<p>The dissimilarity in turbulent transport among physical variables and the role of turbulent coherent structures within the unstable surface layer are investigated via the urban–rural contrasts using one-month observations in Beijing, China. The turbulent transport of heat and momentum is similar under weakly unstable conditions, while the turbulent transport dissimilarity increases as the atmospheric instability strengthens at both sites. This variation is closely linked to the transformation of coherent structures, i.e., mechanically generated structures are replaced by buoyancy-driven ones (e.g., thermal plumes and convective circulations). Meanwhile, the turbulent transport dissimilarity between the heat and passive scalars (i.e., H₂O and CO₂) is regulated by surface characteristics. In homogenized rural areas, the turbulent transport of heat and passive scalars remains similar under unstable conditions. However, in urban areas, passive scalars are transported differently from heat due to the heterogeneous distribution of their respective sources/sinks. Furthermore, it is also found that the transformation of turbulent coherent structures depends on the balance between mechanical and buoyant effects. For example, stronger shear in urban areas delays the formation of thermal plumes, while stronger surface heating enhances their final intensity. Overall, the transformation of coherent structures and the heterogeneity in source/sink distribution govern turbulent transport dissimilarity, for heat-momentum and heat-passive scalar transport, respectively. The results advance our understanding of turbulent transport dissimilarity in the actual atmosphere, which is helpful to improve the parameterization of the boundary-layer in mesoscale weather models.</p>