新月形沙丘对湖积平原风蚀荒漠化的影响
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摘要
新月形沙丘是风蚀荒漠化过程中伴随的重要风积地貌类型,在以往的研究中主要侧重于沙丘体表面动力学过程,而关于沙丘在风蚀荒漠化过程中的作用鲜有报道。本文在台特玛湖的干涸湖盆区(曾经的塔里木河尾闾湖),采用测钎法,实地测定了新月形沙丘周围地表的蚀积变化,同时采用室内风洞模拟了典型新月形沙丘地表的气流分布模式,系统分析了新月形沙丘对地表蚀积影响的作用机理。结果表明:在新月形沙丘影响下,沙丘周围地表风蚀强度不均一,在沙丘迎风坡前区和沙丘左右翼,风蚀深度略大于不受沙丘影响区(CK),但单位面积平均净蚀积量接近平衡状态;在沙丘背风坡前区以风积为主,而在背风侧尾流区,地表以风蚀为主,且随着沙丘体积增加,单位面积平均净风蚀量也略有增大。在内陆干旱区干涸湖盆风蚀荒漠化过程中,新月形沙丘通过改变地表流场结构,使风沙流饱和度发生空间分异,从而影响了下伏地表蚀积的空间分布,尤其加剧了背风侧尾流区的风蚀,使新的风蚀面裸露,破坏沉积层结构,促进了河湖相沉积平原风蚀荒漠化的发展。
Barchan dune is an important type of aeolian landform and forms during the process of desertification.In the previous researches,more researchers focused mainly on the surface dynamic process of barchan dune but less on the influence of barchan dune on surface wind erosion during desertification process. In this paper,the plugging-brazing method was used to measure the distribution pattern of wind erosion/deposition on the surface around barchan dunes at the Taitema playa. The wind tunnel was used to simulate the distribution pattern of airflow over the typical barchan dune. The mechanism of barchan dune affecting surface wind erosion around dune was analyzed. The results showed that the airflow structure changed with the varying geometry shapes of barchan dunes,and it affected significantly the intensity of wind erosion/deposition over the surface. Although the wind erosion depth and sedimentary thickness were slightly greater than those on flat sand,the average volume of net wind erosion per unit area was close to an equilibrium in the frontal region of windward slope and on both sides of dunes.Deposition was dominant in the frontal region on leeward slope of barchan dune,but wind erosion was dominant on the surface of flank wake zone of leeward slope. The average volume of net wind erosion per unit area was slightly increased with the increase of dune size. In a word,the barchan dunes affect the intensity of surface wind erosion and deposition during the process of desertification in playa.
Barchan dune is an important type of aeolian landform and forms during the process of desertification.In the previous researches,more researchers focused mainly on the surface dynamic process of barchan dune but less on the influence of barchan dune on surface wind erosion during desertification process. In this paper,the plugging-brazing method was used to measure the distribution pattern of wind erosion/deposition on the surface around barchan dunes at the Taitema playa. The wind tunnel was used to simulate the distribution pattern of airflow over the typical barchan dune. The mechanism of barchan dune affecting surface wind erosion around dune was analyzed. The results showed that the airflow structure changed with the varying geometry shapes of barchan dunes,and it affected significantly the intensity of wind erosion/deposition over the surface. Although the wind erosion depth and sedimentary thickness were slightly greater than those on flat sand,the average volume of net wind erosion per unit area was close to an equilibrium in the frontal region of windward slope and on both sides of dunes.Deposition was dominant in the frontal region on leeward slope of barchan dune,but wind erosion was dominant on the surface of flank wake zone of leeward slope. The average volume of net wind erosion per unit area was slightly increased with the increase of dune size. In a word,the barchan dunes affect the intensity of surface wind erosion and deposition during the process of desertification in playa.
引文
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[2]杨岩岩,刘连友,屈志强,等.新月形沙丘研究进展[J].地理科学,2014,34(1):76-83.[Yang Yanyan,Liu Lianyou,Qu Zhiqiang,et al. A review of barchan dunes[J]. Scientia Geographica Sinica,2014,34(1):76-83.]
[3]董玉祥,黄德全.海岸新月形沙丘移动与形态变化的典型研究[J].地理科学,2014,34(7):863-869.[Dong Yuxiang,Huang Dequan. Typical research on the movement and topographic change of coastal crescent dune[J]. Scientia Geographica Sinica,2014,34(7):863-869.]
[4]常兆丰,马中华,朱淑娟,等.新月形沙丘顶点与沙脊线重合和分离的两种过程——以甘肃河西走廊沙区为例[J].干旱区研究,2017,34(1):167-173.[Chang Zhaofeng,Ma Zhonghua,Zhu Shujuan,et al. Processes of superposition and separation of barchan dunes on the top and ridge line:A case study in the desert areas of the Hexi Corridor,Gansu province[J]Arid Zone Research,2017,34(1):167-173.]
[5]贾文茹,李生宇,马学喜,等.塔克拉玛干沙漠腹地横向沙丘表面紧实度分异特征[J].干旱区研究,2016,33(3):664-671.[Jia Wenru,Li Shengyu,Ma Xuexi,et al. Spatial variation of compaction on transverse dune surface in hinterland of the Taklimakan Desert[J]. Arid Zone Research,2016,33(3):664-671.]
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[7] Walker I J,Nickling W G. Simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel[J]. Earth Surface Processes&Landforms,2003,28(10):1 111-1 124.
[8] Baddock M C,Livingstone I,Wiggs G F,et al. The geomorphological significance of airflow patterns in transverse dune interdunes[J]. Geomorphology,2007,87(4):322-336.
[9] Smith A B,Jackson D W T,Cooper J A G. Three-dimensional airflow and sediment transport patterns over barchan dunes[J]. Geomorphology,2017,278:28-42.
[10]李恒鹏,李波,陈广庭.新月形沙丘迎风坡气流加速模拟[J].中国沙漠,2001,21(1):24-27.[Li Hengpeng,Li Bo,Chen Guangting. Simulation of flow accelerating on the windward of barchan[J]. Journal of Desert Research,2001,21(1):24-27.]
[11]Wiggs G F S,Weaver C M. Turbulent flow structures and aeolian sediment transport over a barchan sand dune[J]. Geophysical Research Letters,2012,39(5):1-7.
[12]Dong Z,Qian G,Ping L,et al. Turbulence fields in the lee of twodimensional transverse dunes simulated in a wind tunnel[J]. Earth Surface Processes&Landforms,2009,34(2):204-216.
[13]马学喜,李生宇,王海峰,等.流动沙漠地形起伏区尼龙网方格沙障破损程度的空间分异[J].自然灾害学报,2015,24(2):81-88.[Ma Xuexi,Li Shengyu,Wang Haifeng,et al. Spatial differentiation of breakage degree of nylon net checkerboard barrier in sites with rugged terrain in Taklimakan Desert[J]. Journal of Natural Disaster,2015,24(2):81-88.]
[14]李生宇,雷加强,徐新文,等.塔里木沙漠公路影响下的地表形态变化[J].科学通报,2006,51(增刊):81-87.[Li Shengyu,Lei Jiaqiang,Xu Xinwen,et al. Surface morphology changes affected by Tarim Desert highway[J]. Chinese Science Bulletin,2006,51(Suppl. 1):81-87.]
[15]蔡东旭,李生宇,刘耀中,等.台特玛湖干涸湖盆区植物风影沙丘的形态特征[J].干旱区地理,2017,40(5):1 021-1 027.[Cai Dongxu,Li Shengyu,Liu Yaozhong,et al. Morphological characteristics of shadow dunes of plant at dry lakebed of Taitema Lake[J]. Arid Land Geography,2017,40(5):1 021-1 027.]
[16] White B R. Laboratory simulation of aeolian sand transport and physical modeling of flow around dunes[J]. Annals of Arid Zone,1996,35(3):187-213.
[17]Zhang W,Kang J H,Lee S J. Tracking of saltating sand trajectories over a flat surface embedded in an atmospheric boundary layer[J]. Geomorphology,2007,86(3):320-331.
[18]Weaver C M,Wiggs G F S. Field measurements of mean and turbulent airflow over a barchan sand dune[J]. Geomorphology,2011,128(1-2):32-41.
[19]Wiggs G F S,Livingstone I,Warren A. The role of streamline curvature in sand dune dynamics:Evidence from field and wind tunnel measurements[J]. Geomorphology,1996,17(1):29-46.
[20]Wiggs G F S,Bullard J E,Garvey B,et al. Interactions between airflow and valley topography with implications for Aeolian sediment transport[J]. Physical Geography,2002,23(5):366-380.
[21]Gao X,Zhang D,Rozier O,et al. Transport capacity and saturation mechanism in a real-space cellular automaton dune model[J]. Advances in Geosciences,2014,37:47-55.
[22]Livingstone I,Wiggs G F S,Weaver C M. Geomorphology of desert sand dunes:A review of recent progress[J]. Earth Science Reviews,2007,80(3):239-257.
[23]张春来,郝青振,邹学勇,等.新月形沙丘迎风坡形态及沉积物对表面气流的响应[J].中国沙漠,1999,19(4):359-363.[Zhang Chunlai,Hao Qingzhen,Zou Xueyong,et al. Response of morphology and deposits to surface flow on windward slope of barchan dune[J]. Journal of Desert Research,1999,19(4):359-363.]
[24]钱广强,董治宝,罗万银,等.横向沙丘背风侧气流重附风洞模拟[J].中国沙漠,2008,28(1):16-20.[Qian Guangqiang,Dong Zhibao,Luo Wanyin. Wind tunnel simulation on flow reattachment on the lee of transverse dunes[J]. Journal of Desert Research,2008,28(1):16-20.]
[25]Jiang H,Dun H,Tong D,et al. Sand transportation and reverse patterns over leeward face of sand dune[J]. Geomorphology,2017,283:41-47.
[26] Watson A. Variations in wind velocity and sand transport on the windward flanks of desert sand dunes[J]. Sedimentology,2010,32(4):581-593.
[27]哈斯,王贵勇.沙丘背风侧气流的变化特征及其意义[J].地理科学,2000,20(6):573-576.[Ha Si,Wang Guiyong. Variation in dune Lee-side airflow and its significance[J]. Scientia Geographica Sincia,2000,20(6):573-576.]
[28] Nickling W G,Neuman C M,Lancaster N. Grainfall processes in the lee of transverse dunes,Silver Peak,Nevada[J]. Sedimentology,2010,49(1):191-209.
[29] Nelson J M,Mclean S R,Wolfe S R. Mean flow and turbulence fields over two-dimensional bed forms[J]. Water Resources Research,1993,29(12):3 935-3 953.
[30]Durán O,Andreotti B,Claudin P. Numerical simulation of turbulent sediment transport,from bed load to saltation[J]. Physics of Fluids,2012,24(10):709-737.
[31]Sauermann G,Kroy K,Herrmann H J. Continuum saltation model for sand dunes[J]. Physical Review E,2001,64(3):031 305.
[32]Walker I J,Nicklingb W G. Dynamics of secondary airflow and sediment transport over and in the lee of transverse dunes[J]. Progress in Physical Geography,2002,26(1):47-75.
[33]葛拥晓,吉力力·阿不都外力,马龙,等.新疆艾比湖干涸湖底沉积物粒径分布及其对风蚀的响应[J].干旱区研究,2014,31(4):636-642.[Ge Yongxiao,Jilili Abuduwaili,Ma Long,et al.Response of granularity distribution to wind erosion in the Playa of the Ebinur Lake,Xinjiang,Northwest China[J]. Arid Zone Research,2014,31(4):636-642.]
[34]李生宇,谷峰,王海峰,等.塔克拉玛干沙漠河湖相沉积平原风蚀地貌发育的外营力作用机制[J].干旱区地理,2012,35(3):358-364.[Li Shengyu,Gu Feng,Wang Haifeng,et al. Exogenic forces action mechanism in the development process of erosion landform on alluvial plains composed of fluvial-lacustrine deposits in the Taklimakan Desert[J]. Arid Land Geography,2012,35(3):358-364.]
[2]杨岩岩,刘连友,屈志强,等.新月形沙丘研究进展[J].地理科学,2014,34(1):76-83.[Yang Yanyan,Liu Lianyou,Qu Zhiqiang,et al. A review of barchan dunes[J]. Scientia Geographica Sinica,2014,34(1):76-83.]
[3]董玉祥,黄德全.海岸新月形沙丘移动与形态变化的典型研究[J].地理科学,2014,34(7):863-869.[Dong Yuxiang,Huang Dequan. Typical research on the movement and topographic change of coastal crescent dune[J]. Scientia Geographica Sinica,2014,34(7):863-869.]
[4]常兆丰,马中华,朱淑娟,等.新月形沙丘顶点与沙脊线重合和分离的两种过程——以甘肃河西走廊沙区为例[J].干旱区研究,2017,34(1):167-173.[Chang Zhaofeng,Ma Zhonghua,Zhu Shujuan,et al. Processes of superposition and separation of barchan dunes on the top and ridge line:A case study in the desert areas of the Hexi Corridor,Gansu province[J]Arid Zone Research,2017,34(1):167-173.]
[5]贾文茹,李生宇,马学喜,等.塔克拉玛干沙漠腹地横向沙丘表面紧实度分异特征[J].干旱区研究,2016,33(3):664-671.[Jia Wenru,Li Shengyu,Ma Xuexi,et al. Spatial variation of compaction on transverse dune surface in hinterland of the Taklimakan Desert[J]. Arid Zone Research,2016,33(3):664-671.]
[6]闫德仁,姚洪林,胡小龙.流动沙丘不同部位风蚀积沙特征研究[J].水土保持通报,2015,35(4):288-292.[Yan Deren,Yao Honglin,Hu Xiaolong. Characteristics of wind erosion and accumulated sand in different positions of mobile dune[J]. Bulletin of Soil and Water Conservation,2015,35(4):288-292.]
[7] Walker I J,Nickling W G. Simulation and measurement of surface shear stress over isolated and closely spaced transverse dunes in a wind tunnel[J]. Earth Surface Processes&Landforms,2003,28(10):1 111-1 124.
[8] Baddock M C,Livingstone I,Wiggs G F,et al. The geomorphological significance of airflow patterns in transverse dune interdunes[J]. Geomorphology,2007,87(4):322-336.
[9] Smith A B,Jackson D W T,Cooper J A G. Three-dimensional airflow and sediment transport patterns over barchan dunes[J]. Geomorphology,2017,278:28-42.
[10]李恒鹏,李波,陈广庭.新月形沙丘迎风坡气流加速模拟[J].中国沙漠,2001,21(1):24-27.[Li Hengpeng,Li Bo,Chen Guangting. Simulation of flow accelerating on the windward of barchan[J]. Journal of Desert Research,2001,21(1):24-27.]
[11]Wiggs G F S,Weaver C M. Turbulent flow structures and aeolian sediment transport over a barchan sand dune[J]. Geophysical Research Letters,2012,39(5):1-7.
[12]Dong Z,Qian G,Ping L,et al. Turbulence fields in the lee of twodimensional transverse dunes simulated in a wind tunnel[J]. Earth Surface Processes&Landforms,2009,34(2):204-216.
[13]马学喜,李生宇,王海峰,等.流动沙漠地形起伏区尼龙网方格沙障破损程度的空间分异[J].自然灾害学报,2015,24(2):81-88.[Ma Xuexi,Li Shengyu,Wang Haifeng,et al. Spatial differentiation of breakage degree of nylon net checkerboard barrier in sites with rugged terrain in Taklimakan Desert[J]. Journal of Natural Disaster,2015,24(2):81-88.]
[14]李生宇,雷加强,徐新文,等.塔里木沙漠公路影响下的地表形态变化[J].科学通报,2006,51(增刊):81-87.[Li Shengyu,Lei Jiaqiang,Xu Xinwen,et al. Surface morphology changes affected by Tarim Desert highway[J]. Chinese Science Bulletin,2006,51(Suppl. 1):81-87.]
[15]蔡东旭,李生宇,刘耀中,等.台特玛湖干涸湖盆区植物风影沙丘的形态特征[J].干旱区地理,2017,40(5):1 021-1 027.[Cai Dongxu,Li Shengyu,Liu Yaozhong,et al. Morphological characteristics of shadow dunes of plant at dry lakebed of Taitema Lake[J]. Arid Land Geography,2017,40(5):1 021-1 027.]
[16] White B R. Laboratory simulation of aeolian sand transport and physical modeling of flow around dunes[J]. Annals of Arid Zone,1996,35(3):187-213.
[17]Zhang W,Kang J H,Lee S J. Tracking of saltating sand trajectories over a flat surface embedded in an atmospheric boundary layer[J]. Geomorphology,2007,86(3):320-331.
[18]Weaver C M,Wiggs G F S. Field measurements of mean and turbulent airflow over a barchan sand dune[J]. Geomorphology,2011,128(1-2):32-41.
[19]Wiggs G F S,Livingstone I,Warren A. The role of streamline curvature in sand dune dynamics:Evidence from field and wind tunnel measurements[J]. Geomorphology,1996,17(1):29-46.
[20]Wiggs G F S,Bullard J E,Garvey B,et al. Interactions between airflow and valley topography with implications for Aeolian sediment transport[J]. Physical Geography,2002,23(5):366-380.
[21]Gao X,Zhang D,Rozier O,et al. Transport capacity and saturation mechanism in a real-space cellular automaton dune model[J]. Advances in Geosciences,2014,37:47-55.
[22]Livingstone I,Wiggs G F S,Weaver C M. Geomorphology of desert sand dunes:A review of recent progress[J]. Earth Science Reviews,2007,80(3):239-257.
[23]张春来,郝青振,邹学勇,等.新月形沙丘迎风坡形态及沉积物对表面气流的响应[J].中国沙漠,1999,19(4):359-363.[Zhang Chunlai,Hao Qingzhen,Zou Xueyong,et al. Response of morphology and deposits to surface flow on windward slope of barchan dune[J]. Journal of Desert Research,1999,19(4):359-363.]
[24]钱广强,董治宝,罗万银,等.横向沙丘背风侧气流重附风洞模拟[J].中国沙漠,2008,28(1):16-20.[Qian Guangqiang,Dong Zhibao,Luo Wanyin. Wind tunnel simulation on flow reattachment on the lee of transverse dunes[J]. Journal of Desert Research,2008,28(1):16-20.]
[25]Jiang H,Dun H,Tong D,et al. Sand transportation and reverse patterns over leeward face of sand dune[J]. Geomorphology,2017,283:41-47.
[26] Watson A. Variations in wind velocity and sand transport on the windward flanks of desert sand dunes[J]. Sedimentology,2010,32(4):581-593.
[27]哈斯,王贵勇.沙丘背风侧气流的变化特征及其意义[J].地理科学,2000,20(6):573-576.[Ha Si,Wang Guiyong. Variation in dune Lee-side airflow and its significance[J]. Scientia Geographica Sincia,2000,20(6):573-576.]
[28] Nickling W G,Neuman C M,Lancaster N. Grainfall processes in the lee of transverse dunes,Silver Peak,Nevada[J]. Sedimentology,2010,49(1):191-209.
[29] Nelson J M,Mclean S R,Wolfe S R. Mean flow and turbulence fields over two-dimensional bed forms[J]. Water Resources Research,1993,29(12):3 935-3 953.
[30]Durán O,Andreotti B,Claudin P. Numerical simulation of turbulent sediment transport,from bed load to saltation[J]. Physics of Fluids,2012,24(10):709-737.
[31]Sauermann G,Kroy K,Herrmann H J. Continuum saltation model for sand dunes[J]. Physical Review E,2001,64(3):031 305.
[32]Walker I J,Nicklingb W G. Dynamics of secondary airflow and sediment transport over and in the lee of transverse dunes[J]. Progress in Physical Geography,2002,26(1):47-75.
[33]葛拥晓,吉力力·阿不都外力,马龙,等.新疆艾比湖干涸湖底沉积物粒径分布及其对风蚀的响应[J].干旱区研究,2014,31(4):636-642.[Ge Yongxiao,Jilili Abuduwaili,Ma Long,et al.Response of granularity distribution to wind erosion in the Playa of the Ebinur Lake,Xinjiang,Northwest China[J]. Arid Zone Research,2014,31(4):636-642.]
[34]李生宇,谷峰,王海峰,等.塔克拉玛干沙漠河湖相沉积平原风蚀地貌发育的外营力作用机制[J].干旱区地理,2012,35(3):358-364.[Li Shengyu,Gu Feng,Wang Haifeng,et al. Exogenic forces action mechanism in the development process of erosion landform on alluvial plains composed of fluvial-lacustrine deposits in the Taklimakan Desert[J]. Arid Land Geography,2012,35(3):358-364.]