报告题目：Estimation and Seasonal Variation of Evapotranspiration above a Humid Forest

报告人：谢正义 副教授，台湾大学

邀请人：张权 博士

时  间：2019年9月4日（星期三）下午3:00—5:00

地  点：国家重点实验室学术报告厅（农水楼一楼）

报告人简介：  

     谢正义副教授博士毕业于杜克大学，现任职于台湾大学生物环境系统工程系。谢正义副教授的研究主要涉及环境生物物理学、环境流体力学、环境生物物理量测等。

报告简介：

      This study presented a two-year data set of sensible heat and water vapor fluxes above a humid subtropical montane Cypress forest, located at 1650 m a.s.l. in northeastern Taiwan. The focuses of this study were to investigate 1) the diurnal and seasonal variations of canopy resistance and fluxes of sensible heat and water vapor above this forest; and 2) the mechanism of why a fixed canopy resistance could work when implementing the Penman-Monteith equation for diurnal hourly evapotranspiration estimation.

Our results showed distinct seasonal variations in canopy resistance and water vapor flux, but on the contrary, the sensible heat flux did not change as much as the water vapor flux did with different seasons. The seasonal variation patterns of the canopy resistance and water vapor flux were highly coupled with the meteorological factors. Also, the results demonstrated that a constant (fixed) canopy resistance was good enough for estimating the diurnal variation of evapotranspiration using Penman-Monteith equation. We observed a canopy resistance around 190 (s/m) for both the two warm seasons; and canopy resistances were around 670 and 320 (s/m) for the two cool seasons, respectively.        In addition, our analytical analyses demonstrated that when the average canopy resistance is higher than 200 (s/m) and under a general meteorological condition, the Penman-Monteith equation is less sensitive to the change of canopy resistance; hence, a fixed canopy resistance is suitable for the diurnal hourly evapotranspiration estimation. However, this is not the case when the average canopy resistance is less than 100 (s/m), and variable canopy resistances are needed. These two constraints (200 and 100) were obtained based on purely analytical analyses, and can be applied to any kind of vegetation surface.  

     欢迎相关专业教师和研究生的光临！