PULSE: A Novel Potential Underlying Water Use Efficiency-Based Method for Latent Heat and Surface Energy Imbalance Correction

Abstract

Evapotranspiration (ET) plays a critical role in water and energy budgets over the land surface. Eddy Covariance (EC) is the most widely used technique to measure ET at ecosystem scale, providing insights into land–atmosphere interactions and serving as a benchmark for Earth System Models (ESMs). However, ET measurements at EC flux sites suffer from a fundamental limitation: the persistent issue of surface energy budget non-closure. It is essential to correct EC-measured ET fluxes for energy imbalance, both for improved system understanding and diagnostic benchmarking. Here, we introduce PULSE, a new correction approach based on the concept of potential underlying water use efficiency. We implement the method at >250 flux sites globally, and evaluate its performance using a data-driven framework and an ecosystem conductance model. We also benchmark PULSE against existing energy closure correction methods, including the Bowen ratio-based flux correction method (OFC) and Available Energy-based correction (AEC) method. Our results demonstrate that PULSE not only identifies and corrects ET fluxes for energy imbalance but also produces more physically consistent estimates. PULSE is simple, robust, avoids arbitrary assumptions such as Bowen ratio constancy, and is broadly applicable across diverse EC sites.