Revisiting the hysteresis effect in surface energy budgets

The hysteresis effect in diurnal cycles of net radiation R_n and ground heat flux G₀ has been observed in many studies, while the governing mechanism remains vague. In this study, we link the phenomenology of hysteresis loops to the wave phase difference between the diurnal evolutions of various terms in the surface energy balance. R_n and G₀ are parameterized with the incoming solar radiation and the surface temperature as two control parameters of the surface energy partitioning. The theoretical analysis shows that the vertical water flux W and the scaled ratio As*/AT* (net shortwave radiation to outgoing longwave radiation) play crucial roles in shaping hysteresis loops of R_n and G ₀. Comparisons to field measurements indicate that hysteresis loops for different land covers can be well captured by the theoretical model, which is also consistent with Camuffo-Bernadi formula. This study provides insight into the surface partitioning and temporal evolution of the energy budget at the land surface. Key Points We physically characterize the hysteresis effect between Rn and G0Wave phase evolution dictates the pattern of hysteresis loopsModel predictions are consistent with field measurements and empirical models