Journal ArticleGlobal Lake Evaporation Estimates by Integrating Penman Method with Equilibrium Temperature ApproachFarooq, Umar; Liu, Heping; Zhang, Qianyu; Wang, Jingfeng; Shen, Lian<title>Abstract</title> Modeling evaporation<italic>E</italic>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<italic>Rn</italic>minus rate of water heat storage change<italic>G</italic>. The equilibrium temperature approach (ETA) for estimating water surface temperature offers an alternative method to calculate<italic>Rn</italic>and<italic>G</italic>using standard meteorological data. This study evaluates the global lake<italic>E</italic>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<italic>E</italic>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<italic>E</italic>are more pronounced in the cold and polar regions with distinct seasonality of<italic>Rn</italic>and<italic>G</italic>. Furthermore, the<italic>E</italic>trends from the PM-ETA deviate from the LISSS simulations over the period of 2001–16 due to the bias trends in the available energy. By incorporating the LISSS-simulated<italic>Rn</italic>and<italic>G</italic>into the PM, the bias in<italic>E</italic>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<italic>E</italic>for better water resource management and planning. <sec><title>Significance Statement</title>This study addresses a crucial challenge in modeling evaporation<italic>E</italic>from inland water bodies—uncertainties in surface water temperature and available energy inputs, particularly net radiation<italic>Rn</italic>and rate of heat storage change<italic>G</italic>. By evaluating the widely used Penman model (PM) coupled with the equilibrium temperature approach (ETA), we reveal a tendency for the PM-ETA to overestimate<italic>E</italic>globally, with the largest biases observed in cold and polar regions. Incorporating higher-quality<italic>Rn</italic>and<italic>G</italic>estimates from the Lake, Ice, Snow, and Sediment Simulator (LISSS) significantly reduces these biases. These findings highlight the importance of alternative higher-quality data products for available energy inputs for improving<italic>E</italic>estimates by the PM.</sec>American Meteorological Society2025-09-1510636037Journal of Hydrometeorology2691301 to 13131525-755Xhttps://doi.org/10.1175/JHM-D-24-0146.12006281; 2003076National Science Foundation