Characterization of the Saturated Condition Potential Evaporation and Evaporative Demand and Their Implications in the Complementary Relationship

Abstract:

The Complementary Relationship (CR) between actual regional scale evaporation (ET) and apparent potential evaporation or evaporative demand (E_o) has elucidated our conceptual understanding of evaporative flux, despite a lack of rigorous proof of the concept. This presentation reviews the concept briefly, and describes significant historical advances, current progress and promising ideas. It covers complementarity, the energy budget, symmetry/asymmetry, scale issues of time and space, selection of regional-saturation-condition apparent potential evaporation (E_po) and E_o , advection, atmospheric boundary layer entrainment, and atmospheric stability. Recent work and findings by the authors regarding the value of the Priestley and Taylor α and its impact on E_po within CR, and of the implications of use of Penman’s evaporation equation versus other representations of E_o on the asymmetry of the CR will be discussed.