西北干旱区荒漠生态系统通量贡献区模型研究

A Footprint Analysis on a Desert Ecosystem in West China

涡度相关仪通量值所代表的通量贡献区范围,对于通量观测塔的选址、仪器安装高度的确定以及通量观测数据的质量控制等具有重要的指导意义。利用通量贡献区模型对位于古尔班通古特沙漠试验场通量观测资料的空间代表性进行初步分析。结果表明:该荒漠区在大气稳定条件下90%的通量贡献区最远可以达到686.40m,通量贡献函数最大点的位置在162.50m;大气稳定时各风向的通量贡献区范围在生长末期均达到最大,生长初期和中期的源区变化因受到各风向风速和植被下垫面的影响而有差异;大气不稳定时不同生长时期各风向通量贡献区没有固定变化规律;通量源区大约有58.71%的信息来自于荒漠区通量观测塔西南至西北方,整个生长季生长末期通量贡献最多,所占比例为40.16%。由FSAM模型测得的通量贡献区范围可以较准确地反映荒漠生态系统下垫面的通量信息。

Footprint analysis is essential for eddy covariance tower site selection, quality-control and data-in- terpretation. But only a few of such studies are available in the western China arid region till now. This study aims to fill the empty up by utilizing the FSAM Model （Flux Source Area Model） to analyze the spatial representation of flux measurements in this region. Flux data in the Gurbantunggut Desert Remote Sensing Experimental Station was used in this study. Results revealed that under stable atmospheric conditions, the far end of the source area reached 680.40 m with the maximum contribution source located at 162.50 m （at a 0. 9 significant level）. Variations of source area in different phenological stages were preliminary due to different wind directions when under similar conditions of atmospheric stability from the beginning to the mid-term of season, even the largest source areas were all found at the end of season ignorant of wind direc- tions. Furthermore, under different conditions of atmospheric stability the source area are inconsistent in different wind directions. About 58. 71% of flux came from the southwest to northwest of the tower with a contribution estimated to be as high as 40. 16% at the end of growth period under the stable and unstable conditions. Our study suggests that our carbon dioxide flux data adequately revealed the characteristics of surface flux with desert ecosystem.