The surface energy budget and evapotranspiration in the Tanggula region on the Tibetan Plateau

The sensible and latent heat fluxes in the Tanggula region were calculated using turbulent flux monitoring data from June 2004 to December 2005. The monitoring site was located on a gentle slope covered by meadow vegetation (91°56′E, 33°04′N; elevation 5100 m). The turbulent flux monitoring was conducted using the eddy covariance system and a meteorological gradient tower. The results indicated that the average surface energy closure ratio (CR) was 1.07 for the period from June to December of 2004, and 1.03 for the year 2005. The surface energy balance was greatly influenced by rainfalls, snowfalls and snow cover. The sensible heat flux was higher in spring and had a heat sink in summer due to the heat consumed in thawing of the active layer. The latent heat flux was much higher in summer because the soil moisture content was higher, resulting from the thawing of the active layer and more precipitation during the summer monsoon season. It also was found that the amplitudes of the energy fluxes on cloudy days were lower than that on clear days. The evapotranspiration was well related to the surface soil moisture content. The freezing and thawing cycles played a significant role in the land surface processes.