希拉穆仁荒漠草原不同尺度蒸散规律及尺度关系式优化

Law of evapotranspiration at different scales and optimization of scale relationship in Xilamuren desert steppe

以希拉穆仁荒漠草原天然草地为研究对象,利用内蒙古阴山北麓荒漠草原生态水文国家野外科学观测研究站2021年生长季内大孔径闪烁仪(LAS)和涡度相关系统(EC)数据,开展不同时空尺度蒸散规律及LAS与EC尺度关系式在荒漠草原均一下垫面地表可行性研究,并加以优化。结果表明,在2021年生长季内LAS、涡度相关a系统(EC_(a))、涡度相关b系统(EC_(b))累计实测蒸散量(ET)为294、222、251 mm,不同监测方式下呈现ET(LAS)>ET(EC_(b))>ET(EC_(a))趋势,季节性变化明显;EC与LAS源区影响范围位置与大小不同,源区范围均呈“环状”,均从中心向外扩散,贡献能力逐渐递减;研究验证LAS与EC尺度关系式在荒漠草原均一下垫面地表可行性,同时加入作物系数影响加以优化,优化后结果较未考虑作物系数时拟合度提高6.1%,总体较未聚合时提高16.1%,当LAS观测数据受影响而缺失时,可用EC观测结果利用优化后关系式替换。

Taking the natural grassland of Xilamuren desert steppe as the research object, using the large aperture scintillation instrument(LAS) and vorticity correlation system(EC) data of the National Field Observation and Research Station of Desert Steppe Ecohydrology in the North of Yinshan Mountain Inner Mongolia in 2021 growing season, to study the feasibility of evapotranspiration rules at different spatial and temporal scales and the relationship between LAS and EC scales on the uniform underlying surface of desert steppe and to optimize them. The results showed that the accumulated measured(ET) of LAS, vorticity correlation a(ECa) and vorticity correlation b(EC_(b)) in the2021 growing season were 294, 222 and 251 mm, and the trend of ET(LAS) >ET(EC_(b)) >ET(EC_(a)) was observed under different monitoring methods, seasonal variation was obvious. The location and size of the source areas of EC and LAS were different. The source areas of EC and LAS were "circular",spreading from the center to the outside, and the contribution ability gradually decreased. This study verified the feasibility of LAS and EC scale relationship on the uniform surface of desert steppe. At the same time, the effect of crop coefficient was added to optimize the results. The fitting degree of the optimized results was 6.1% higher than that without crop coefficient, and the overall result was 16.1%higher than that without aggregation. When LAS observation data were affected and missing, EC observation results could be used to replace the optimized relationship.