A system for determining visibility, the system comprising: a particle sensor unit (110, 210) configured to be mounted onboard a vehicle, the particle sensor unit comprising: at least one light source configured to transmit a light beam into an external interrogation air region; a set of receive optics configured to provide at least one receive channel, the receive optics configured to collect a scattered portion of the transmitted light beam from at least one particle in the interrogation air region; and an optical detector in communication with the at least one receive channel and configured to receive the collected scattered portion of the transmitted light beam, the optical detector operative to measure a signal intensity from the scattered portion, the signal intensity indicating a particle size of the at least one particle; and a processor unit (130, 230) in operative communication with the particle sensor unit, the processor unit operative to execute instructions stored on a processor readable medium to perform a method for determining visibility, the method comprising: analyzing data received from the particle sensor unit to determine particle distribution in a volume of the air region; performing particle differentiation to determine sizes and types of particles in the particle distribution, by binning particle sizes and particle types per the unit volume, the particle types including spherical particles and aspherical particles; calculating visibility data based on the sizes and types of the particles by determining an extinction coefficient for the spherical particles and an extinction coefficient for the aspherical particles, and calculating a visibility value based on a sum of the extinction coefficients; and outputting the visibility data to one or more onboard systems in the vehicle. a particle sensor unit (110, 210) configured to be mounted onboard a vehicle, the particle sensor unit comprising: at least one light source configured to transmit a light beam into an external interrogation air region; a set of receive optics configured to provide at least one receive channel, the receive optics configured to collect a scattered portion of the transmitted light beam from at least one particle in the interrogation air region; and an optical detector in communication with the at least one receive channel and configured to receive the collected scattered portion of the transmitted light beam, the optical detector operative to measure a signal intensity from the scattered portion, the signal intensity indicating a particle size of the at least one particle; and at least one light source configured to transmit a light beam into an external interrogation air region; a set of receive optics configured to provide at least one receive channel, the receive optics configured to collect a scattered portion of the transmitted light beam from at least one particle in the interrogation air region; and an optical detector in communication with the at least one receive channel and configured to receive the collected scattered portion of the transmitted light beam, the optical detector operative to measure a signal intensity from the scattered portion, the signal intensity indicating a particle size of the at least one particle; and a processor unit (130, 230) in operative communication with the particle sensor unit, the processor unit operative to execute instructions stored on a processor readable medium to perform a method for determining visibility, the method comprising: analyzing data received from the particle sensor unit to determine particle distribution in a volume of the air region; performing particle differentiation to determine sizes and types of particles in the particle distribution, by binning particle sizes and particle types per the unit volume, the particle types including spherical particles and aspherical particles; calculating visibility data based on the sizes and types of the particles by determining an extinction coefficient for the spherical particles and an extinction coefficient for the aspherical particles, and calculating a visibility value based on a sum of the extinction coefficients; and outputting the visibility data to one or more onboard systems in the vehicle. analyzing data received from the particle sensor unit to determine particle distribution in a volume of the air region; performing particle differentiation to determine sizes and types of particles in the particle distribution, by binning particle sizes and particle types per the unit volume, the particle types including spherical particles and aspherical particles; calculating visibility data based on the sizes and types of the particles by determining an extinction coefficient for the spherical particles and an extinction coefficient for the aspherical particles, and calculating a visibility value based on a sum of the extinction coefficients; and outputting the visibility data to one or more onboard systems in the vehicle.