The surface energy budget in the permafrost region of the Tibetan Plateau

摘要

Data observed at monitoring stations in the Tanggula Pass (TGLMS) and in the Xidatan region (XDTMS) were used to calculate the surface energy fluxes, that is, net radiation, ground surface heat flux, sensible heat flux, and latent heat flux. The energy closure statuses obtained by the daily accumulated energy fluxes at the TGLMS and XDTMS sites were good and the turbulent fluxes were slightly higher than the available energy, but this was influenced by differing timescales. From an energy perspective, the phenomenon of turbulent fluxes being greater than the available energy is advantageous to the development of permafrost, and snow cover is advantageous to storing cold energy in soil. The sensible heat flux and the latent heat flux exhibited a seasonal alternation characteristic, that is, the sensible heat flux was higher than the latent heat flux in winter and spring, but was lower than the latent heat flux in summer and autumn. This is mainly related to the precipitation influenced by the monsoon and the freezingthawing processes of the active layer. Analysis of diurnal flux variations included the daily freezing-thawing processes. Variations of the Bowen ratios at the two sites were greater than 1.0 from June to September, and less than 1.0 in the other months. Negative Bowen ratios appeared when the snow cover reached a certain thickness (in this case, 10 cm).