An investigation into the surface energy balance on the southeast edge of the Tibetan Plateau and the cloud’s impact

The Tibetan Plateau and the 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 characteristics of the 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-G0）, showing the basic feature of SEB closure, but there still was a discrete phenomenon of SEB non-closure, especially in the surface layer where the feature of SEB non-closure became more obvious with increasing surface flux and available energy. The low cloud cover in the southeastern part (Dali, Linzhi) 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 the low cloud cover and the 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 on 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 waveradiation associated with low clouds might be one of the important influential factors for the occurrence of the near-solar constant phenomenon in radiation observation in the plateau.