半干旱区土壤热量传递的慢过程对地表能量平衡的影响

Effect of Soil Heat Slow Transmission Process on Surface Energy Balance in Semi-Arid Area

地表能量不平衡是陆面过程研究中普遍遇到的问题。利用黄土高原陆面过程试验的观测资料,研究了半干旱区热量在土壤中的缓慢传递过程(简称"慢过程")对地表能量平衡的影响。结果如下:(1)热量在土壤浅层线性传递,30 min内传递厚度约为1.5 cm;(2)基于慢过程,提出了计算土壤热储、土壤热通量和地表土壤热通量的传输线、四边形和三角形等3套方法,并给出了其公式;(3)3套方法得到的地表能量闭合度在上半天高于或接近不考虑慢过程的常规法,下半天与整个白天低于或接近常规法;(4)常规法在一定程度上存在上半天低估、下半天高估、整个白天也高估土壤热通量、土壤热储、地表土壤热通量及闭合度的缺点。所以,在半干旱区,考虑慢过程并选用合适的方法不仅可提高或维持闭合度水平,还可克服常规法的缺点。

The unclosure of surface energy is a common problem in the study of the land surface process. The authors think that the slow transport process of heat （STP） existing in soil may influence the unclosure to some extent. The influence of the process in semi-arid area is studied using observational data which are observed in the Experimental Study of Land Surface Processes in Chinese Loess Plateau. The results are as follows. （1） Heat is transported linearly in the shallow soil layer and only reaches 1.5-cm soil depth within 30 rain; （2） Three approaches, namely, transport line approach, quadrilateral approach and triangle approach, are proposed on the base of the STP. And the equations of the three approaches are also given; （3） The surface energy closure degrees （SECD） of the three approaches in the 1st half-day are bigger than or similar to the traditional method without consideration of STP, while thosein the 2nd half-day and whole daytime are similar to or less than the traditional approach without consideration of the STP; （4） The traditional approach has a flaw of underestimation of the 1 st half-day and overestimations of the 2nd half day and whole day about the soil heat flux, soil heat storage, ground heat flux and SECD. So, when the quadrilateral approach is adopted in semi-arid area, the introduction of the STP can overcome the flaw of the traditional approach as well as improving the SECD or keeping the SECD.