资源环境科技发展态势分析平台

The generalized complementary relationship (GCR) model of Brutsaert (2015) has been widely applied to estimate land surface evapotranspiration (E) over Chinese eastern monsoon region, Loess Plateau and Australia. However, Crago et al. (2016, hereinafter C16) recently noted a deficiency in one of his boundary conditions and proposed a novel approach to improve it. The key of this approach is to determine the ratio (x(min)) of the potential evapotranspiration (E-po) to the apparent potential evapotranspiration for an entirely dry surface (E-pads) at which E tends to be vanishing. As seen, the physically reasonable range of x(min) should be between 0 and 1. The present comment reports that the x(min) in C16 may become invalid under conditions of relatively strong available energy but weak winds if E-pads is calculated by the mass-transfer-based method, thereby causing unrealistic estimation of E. A more preferable way to determine E-pads is still based on the traditional Penman-based equation with consideration of the characteristics of dry air in which E-pads occurs.