不同下垫面空气动力学参数的研究

文中利用中国科学院沙漠研究所与日本国家农业环境技术研究所合作于1990—1994年在中国内蒙古自治区奈曼市半干旱地区沙丘和植被区下垫面观测的微气象数据,根据Monin-Obukhov相似性理论,计算了重度干扰草原、中度干扰草原、轻度干扰草原、无干扰草原、沙丘、沙丘内地、草地、稻田、小麦田、大豆田和玉米田11种下垫面的空气动力学参数粗糙度长度z0,零平面位移d,摩擦速度u*,并分析了它们与水平风速u和Richardson数的关系,比较了不同人为干扰草原生态系统条件下的空气动力学特征。结果表明:地表生物量和覆盖率随着人为干扰强度的增加而减少。不同人为干扰下垫面的粗糙长度与生物量和植被高度以及地表起伏程度有着密切关系;Richardson数也是其影响因子。风速、粗糙度都与摩擦速度成正相关,但对于不同下垫面有所不同,从中可以看到草地对沙漠化有一定的防治作用。同一种下垫面不同时期的空气动力学参数也存在差异。这些结果对建立陆面过程和区域气候模式具有重要的意义。

STUDY OF AERODYNAMIC PARAMETERS FOR DIFFERENT UNDERLING SURFACES

Zero-plane displacement(d),roughness length(z_0),friction velocity(u_*) for the heavy grazing site,moderate grazing site,light grazing site,no grazing site,dune,inter-dune,grassland,paddy field site,wheat site,soybean site,and maize site etc underlying surfaces have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorological observation data of the dune and vegetation underlying surfaces in the semi-arid area in Naiman city, Inner Mongolia of China,conducted jointly by the Institute of Desert Research of CAS and the National Institute of Agro-Environmental Sciences of Japan in 1990-1994,and their relationships with horizontal wind speed and Richardson number analyzed,and the aerodynamic characteristics for different underlying surfaces under the conditions of different anthropogenically disturbed grassland ecosystems also compared.Results show that the vegetation coverage and above-ground biomass decrease with the increase in the anthropogenically disturbed extent of grassland ecosystem.The roughness length for different anthropogenically disturbed underlying surfaces is close related with biomass,vegetation height,and ground surface undulation,and Richardson number R_i is also its influence factor.The friction velocity is positively proportional to wind speed and roughness length,but to different extent for different underlying surfaces.The aerodynamic parameters of the same underling surface are different,too,in different growth seasons.The above results indicate that grassland and vegetation are of significance in preventing the desertification,especially in the arid and semi-arid land ecosystem region.And the results of this paper are also important for constructing the land surface process as well as regional climate model.