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Land-surface partitioning of net radiation into sensible and latent heat fluxes is critical for hydroclimatic processes but remains highly uncertain due to limited observations. We show that a suitable extension of the Budyko's curve, a well-known framework in hydrology for water balance estimation, can be utilized effectively to partition the surface energy fluxes by expressing the long-term evaporative fraction (EF) as a function of the dryness index only. The combination of this energy partitioning method with hydrological observations allows us to estimate the surface energy components at watershed and continental scales. Using this new framework, we show that North American Regional Reanalysis data overestimate surface evaporation, likely influencing the modeling of atmospheric convection. The obtained hydrologic constrains on energy partitioning can be used to provide more accurate estimations of surface energy fluxes for hydroclimatic predictions.

Plain Language Summary Evaporative cooling of the Earth's surface water reduces the amount of radiation that goes into sensible heat, namely, the portion of radiation that produces higher temperatures. However, these quantities at regional and global scales remain largely uncertain due to limited observations, likely affecting weather and climate predictions. Here we show that a well-known and efficient framework often used in the hydrological science can be extended to identify the portion of energy used for evaporative cooling at watershed and continental scales, potentially contributing to solve one of the most vexing problems in weather forecast and climate predictions.