Global Lake Evaporation Estimates by Integrating Penman Method with Equilibrium Temperature Approach

Modeling evaporation ( E ) from inland water bodies is challenging largely due to the uncertainties of input data, particularly surface water temperature that plays a key role in the available energy, i.e. net radiation ( R n ) minus rate of water heat storage change G . The equilibrium temperature approach (ETA) for estimating water surface temperature offers an alternative method to calculate R n and G using standard meteorological data. This study evaluates the global lake E estimates from the widely used Penman model (PM) coupled with the ETA (PM-ETA) against field observations and model simulations from the Lake, Ice, Snow, and Sediment Simulator (LISSS). Our analysis reveals that the PM-ETA tends to overestimate E by approximately 36% and 24% compared to observations and the LISSS simulations, respectively, despite being driven by the same input data. The biases of the PM-ETA E are more pronounced in the cold and polar regions with distinct seasonality of R n and G . Furthermore, the E trends from the PM-ETA deviate from the LISSS simulations over the period of 2001 to 2016 due to the bias trends in the available energy. By incorporating the LISSS-simulated R n and G into the PM, the bias in E is reduced to less than ±5% compared to the LISSS results. This study highlights the need to improve the available energy input of the PM to improve the estimates of global Lake E for better water resource management and planning.