Surface energy budget and closure of the eastern Tibetan Plateau during the GAME-Tibet IOP 1998

Turbulent flux measurements based on the eddy correlation technique were conducted on the Tibetan Plateau during the Intensive Observation Period (IOP) of the GEWEX Asian Monsoon Experiment (GAME) in 1998. This paper presents on analysis of the surface energy budget and its closure at the Amdo planetary boundary layer site in the eastern Tibetan Plateau using GAME-Tibet IOP data. A seasonal variation in the surface energy closure ratio (CR) was seen. CR was higher than 0.8 in the pre-rnonsoon period and after DOY 233, when the infrared hygrometer was performing satisfactorily. However, CR was lower than 0.7 throughout most of the summer monsoon, due at least in part to degraded performance of the infrared hygrometer under heavy precipitation. In addition, through detail analysis of the diurnal variations of surface energy flux for the best-CR period of September 4-6, it was found that the melting and freezing of near-surface soil moisture plays a significant role in the variation of surface energy fluxes, particularly in terms of latent heat flux. The calculated effective mass of melting and freezing water in one day was 3.3-3.9 kg/m^2, which is comparable to the daily total.