  The morphological asymmetry of leading and following sunspots is a well-known
characteristic of the solar surface. In the context of large-scale evolution of
the surface magnetic field, the asymmetry has been assumed to have only a
negligible effect. Using the surface flux transport model, we show that the
morphological asymmetry of leading and following sunspots has a significant
impact on the evolution of the large-scale magnetic field on the solar surface.
By evaluating the effect of the morphological asymmetry of each bipolar
magnetic region (BMR), we observe that the introduction of the asymmetry in the
BMR model significantly reduces its contribution to the polar magnetic field,
especially for large and high-latitude BMRs. Strongly asymmetric BMRs can even
reverse the regular polar field formation. The surface flux transport
simulations based on the observed sunspot record shows that the introduction of
the morphological asymmetry reduces the root-mean-square difference from the
observed axial dipole strength by 30--40 percent. These results indicate that
the morphological asymmetry of leading and following sunspots has a significant
effect on the solar cycle prediction.
