沙漠-绿洲过渡带近地表风沙动力过程研究

Controlled by the landscape pattern of oasis and desert，the processes of wind-blown sand in the oasis-desert transitional zone have direct impacted on the stability and development of oasis. Local circulation and microclimate induced by the gradient differences of environment factors between oasis and desert such as vegetation, relief, underlying surface, hydrographic and meteorological factors and so on have restricted the back and forward of desert or the transition of oasis. In our present study, a typical oasis-desert transitional zone in Dunhuang Oasis at the east of Kumtagh Desert will be selected as our studying site. With the methods of setting section from desert to oasis, fixed point observation in the field, wind tunnel experiment and numerical simulation, this research focuses on local circulation between oasis and desert, flow field near surface and their influences on the process of wind-blown sand in the oasis-desert transitional zone. The primary objects of this research are to clarify the characters of wind-dynamical environments, to build a two-dimension theoretical model on the erosion-accumulation process of wind-blown sand, and to reveal the sand transport laws near earth surface in the oasis-desert transitional zone. This research will not only broaden the research spectrum of sand physics and enrich the theoretical system of desert science, but also solve the sand damages problems and ensure ecological safety of oasis. Moreover, it will provide scientific evidence for establishing the oasis-protection system in arid region，which is both significant in theory and in practice.

受绿洲和沙漠景观格局的双重影响，沙漠－绿洲过渡带近地表风沙过程及其动态演变直接影响绿洲的稳定和有序发展。地表物质组成、植被、地貌、水文和气候等环境要素在沙漠和绿洲间的梯度差异造成的局地环流和小气候，在空间上制约沙漠的进退或绿洲的变迁。 鉴于此，本项拟选择地处库姆塔格沙漠东缘的敦煌绿洲，自沙漠向绿洲设置风沙定点监测断面，通过野外定位梯度监测、风洞实验与数值模拟，研究沙漠－绿洲过渡带局地环流特征、近地表流场及其对风沙输移的影响，阐明沙漠－绿洲过渡带风动力环境特征，建立近地表风沙蚀积过程的二维理论模式，揭示沙漠－绿洲过渡带近地表风沙输移规律。此项研究不仅拓展风沙物理学研究领域和丰富沙漠与绿洲科学理论体系，而且有助于解决绿洲风沙危害，确保沙漠绿洲的生态安全，更能为干旱区绿洲风沙防护体系建设提供理论依据，具有重要的理论和实践意义。

沙漠绿洲过渡带是一个对外界条件变化极为敏感的生态环境脆弱带，沙漠绿洲过渡带近地表风沙过程不仅影响区域生态环境演变和沙漠绿洲系统稳定，也是辨析区域沙漠化或绿洲化的关键，在空间上制约沙漠的进退或绿洲的变迁。受本项目资助，共发表论文17篇，其中，SCI收录论文3篇；获批授权专利10项（发明专利2项）；培养硕士研究生3人，协助培养博士研究生1人；项目负责人分别获甘肃省科技进步一等奖（R8）、中科院科技促进发展奖（R4）、全国青年地理科技奖、青藏高原青年科技奖、中科院“西部之光”人才项目和中科院青年创新促进会会员。项目研究成果主要包括（1）阐明了沙漠绿洲过渡带局地环流特征：在昼夜和季节尺度上，揭示了“绿洲风”和“沙漠风”特征参数的时空分布规律，受地表水热、地形和景观格局等影响，夏季白天，绿洲风强于沙漠风，夜晚绿洲风弱于沙漠风，冬季反之，沙漠绿洲过渡带昼夜和季节局地环流明显；（2）揭示了沙漠绿洲过渡带起沙风、输沙势、风沙通量等风动力参数的时空分布特征：沿沙漠至绿洲方向，输沙势DP分别为204 VU、51.7 VU和1.4 VU；年起沙风频次分别为24475、8312、301；过渡带和绿洲平均风速较沙漠减小约22.2%和50.2%；摩阻速度和输沙率均呈递减趋势，动力学粗糙度增大；（3）阐明了沙漠绿洲过渡带近地表风沙蚀积过程：从典型风况、风季、非风季和年际四个时间尺度，揭示了沙漠绿洲过渡带近地表输沙量、风沙流结构、沉积物粒度特征和沙丘形态特征参数等动态变化规律；受沙源供给和局地环流影响，沙漠绿洲过渡带风沙活动呈往复式运移，沙漠绿洲过渡带对绿洲保护起到重要的缓冲和屏障作用；（4）建立了一个近20平方公里的沙漠绿洲过渡带野外固定风沙观测场，累积获取风沙监测相关数据量超过30 G。研究成果不仅拓展了风沙物理学研究领域和丰富沙漠与绿洲科学理论体系，而且有助于解决绿洲风沙危害，确保沙漠绿洲的生态安全，更能为干旱区绿洲风沙防护体系建设提供理论依据，具有重要的理论和实践意义。