Characters Of Surface Energy Balance On The Southeast Edge Of Tibetan Plateau And Cloud's Impact

The Tibetan Plateau and Loess Plateau in spring and summer are the high value areas of solar total radiation and land-air temperature difference, as well as the anomalous areas of cloud covers in China. The structural characters of surface energy balance (SEB) components in the Tibetan Plateau and the Sichuan Basin are investigated in this paper using the boundary layer integrated system observations at Dali, Linzhi, and Wenjiang flux station, from the angle of energy balance, to further understand the impact of clouds'status on the SEB components. The study indicates that on the southeast edge (Dali, Linzhi, Wenjiang) of the Tibetan Plateau, the sensible and latent heat (H+LE) were significantly correlated with the available energy (Rn-GO), i.e. there was the basic character of SEB closure, however, there also was a discrete phenomenon of SEB imclosure, especially the imclosure character of SEB became more obvious with increasing surface flux and available energy in the surface layer. The low cloud cover in the southeast (Dali, Llnzhi) of the Tibetan Plateau in spring and summer was significantly negatively related with the surface sensible heat flux, but its correlation with the latent heat flux was weak and uncertain.The correlation between low cloud cover and sensible heat flux in spring was more significant in the southeast edge (Dali, Linzhi) than in the Sichuan Basin region (Wenjiang); and the low cloud in the plateau region played a "cooling" role in the surface layer energy budget and the low cloud cover was significantly positively correlated with the downward long-wave radiation. This result describes the heating feedback effect of the radiation forcing of low clouds to the land surface, i.e. the low cloud status in the Tibetan Plateau could be indirectly expressed with the downward long-wave radiation fluxes observed at flux towers. The analyses of the observations also suggest that the impact of low clouds on the SEB at Wenjiang station situated in the Chengdu plain was far less than that in the Tibetan Plateau. The research results suggest that high value areas of the downward long wave radiation associated with low clouds might be one of important influential factors for the occurrence of the near-solar constant phenomenon in radiation observation in the plateu.