Abstract:
By Srinivasu Valagerehalli Kalaiah
The Tibetan plateau is a significant heat and momentum source, its energy and water cycles play an important role in the progress of Asian summer monsoon system, which in turn has also significant impact on the spatial-temporal patterns of energy budget over the Tibetan plateau. Due to its complex terrain features, rapidly evolving surface flux densities in terms of net radiation, sensible heat flux, soil heat flux and latent heat flux are multifold and complicated, and vary in space and time due to the dynamic nature of heat transfer processes. The interaction between land surface heat fluxes and monsoon leads to the fact that, higher sensible heat flux and lower latent heat flux were found in the period before monsoon onset over the Tibetan area, dramatically contrary over larger scales. Considering the heterogeneity of land surface in the Tibetan plateau, it is necessary to understand the spatial pattern of surface heat fluxes from pre-monsoon, monsoon to post-monsoon conditions. In this study, the Surface Energy Balance System (SEBS) model proposed by Su (2002) was applied to analyze the characteristics of land surface heat fluxes over the central Tibetan plateau, using CAMP/Tibet 2003 ground observation data combining with MODIS (Moderate-resolution Imaging Spectroradiometer) both Aqua and Terra 2003 images. The regional distribution maps of land surface heat fluxes in terms of net radiation, soil heat flux, sensible heat flux and latent heat flux were analyzed over the central Tibetan plateau for the pre-monsoon, monsoon and post-monsoon periods. The derived SEBS results were validated by using the ground measurements. The results show that, reasonable agreement with the ground measurements during monsoon condition. But for the pre-monsoon and after monsoon periods, SEBS estimate of net radiation was 300 to 400 W/m2 difference with the ground measurements. The latent, sensible and soil heat fluxes of SEBS estimates were also higher than ground measurements with less bias. However, the satellite over pass time and ground data measurements time are not simultaneous, and have different spatial resolutions. Although the phenomenon of energy imbalance in the land surface energy budget over the Tibetan plateau are already debated and are not resolved yet. Finally the limitations and recommendations for the further study were addressed.
Key words: Land surface heat fluxes, MODIS/Terra, Tibetan plateau monsoon condition, SEBS model.