if cfg['TOPO'].getboolean('topoAdd'):
            zv = zv + cExtent*c0*(1. - np.sqrt(np.abs(1. - (np.square(yv) / (cExtent**2)))))*mask
            mask = np.zeros(np.shape(yv))
            mask[np.where(abs(yv) >= cExtent)] = 1
            zv = zv + cExtent*c0*mask