We are using MERRA-2 data for calculating the dry deposition rate of PM2.5. However the MERRA-2 data consists of several PM2.5 components (black carbon, sea salt, dust etc.). The dry deposition rates for each of these components are further provided in 5 size class bins (0.15 micrometer, 0.25 micrometer, 0.4 micrometer etc.). Has anyone worked with the MERRA-2 data and can they suggest the best way to combine the velocities of the different particle sizes, in a cumulative deposition rate for PM2.5?