We analyze the diurnal cycle of the 2-m thermodynamic data averaged over the First International Land Surface Climatology Project (ISLSCP) Field Experiment site near Manhattan, Kansas, during 1987, using supporting soil moisture data, surface flux data, rainfall, and cloud information. Conserved variable plots are our primary analysis method. We present a summer mean, stratified into dry and wet days, and the monthly seasonal cycle. Further stratifications indicate the control of soil moisture on the surface evapotranspiration, vegetative conductance, and mean diurnal cycle for the boundary layer. We extract composite data sets for the daytime diurnal cycle over grassland in midsummer as a function of soil moisture and show that these are consistent with a mixed layer model for a rapidly entraining boundary layer. ¿ American Geophysical Union 1995