Abstract: In certain embodiments, a portable atmospheric monitor comprises a housing at least partially enclosing an inner chamber. The housing comprises an inlet and an aperture. The monitor also includes at least one light sensor arranged within the housing. The light sensor that senses one or more wavelengths of sunlight received via the aperture. The monitor includes at least one light-scattering sensor that senses PM received via the inlet. The monitor includes a processor arranged within the housing and coupled to the at least one light sensor and the at least one light-scattering sensor. The processor is configured to: receive a light signal from the at least one light sensor; receive a PM signal from the at least one light-scattering sensor; determine the aerosol optical depth based upon the light signal; and determine the PM concentration based upon the PM signal.