Read volume fractions from a data file.

Parameters

[in,out]	file	Spec file to read mass fractions from.
[in]	aero_data	Aero_data data.
[in,out]	vol_frac	Aerosol species volume fractions.
[in,out]	vol_frac_std	Aerosol species volume fraction standard deviations.

An aerosol mass fractions file must consist of one line per aerosol species, with each line having the species name followed by the species mass fraction in each aerosol particle. The valid species names are those specfied by the Input File Format: Aerosol Material Data file, but not all species have to be listed. Any missing species will have proportions of zero. If the proportions do not sum to 1 then they will be normalized before use. For example, a mass fractions file file could contain:

 # species   proportion
 OC          0.3
 BC          0.7

indicating that the particles are 30% organic carbon and 70% black carbon.

Optionally, the standard deviation can also be provided for each species as a second number on each line. For example,

 # species   proportion std_dev
 OC          0.3        0.1
 BC          0.7        0.2

indicates that the particles are on average 30% OC and 70% BC, but may vary to have particles with 20% OC and 80% BC, or 40% OC and 60% BC, for example. The standard deviations will be normalized by the sum of the proportions.

Either all species in a given file must have standard deviations or none of them can.