In this paper, we give a numerical characterization of nef arithmetic $ℝ$-Cartier divisors of $C^0$-type on an arithmetic surface. Namely an arithmetic $ℝ$-Cartier divisor $\overline{D}$ of $C^0$-type is nef if and only if $\overline{D}$ is pseudo-effective and $\widehat{\mathrm{deg}}\left({\overline{D}}^2\right)=\widehat{\mathrm{vol}}\left(\overline{D}\right)$.