I'll talk about some recent numerical and experimental results concerning local fields spatial and spectral dependence near nanometer-structured metal surfaces with the smallest roughness features of about 10 nm irradiated by external light in the spectral region from 400 to 1,000 nm. The local near-zone spectra (spectral dependencies of the intensity of EM field at different points close to the surface) can be very different from the integral spectra observed in the far-zone. In particular, the local spectra exhibit resonances with the linewidths much smaller than that for the integral absorption. The particular shape of a local spectrum depends strongly on the point where it is measured, with a correlation length as small as 100 nm. The other manifestation of this phenomenon is a total change of the spatial distribution of the local field when the external wavelength is changed by an amount comparable to the typical linewidth of a local spectrum resonance; the integral scattering and absorption characteristics almost do not change due to such small change of the external wavelength. I will discuss also the dependence of the spatial distribution of local field on the angle of incidence of the external light, which is a less obvious phase effect.

The numerical calculations for the local fields were carried out in the model of fully retarded dipole-dipole interaction  between small elementary metal "bricks" from which the entire rough surface is built. This approach is equivalent, with some simplifying assumptions, to digitization of the exact Maxwell equations.