Abstract Surface winds, meteorites, industry, and natural disturbances such as volcanoes produce vast quantities of dust that is distributed throughout the atmosphere. Surface winds and natural convection currents also carry micro-organisms such as bacteria, pollen, spores, and soil algae into the atmosphere. There is evidence of concentrations of these micro-organisms at various altitudes indicating biologic stratification due to meteorological conditions. Aerosols of different types found in the lower atmosphere do, under certain circumstances, yield detectable radar echoes. Normal dust and biological aerosol concentrations found in the atmosphere will not yield detectable radar echoes at microwave frequencies but abnormally high concentrations could. The electrical characteristics, physical characteristics, and distribution density of the aerosols are considered in determining their microwave scattering and reflection properties.