Abstract: The PBL climate characteristics over inhomogeneous underlying surface in North China for summer is studied by using the modified Nickerson’s model. The results indicate that the horizontal inhomogeneity of temperature and humidity over the underlying surface plays an important role in the boundary layer climate under conditions of clear and calm day without synoptic system disturbance. The PBL climatic features are closely related to the local circulation. A phenomenon called inversion of humidity in the PBL over a dry bare soil is ascribed to the joint of the heterogeneous humidity pattern and mesoscale advection over the inhomogeneous underlying surface