Diagnosis of Atmospheric Drivers of High-Latitude Evapotranspiration Using Structural Equation Modeling
Diagnosis of Atmospheric Drivers of High-Latitude Evapotranspiration Using Structural Equation Modeling
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DOI：
10.3390/atmos12101359
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发表时间：
2021-10
期刊：
影响因子：
2.9
通讯作者：
Sarah M. Thunberg;E. Euskirchen;J. Walsh;Kyle M Redilla
中科院分区：
文献类型：
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作者：
Sarah M. Thunberg;E. Euskirchen;J. Walsh;Kyle M Redilla
蒸散（ET）是地表水分收支的一个相关组成部分，与不同的驱动因素有关。相互关联的驱动因素导致每日至年际时间尺度的变化。本研究使用结构方程模型来诊断的驱动程序超过45个高纬度站点，每个站点提供至少几年的原位测量，包括潜热通量来自涡动协方差通量塔的合奏。这些地点按植被类型（苔原、森林）和有无永久冻土进行分组，以确定不同驱动因素的相对重要性如何取决于地表特征。因子分析用于量化变量之间的共同方差，而路径分析程序用于评估不同变量的独立贡献。在森林站点的ET的变化一般表现出较强的相对湿度的依赖性，而ET在苔原网站是更多的温度限制比水分限制。通径分析表明，蒸散量与太阳辐射的直接相关性最强。风速对ET变化的独立贡献最大。太阳辐射的独立贡献较小，因为太阳辐射还通过各种其他驱动因素影响ET。在森林湿地，风速的独立贡献尤其明显。对于冻土带和森林植被，温度负荷较高的第一个因素时，冻土存在，这意味着ET将成为不太敏感的温度作为冻土融化。
Evapotranspiration (ET) is a relevant component of the surface moisture budget and is associated with different drivers. The interrelated drivers cause variations at daily to interannual timescales. This study uses structural equation modeling to diagnose the drivers over an ensemble of 45 high-latitude sites, each of which provides at least several years of in situ measurements, including latent heat fluxes derived from eddy covariance flux towers. The sites are grouped by vegetation type (tundra, forest) and the presence or absence of permafrost to determine how the relative importance of different drivers depends on land surface characteristics. Factor analysis is used to quantify the common variance among the variables, while a path analysis procedure is used to assess the independent contributions of different variables. The variability of ET at forest sites generally shows a stronger dependence on relative humidity, while ET at tundra sites is more temperature-limited than moisture-limited. The path analysis shows that ET has a stronger direct correlation with solar radiation than with any other measured variable. Wind speed has the largest independent contribution to ET variability. The independent contribution of solar radiation is smaller because solar radiation also affects ET through various other drivers. The independent contribution of wind speed is especially apparent at forest wetland sites. For both tundra and forest vegetation, temperature loads higher on the first factor when permafrost is present, implying that ET will become less sensitive to temperature as permafrost thaws.