Sensitivity of MM5-simulated planetary boundary layer height to soil dataset: comparison of soil and atmospheric effects

The effects of two soil datasets on planetary boundary layer (PBL) height are analyzed, using model simulations. Simulations are performed with the MM5 weather prediction system over the Carpathian Basin, with 6 km horizontal resolution, investigating three summer days, two autumn, and one winter day of similar synoptic conditions. Two soil datasets include that of the United States Department of Agriculture, which is globally used, and a regional Hungarian called Hungarian unsaturated soil database. It is shown that some hydraulic parameter values between the two datasets can differ up to 5-50%. These differences resulted in 10% deviations in the space-time-averaged PBL height (averaged over Hungary and over 12 h in the daytime period). Over smaller areas, these relative deviations could reach 25%. Daytime course changes in the PBL height for reference run conditions were significant (p < 0.01) in a parts per thousand 70% of the grid points covering Hungary. Ensemble runs using different atmospheric parameterizations and soil moisture initialization setups are also performed to analyze the sensitivity under changed conditions. In these cases, the sensitivity test showed that irrespective of the radiation and PBL scheme, the effect of different soil datasets on PBL height is roughly the same. PBL height is also sensitive to field capacity (I similar to(f)) and wilting point (I similar to(w)) changes. I similar to(f) changes seem to be more important for loamy sand, while I similar to(w) changes for the clay soil textural class.