Radiative and Aerodynamic Contribution to Evaporation: Eddy-Covariance Comparison Between a Plain and a Plateau Lake

Water surface-atmosphere interactions play an important role in the climate system on regional and even global scale. Yet, it remains unclear whether radiative or aerodynamic forces contribute more to water surface evaporation, which may lead to different strategies in model parameterization. This study compared the eddy covariance observations taken at two contrasting lakes in China: Poyang Lake (subtropical, plain, and warm) in 2018 and Yamzhog Yum Co (alpine, plateau, and cold) in 2016. Both lakes of similar latitude have similar solar radiation, and Yamzhog Yum Co has a lower atmospheric pressure and air density and a larger temperature difference between water surface and air. Poyang Lake had a total evaporation of 741 mm from 6 May to 31 December 2018, relatively higher than that of Yamzhog Yum Co (677 mm) for the same season in 2016. Evaporation peaked in August for Poyang Lake but in October for Yamzhog Yum Co. The Penman equation disclosed that radiative forces contributed more than aerodynamic forces in both lakes. Evaporation was found to be most sensitive to air temperature in Poyang Lake but to surface net radiation in Yamzhog Yum Co, attributable to their sensitivity differences in iso-radiative and isothermal conditions. Higher elevation reduced the aerodynamic contribution with lower air temperature and atmospheric pressure in Yamzhog Yum Co. The findings should be useful for understanding different behaviors of lake evaporation under common mechanisms.