Diurnal cycles of evaporation using a two-layer hydrological model

The objective of this paper is to study the variation of evaporation in time and space. A two-layer model for solving energy and water balance is presented. The vertical soil column between the soil surface and the water table is divided into the root zone and the transmission zone. The variable infiltration capacity (VIC) concept is used to introduce a spatially varied distribution of soil moisture in the root zone layer. The soil moisture is distributed uniformly in space in the transmission zone layer. The model is used to simulate the fluxes for the King's Creek catchment in Manhattan, Kansas for a period between June through October 1987 (for the four intensive field campaigns), during which the first ISLSCP (International Satelite Land Surface Climatology Project) field experiment (FIFE) was conducted. The model is calibrated using the observed data during the first intensive field campaign (IFC) and validated over the next three IFCS. The energy and water balance equations are solved to vield the time series of fluxes which are compared to their observed counterparts. The model predicted diurnal variation of the evaporative fluxes and the variation of the fluxes after rainfall events is compared with the observations. The model computed fluxes match fairly well with the observed fluxes.