Patent ID: 8831884

Claim:
A method of determining a size distribution of water droplets in a cloud comprising: sampling a depth of a could with a beam of electromagnetic radiation, the beam of electromagnetic radiation comprising a beam emitted from a laser; measuring a scattering signal of the electromagnetic radiation returned from the cloud over a range of a field of view angles p total (θ) to provide a measured scattering curve; removing a portion of the measured scattering curve; replacing the removed portion with an extrapolation of the remaining measured scattering curve to provide an estimated scattering curve; determining a first estimate droplet size distribution n (1) (D) from the estimated scattering curve using a forward scattering model; providing a calculated scattering curve from n (1) (D) using a direct backscatter model and the forward scattering model; comparing the calculated scattering curve with the measured scattering curve to determine whether the calculated scattering curve follows the measured scattering curve within a set tolerance; determining a first estimate of a droplet median volume diameter (D MVD (1) ) from n (1) (D) and determining a first estimate of a shape parameter (μ (1) ) from n (1) (D); and altering the value of D MVD (1) in response to the calculated scattering curve not following the measured scattering curve within the set tolerance to provide a second estimate of the droplet median volume diameter D MVD (2) , and using D MVD (2) and μ (1) to provide a second estimate droplet size distribution n (2) (D).