Evaporation from the soil largely determines water availability in terrestrial ecosystems and the partitioning of solar radiation between sensible and latent heat. It is key to hydrology and climate. The evaporation process is complex, involving movement and phase change of water, varying with depth and time. Following water inputs, evaporation occurs at the soil surface, controlled by atmospheric demand. As surface soil water is depleted, evaporation becomes soillimited and shifts below the surface; nonetheless it is generally viewed as a strictly surface process.