Revisiting a Two‐Parameter Budyko Equation With the Complementary Evaporation Principle for Proper Consideration of Surface Energy Balance
Daeha Kim, Jong Ahn Chun
Abstract
Abstract The Budyko framework, widely regarded as a simple and convenient tool to synthesize catchment water balance, is often employed with the atmospheric evaporative potential (E p ) that responds to water availability over a land surface. In this study, we demonstrated how the responsiveness of E p to soil moisture deficiency affects outcomes from a conventional Budyko equation. We combined a two‐parameter Budyko equation with the state‐of‐the‐art complementary relationship (CR) of evaporation (E), and analytically showed that the two‐parameter Budyko equation corrects E p to the wet environment E (E w ) of the CR. Using the Budyko equation combined with the CR, we assessed runoff sensitivity to climatic and land surface changes. Results showed that the CR could become a constraint for calibrating the implicit parameter of the Budyko equation. When compared to the Turc‐Mezentsev equation with E p , the shape parameters of the two‐parameter Budyko equation increased to regenerate an ensemble of global E data sets. Correcting E p to E w via the Budyko equation with CR reduced runoff elasticities to land property changes, suggesting that climatic changes are more important to changes in runoff than a prior sensitivity assessment would suggest. This study also suggests that the two‐parameter Budyko equation isolates the effect of the E p adjustment from the shape parameter, allowing it to more properly account for surface energy availability.