The use of realistic aerosol models to limit the range of aerosol possibilities in deriving aerosol scatter

The lidar equation is given by E(r,λ)= C(λ)σ _s(r,λ)P(180,rλ)T(rλ)²/4πr ² (equation 1). E(r,λ) is the energy received at a distance r, C(λ) is the lidar calibration factor accounting for the laser power and detector efficiency, σ_s(r,λ) is the combined aerosol and molecular scattering coefficient (in m^-1), P(180,r, λ) is the weighted acrosol-molecular phase function at the backscattering angle of 180 degrees, and T² (r,λ) is the two way transmission due to aerosol and molecular extinction. If the aerosol type is known at each distance then the aerosol phase function can be calculated and a forward stepping approach can be implemented to derive the aerosol extinction coefficient at each range. Typically the aerosol type is not known and various methods have been used to constrain Eq. 1. Here we investigate the use of multi-wavelength lidar measurements to derive the aerosol phase function as a function of distance. As aerosol extinction at several wavelengths is not sufficient to constrain the aerosol type for large marine aerosols, we use a set of realistic aerosol models to limit the range of aerosol size distribution possibilities. For this paper we also limit ourselves to clean marine conditions where the aerosols are non-absorbing. The most common lidar wavelengths (from an NdYag laser) include 355, 532, and 1064 nm