On the Complementary Theory to Estimate Actual Evapotranspiration over Grass and Forest with Different Temporal Scales

Evapotranspiration (ET) and rainfall infiltration are important water exchanges between land and atmosphere. Variations of ET and infiltrations are affected by both micrometeorology and wetness and dryness of surface conditions. Groundwater budget is conceptually dominated by ET and infiltration by root uptaking and downward moving of soil water, respectively. Interestingly, how fast or delayed responses of groundwater levels to these fluxes during event or seasonal scales and their interconnected mechanisms are furthermore complicated. Based on previous two years of studies, we proposed two-year of proposal to investigate applicability of complementary theory on estimating grassland and forest ET with different spatial scales. Over the grassland environments, losses of soil moistures will be used to estimate actual ET, pan evaporation will be used to represent potential ET, equilibrium ET will be estimated by the Priestley and Taylor equation. Over the forest environment, the eddy covariance latent fluxes will be sued to estimate actual ET, the Penman type equation will be used to estimate potential ET, and the Priestley and Taylor equation will be used to estimate equilibrium ET. Other tasks like water balance analysis on ET and rainfall infiltration and varied saturated subsurface simulations will be continued as we did for the previous projects for the grassland environment. For the forest environment, we will conduct land process simulations with filed observations for verification. The research will provide contributions to understand dynamic nexus of ET, infiltration, soil moisture and groundwater from event to seasonal scales. Novel scientific knowledge and solution tools of handling interactions among atmospheric water, surface water, soil water, and groundwater will be delivered to facilitate simulations of land surface process and watershed hydrology.