COP package description

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mhess
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COP package description

There are two kinds of data files. The first one contains the phasefunctions and the parts of the phasefunctions polarized parallel and perpendicularto the scattering plane. The second one contains tables of the most importantoptical properties in dependence of wavelength and particle size and shape.

  1. COP contains phasefunctions of 6 hexagonal plates in the size range between 20 µm and 2000 µm and of 8 columns between2 µm and 2000 µm. The particles are oriented randomly inspace. There are calculations for 31 wavelengths from 0.28 µmto 10. µm and the data are stored correspondingly in 31 files named for example "0355_R"with 0355 meaning a wavelength of 0.355 µm and "R" representing randomly oriented particles (0001 represents the 10.µm wavelength). Each file contains the phasefunctions of all 14 icecrystals. These phase functions are normalized to 1.="ftp:>
  2. Additionally 7 tables with extinction coefficients, single scattering albedo, asymmetry parameter, and lidarratio of the backscattered signalfor 6 wavelengths and horizontally oriented ice crystals are provided.The corresponding file names are for example "COPTAB15"for a solar elevation angle of 15 degrees. "COPTABR"contains the values for randomly oriented particles.

In these files the particle sizes A and C are given in [µm], the extinction coefficients in [µm*µm] (i.e. as extinction crosssections) and the lidarratio in [sr].


As an example, you may have a look at the

for particles randomly oriented in space, and at

for particles oriented in a horizontal plane.

In addition, there is a


2. PROGRAM

There is a program "COP.FOR", written in standard FORTRAN77(hopefully), to allow the calculation of 'Cirrus Optical Properties', i.e.,size distribution wheighted phasefunctions and other optical properties from the optical properties of the single particles. The program asks for all the input it needs. First you have to select a wavelength. Second you must decide which size distribution you want to use. There are three possibilities:

  1. you may use predefined size distributions after Heymsfield and Platt(1984) (J. Atm. Sci., 41, 846-855). If you decide to do so, you are askedto choose one of the 8 possibilities, corresponding to 8 different temperature ranges.
  2. you may interactively introduce own values of number densities for the indicated radius intervals.
  3. you may write your number densities (in particles / m**3) to the file"NUMIN" from which the program will read them. An example of NUMIN is provided.

After this you have to choose a mixing ratio of columnar and platelike crystals. The program will write its results to the file "RESULTS".Note that the extinction coefficients now are volume extinction coefficients given in [1/m] and are valid for 1 [particle/cm**3]. To get the total value, you have to multiply this with the actual particle number density which is also given.