Geometric cross sections per masses for various types of aggregates. Constituent monomers are 0.1 μm seized icy spherical particles. The solid line shows the geometric cross section of a compact sphere with the same density as constituent particles. The dotted line and the dashed line show the geometric cross sections of BPCA and BCCA clusters, respectively. For BCCA and BPCA, we used empirical formulae by Minato et al. (2006).