  We investigate the effect of the surface bipolar magnetic regions (BMR) on
the large-scale dynamo distributed in the bulk of the convection zone. The
study employs the nonlinear 3D mean-field dynamo model. We model the emergence
of the BMR on the surface through the nonaxisymmetric magnetic buoyancy effect,
which acts on the large-scale toroidal magnetic field in the upper half of the
convection zone. The nonaxisymmetric magnetic field which results from this
mechanism is shallow. On the surface, the effect of the BMR on the magnetic
field generation is dominant. {However, because of the shallow BMR
distribution, its effect on the global dynamo is less compared to the
convective zone dynamo.} We find that the mean-field $\alpha$ effect, which
acts on the nonaxisymmetric magnetic field of the BMRs, provides the greater
contribution to the dynamo process than the BMR's tilt does. Even so, the
fluctuations of the BMR's tilt lead to the parity braking in the global dynamo.
At the surface the nonaxisymmetric magnetic field, which are generated because
of the BMR's activity, shows a tendency for the bihelical spectrum with the
positive sign for the low $\ell$ modes during the maximum of the magnetic
activity cycle.
