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This study compares three modifications to the one-dimensional planetary boundary layer scheme that is implemented in the σ–θ hybrid-b version of the Mesoscale Analysis and Prediction System (MAPS) and the Rapid Update Cycle (RUC). All three modifications are based on the incorporation of a simple soil model into the basic version to more accurately calculate the moisture and heat fluxes across the ground surface. The presented schemes are of increasing sophistication: the first model combines the soil model with heat and moisture budget equations for the ground surface and uses an explicit numerical scheme to compute the surface fluxes; the second model uses a more energy-conservative implicit solution for the latent and sensible surface fluxes and heat and moisture soil fluxes; the third model further incorporates a simple parameterization of the evapotranspiration process. The comparison includes the effect of different schemes on diurnal changes of surface temperature and soil heat flux. The schemes are tested for two case studies; a dry case from the O'Neill, Nebraska, Great Plains Turbulence Field Program and a moist case from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment. Tests are performed to evaluate sensitivity to soil parameters related to thermal diffusivity and to vertical resolution of the soil scheme. Overall, the comparison supports the idea that implementation of a multilevel soil model is competitive with and can even improve the ground surface temperature forecast over that produced by the present MAPS implementation of the force restore method. The case study demonstrates that incorporation of a primitive evapotranspiration model can give positive results.
Smirnova et al. (Fri,) studied this question.