The Importance of Heat Storage for Estimating Lake Evaporation on Different Time Scales: Insights From a Large Shallow Subtropical Lake

Abstract

The change in heat storage (Gc) is an essential component of a lake's energy balance, and its importance for lake evaporation (Ew) has been widely recognized. However, the effect of Gc on Ew exhibits diversity across time dimensions. The controls on Gc and the effects of Gc on Ew estimates at different time scales remain largely unexplored. To address these gaps, we identified the primary controls on Gc at an eddy covariance site in a large shallow lake (Lake Taihu) and quantified the role of Gc in estimating Ew on three (hourly, daily, and monthly) time scales based on two energy balance‐based Ew models. Our results indicate that the diurnal variation of Gc is dominated by net radiation and peaks around noon, while the seasonal variation of Gc is mainly controlled by air temperature and peaks in spring. In contrast, the daily variation of Gc is subjective to a confluence of factors—net radiation, wind speed, and relative humidity—displaying more stochasticity than that on the other two time scales. We also found that the importance of Gc for Ew estimates decreases as the time scale extends. Compared to the two models disregarding Gc, considering the effect of Gc enhances the average Kling‐Gupta efficiency (KGE) values of the two models by 1.33, 0.42, and 0.08 on the three time scales, respectively. Overall, this study highlights the importance of time scales in evaluating the effect of Gc on Ew estimates.