Estimation of key surface parameters in semi-arid region and their impacts on improvement of surface fluxes simulation (2016)


These key parameters are related to soil moisture and heat transfer and physical processes in the vegetation canopy as well as other important aerodynamic processes. In Liu et al. (2016), measurements of surface-atmosphere interaction at two observation stations that are located in the typical semi-arid region of China, Tongyu Station in Jilin Province and Yuzhong Station in Gansu Province, are combined with the planetary boundary layer theory to estimate surface roughness length z0m and excess resistance kB-1. Multiple parameterization schemes have been used in the study to obtain values for surface roughness length and excess resistance kB-1 at the two stations. Results indicate that z0m has distinct seasonal and inter-annual variability. kB-1 demonstrates a significant diurnal variation and seasonal variability. Using the modified scheme for the estimation of z0m and kB-1 in the land surface model, it is found that simulations of sensible heat flux over the semi-arid region have been greatly improved.

Figure 1 Simulated and observed diurnal variation of kB-1. (a) growing season at Tongyu farmland site; (b) non-growing season at Tongyu farmland site; (c) degraded grassland site of Tongyu site; (d) Yuzhong Station.

Figure 2 Observed and Simulated sensible heat flux over the three study sites. For each, EX1 is with the original parameter setting, EX2 includes estimated z0m, EX3 further includes estimated kB-1 on the bases of EX2.

Li, W., Guo, W. (*), Xue, Y., Qiu, B. and Fu, C.: Sensitivity of a regional climate model to land surface parameterization schemes for East Asian summer monsoon simulation, Clim. Dynam., 47, 2293–2308, doi: 10.1007/s00382-015-2964-8, 2016.