The size of the liquid or solid particles in the atmosphere usually extends from > 0.01 to < 100 µm in diameter. In the earth's atmosphere the distribution function which describes the number of particles as a function of diameter, mass or surface area of the aerosol can be determined reasonably well with modern instrumentation.
Source:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2205 (https://doi.org/10.1351/pac199062112167)