Aims

Quantitative characterization of the time-lag effect between canopy temperature and atmospheric temperature and its controlling factors in the agricultural ecosystem may contribute to a higher inversion accuracy of soil water content using canopy-air temperature information.

Methods

Tc of winter wheat were continuously monitored, and the data of such environmental factors as solar radiation (Rs), atmospheric temperature (Ta), relative humidity (RH) and soil water content (SWC) were simultaneously collected.

Results

Hysteresis existed between Tc and Ta over the diel cycles, and different weather and irrigation levels did not change the direction of the time lag loop. the key driver regulating the diel hysteresis pattern between Tc and Ta varied under different weather: on rainy days, key driver was Rs while on cloudy and sunny days, the key driver was RH. the multiple regression model indicated that together Rs, Ta, RH, and SWC explained 58 ± 10% of the variation of time-lag effect. Path analysis showed on rainy days the key driver (Rs and RH) could enhance the time-lag effect through other indirect factors (Ta and SWC); on cloud days the key driver (RH and SWC) could inhibit the time-lag effect through other indirect factors (Ta); On sunny days this mutual inhibition was further significant.

Conclusions

These findings indicated a dynamic process of time-lag effect between Tc and Ta with different weather and different irrigation levels. This study contributes to the understanding of the time-lag effect and its driving factors and this analysis provides the basis for further improvement in monitoring crop water deficit.

中文翻译：

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冬小麦冠层温度与大气温度的滞后及其驱动因素

目标

定量表征冠层温度与大气温度之间的时滞效应及其在农业生态系统中的控制因素可能有助于利用冠层-气温信息提高土壤含水量的反演精度。

方法

持续监测冬小麦的Tc，同时采集太阳辐射（Rs）、大气温度（Ta）、相对湿度（RH）和土壤含水量（SWC）等环境因子数据。

结果

Tc和Ta在昼夜周期内存在滞后现象，不同的天气和灌溉水平并没有改变时间滞后环的方向。调节Tc和Ta之间的diel滞后模式的关键驱动因素在不同天气下有所不同：雨天关键驱动为Rs，阴天和晴天关键驱动为RH。多元回归模型表明，Rs、Ta、RH 和 SWC 共同解释了 58 ± 10% 的时滞效应变化。路径分析显示，雨天关键驱动因素（Rs 和 RH）可以通过其他间接因素（Ta 和 SWC）增强时滞效应；在阴天，关键驱动因素（RH 和 SWC）可以通过其他间接因素（Ta）抑制时滞效应；在阳光明媚的日子里，这种相互抑制更加显着。

结论

这些发现表明，在不同天气和不同灌溉水平下，Tc 和 Ta 之间存在时间滞后效应的动态过程。本研究有助于理解时滞效应及其驱动因素，该分析为进一步改进作物缺水监测提供了基础。