Carbon dioxide, latent and sensible heat fluxes were measured by means of the eddy covariance method above a mountain meadow situated on a steep slope in the Stubai Valley in Austria, based on the hypothesis that, due to the low canopy height, measurements can be made in the shallow equilibrium layer where the wind field exhibits characteristics akin to level terrain. In order to test the validity of this hypothesis and to identify effects of complex terrain in the turbulence measurements, data were subjected to a rigorous testing procedure using a series of quality control measures established for surface-layer flows. The resulting high quality dataset comprised 36% of the original observations, the substantial reduction being mainly due to a change in surface roughness and associated fetch limitations in the wind sector dominating during nighttime and transition periods. The validity of the high quality dataset was further assessed by two independent tests: (i) a comparison with the net ecosystem carbon dioxide exchange measured by means of ecosystem chambers, and (ii) the ability of the eddy covariance measurements to close the energy balance. The net ecosystem CO2 exchange measured by the eddy covariance method agreed reasonably well with ecosystem chamber measurements. The assessment of the energy balance closure showed that there was no significant difference in the correspondence between the meadow on the slope and another one situated on flat ground at the bottom of the Stubai Valley, available energy being underestimated by 28% and 29%, respectively. We thus conclude that, appropriate quality control provided, the eddy covariance measurements made above a mountain meadow on a steep slope are of similar quality as compared to flat terrain.

中文翻译：

---

山坡草甸上方二氧化碳、潜能和显能通量的涡度协方差测量

二氧化碳、潜热和感热通量是通过位于奥地利斯图拜山谷陡坡上的山地草甸上方的涡度协方差法测量的，假设假设由于冠层高度较低，可以进行测量在浅平衡层，风场表现出类似于平坦地形的特征。为了检验这一假设的有效性并确定复杂地形对湍流测量的影响，使用为表层流动建立的一系列质量控制措施对数据进行了严格的测试程序。由此产生的高质量数据集包含原始观测值的 36%，大幅减少主要是由于表面粗糙度的变化以及在夜间和过渡期间占主导地位的风能部门的相关获取限制。通过两个独立测试进一步评估了高质量数据集的有效性：（i）与通过生态系统室测量的净生态系统二氧化碳交换进行比较，以及（ii）涡流协方差测量关闭能量平衡的能力. 通过涡度协方差法测量的净生态系统 CO2 交换与生态系统室测量值相当吻合。能量平衡闭合评估表明，斜坡上的草地与位于斯图拜谷底部平坦地面上的草地之间的对应关系没有显着差异，可用能源分别被低估了 28% 和 29%。因此，我们得出结论，在提供适当的质量控制的情况下，与平坦地形相比，在陡坡上的山地草地上进行的涡流协方差测量具有相似的质量。