Characteristics of Land-Atmosphere Energy Exchanges over Complex Terrain Area of Southeastern Tibetan Plateau under Different Synoptic Conditions

The geographical environment of the Tibetan Plateau is complex. Previous studies of land surface-boundary layer processes mainly focused on different underlying surfaces without complex topography. The characteristics of land-atmosphere exchanges of energy on different underlying surfaces over complex terrain area of the Tibetan Plateau under different synoptic conditions are analyzed in the present study based on observations collected at four ground sites during May 20th to July 9th 2013 over Linzhi. Results indicate that in the case when the downward shortwave radiation is roughly the same at all the sites, sensible heat flux at the northern slope site, which is covered by broad-leaved forest and characterized by steep terrain, is greater than that at the other three sites; latent heat flux at the southern site, which is covered by wheat and thus with large vegetation fraction, is the largest among the four sites. Energy fluxes show obvious diurnal variation at each individual site. In sunny days, sensible heat flux and net radiation are significantly greater than that in rainy days. However, latent heat flux has little changes under different weather conditions. The influence of complex terrain of the Tibetan Plateau on sensible heat flux is more significant than that of different synoptic conditions. Different topographies have significant impacts on latent heat flux on rainy days. When the warm moist southwesterly flow in front of the South Asia monsoon trough affects Linzhi, the weather will be dominated by cloudy and rainy days. Otherwise sunny days are prevalent in this region. Apparently the variation of monthly land-atmosphere fluxes over Linzhi area is modulated by the South Asia monsoon activities.