Perform a Mie calculation for the size parameter range from 1 to 1000 for a single sphere with a radius of 10 µm. Plot the extinction efficiency as a function of size parameter and describe the result.

Perform another Mie calculation for a gamma size distribution with an effective variance of 0.1 and again plot the extinction efficiency as a function of size parameter. Which differences do you observe compared to the single particle?

In order to obtain the extinction efficiency for a size distribution, the Mie code (src/mie.c) requires a small modification (please contact Claudia!).

Extinction efficiency as a function of size parameter. The blue line is for a single sphere with a radius of 10 micrometers and the green line is for a gamma size distribution with an effective radius of 10 micrometers. For large size parameters the extinction efficiency approaches the geometrical optics limit of 2, which states that the extinction cross section equals 2 times the geometrical cross section.

Asymmetry parameter as a function of size parameter. The blue line is for a single sphere with a radius of 10 micrometers and the green line is for a gamma size distribution with an effective radius of 10 micrometers. For large size parameters the geometrical optics limit of 0.87 is approached. For small size parameters the asymmetry parameter goes towards 0 which corresponds to Rayleigh scattering.

The oszillations (ripple structure and also major maxima and minima) in the results for the single droplet (higher order terms in Mie series) are averaged out when integrating over a size distribution.