Long-term eddy covariance flux observations over complex topography are crucial for improving the understanding of the turbulent exchanges between the land and atmosphere. Based on a 12-year (2007–2018) record dataset measured with the eddy covariance technique over the Dali agriculture ecosystem in the southeastern margin of the Tibetan Plateau, we investigated the diurnal, seasonal, and interannual variations of the sensible heat flux (Hs), latent heat flux (LE), and carbon dioxide flux (Fc), and their controlling variables. The results showed that Hs and LE exhibited similar diurnal and seasonal variations, while the amplitude of LE was clearly larger than that of Hs throughout the year. The turbulent fluxes showed remarkable fluctuation on the annual scale. The annual average Hs (LE) increases (decreases) from approximately 8 (110) W·m⁻² during 2007–2013 to 20 (79) W·m⁻² during 2014–2018. The annual cumulative net CO₂ ecosystem exchange (NEE) increases significantly from approximately −739 g·C·m⁻²·yr⁻¹ during 2007–2013 to −218 g·C·m⁻²·yr⁻¹ during 2014–2018. The relationship between turbulent fluxes and meteorological variables was also examined. Wind speed (WS) is found to be the dominant controlling factor for the Hs on different temporal scales and their correlation coefficients increase when the timescales vary from daily to annual scale; whereas the product of WS and vapor pressure deficit (VPD) is the major meteorological variable controlling the LE over all temporal scales. The net radiation (Rn) is the dominating factor for Fc on daily and monthly timescales, while WS becomes the most controlling factor for Fc on an annual scale. Notably, surface energy and CO₂ fluxes are also greatly influenced by the vegetation cover surrounding the measurement site.

中文翻译：

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青藏高原东南缘农业生态系统的长期（2007 年至 2018 年）能量和 CO2 通量

对复杂地形的长期涡度协方差通量观测对于提高对陆地和大气之间湍流交换的理解至关重要。基于青藏高原东南缘大理农业生态系统12年（2007-2018）涡度协方差记录数据集，研究感热通量（Hs）的日变化、季节变化和年际变化)、潜热通量 (LE) 和二氧化碳通量 (Fc) 及其控制变量。结果表明，Hs和LE表现出相似的日变化和季节变化，而LE的振幅全年明显大于Hs。湍流通量在年尺度上表现出显着的波动。年平均 Hs (LE) 从大约 8 (110) W·m 增加（减少）^{2007-2013 年期间的−2}到 2014-2018年期间的 20 (79) W·m ^{−2 。}每年累积的净 CO ₂生态系统交换 (NEE) 从 2007-2013 年的大约 −739 g·C·m ⁻² ·yr ⁻¹显着增加到 −218 g·C·m ⁻² ·yr ⁻¹2014-2018 年期间。还检查了湍流和气象变量之间的关系。发现风速（WS）是不同时间尺度上 Hs 的主要控制因素，并且当时间尺度从日尺度到年尺度变化时，它们的相关系数增加；而 WS 和水汽压差 (VPD) 的乘积是在所有时间尺度上控制 LE 的主要气象变量。净辐射 (Rn) 是 Fc 在日和月时间尺度上的主导因素，而 WS 在年尺度上成为 Fc 的最主要控制因素。值得注意的是，地表能和 CO ₂通量也受到测量点周围植被覆盖的很大影响。