual dune,it does not express as well as in theory,which indicating that the factors affecting symbiotic dunes are complex.In low,medium and high wind energy environment and all wind direction variability can develop symbiotic dunes,but they are mainly formed in low wind energy environment,medium wind direction variability and bimodal wind with an acute angle.Single direction of threshold wind is a significant condition for the formation of symbiotic dunes.The direction of drift potential is basically the same as that of the sand dune.Additionally,wind conditions,obstacles such as mountains,coasts and other factors also play an important role in the formation of symbiotic dunes.In the future,the field survey and numerical simulation should be combined to further interpretation the formation of symbiotic dunes.This will improve our understanding in the formation mechanism of symbiotic dunes,and enrich the formation and evolution theory of aeolian landform.