Axes:cell,bin,tracer

SECTIONAL particle size distribution in single-particle VOLUME v, the size grid of a sectional aerosol model (MOSAIC, MADRID, CMAQ-sectional, ...): NBIN contiguous sections `bin` with the NBIN+1 section edges `bin_nodes`, carried independently in each of NCELL spatial cells `cell` (a column level, a grid box -- whatever the consumer's own cell axis is; rename it at the import edge, e.g.