科研之友
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摘要
Lake-atmosphere temperature difference (?T) plays an important role in the heat exchange between lake surface and overlying atmosphere during the ice-free period. However, due to the difficulty of carrying out field observation experiments on the Qinghai-Xizang Plateau (QXP), the characteristics of the ?T remains poorly understood. And also, there are few studies on the radiation and energy budget of the alpine lakes at present. In this study, the characteristics of ?T, radiation and energy balance at three larger and deeper alpine lakes with different depths (Ngoring, Bangong Co and Nam Co) were studied by using the China Meteorological Forcing Dataset (ITPCAS) and the one-dimensional lake module of the Community Land Model (CLM-Lake) . Verification of model results achieved with remote sensing data and observed data from meteorological station indicate that the lake model has a good ability in simulating the seasonal variations of the lake surface temperature on the QXP. As a result of the lower temperature and the stronger solar radiation caused by high altitude on the QXP, the ?T of Ngoring (23 m deep) and Nam Co (95 m deep) were always positive during the ice-free period and continued to increase from the late spring or early summer to the late autumn or early winter. Available observations and the simulations in our study showed that the Bangong Co lake, with a depth of 37 m, has a negative ?T in June and July, which may ascribed to a warmer and drier air in Bangong Co lake region in June and July, lead to a stronger evaporation over the lake surface, and more energy of the lake was released in the form of latent heat. As a result, the warming of the lake surface was weakened and slower than air temperature, eventually a negative ?T formed. This phenomenon is different from other lakes in QXP during the ice-free period where the ? T is generally positive. However, it should be noted that the observed lake water temperature at Bangong Co is 5 m below the lake surface and air temperature is over the land surface 10 km away from the lake, so more accurate data is needed for the further verification. The trend of the simulated sensible heat flux over surface of the three lakes was similar to that of ?T, and the simulated latent heat flux was positive all year round meaning that the lake was constantly sending water vapor to the atmosphere.
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