This set of routines computes cloud or aerosol scattering,  absorption,  extinction,  
and backscatter.  The routine uses Mie theory and therefore assumes spherical
particles.  The routine requires the following inputs:  1) a lognormal particle size
distribution,  2) the incident wavelength,  and 3) the particle refractive index.  
The lognormal size distribution can have 1 or 2 modes.  

You will need the 4 routines below:

main subroutine

subroutine 1

subroutine 2

subroutine 3

Here is an example of how to use the main routine ("").  Let's calculate extinction
for a noctilucent cloud (NLC).  You can treat any particle type by using the appropriate
refractive index and size distribution.

The example IDL code:

;- set up some wavelengths to use

   wav = [3.,4.,5.,6.,7.,8.,9.]  ; microns
   nwl  = n_elements(wav)

;- get the refractive indices

   index = complexarr(nwl)

   for j = 0,nwl-1 do begin

     index(j) = index_ice_163K(wav(j))         ; is available on the main software page


;- define a unimodal lognormal NLC size distribution

   n1 = 82. & r1 = 0.051 & s1 = 1.42 & n2 = 0.0 & r2=0. & s2=0.

;- now call partl to compute the extinctions....

   partl, n1,r1,s1,n2,r2,s2,50,wav,index,ext,sca,abc,bac,vol,sfc  

;- see what we got,  ext is the extinction in 1/km and an array of nwl elements