MIE TABLE GENERATION FOR RTTOV-SCATT   

12-Mar-2010

Introduction
------------

The Mie tables for use with RTTOV10 RTTOVSCATT can be generated by running 
the script "mie_table_generation.ksh" from the directory containing
the mie table generation software (src/mw_scatt_coef) . All configuration 
and input is specified in the file "channels.dat", which should be in the 
same directory. This enables you to configure:

a) The output directory for the Mie files (which are very large, i.e. 50MB - 200MB each)
b) Instruments, frequencies and hydrometeor types for which to generate Mie parameters
c) Some aspects of the microphysical details of the computation

There are three example files included in this distribution. Rename them to "channels.dat"
in order to use them. 

channels.dat_all   - Will generate Mie tables for all known instruments, including
                     some for which no clear-sky RTTOV coefficients are available.
channels.dat_amsua - Generates just the Mie table for AMSU-A
channels.dat_debug - Does computations for just a single frequency, to enable rapid
                     debug. By default, "channels.dat" is a copy of this

Running the code for the first time
-----------------------------------

The Mie computations are demanding and may take several hours on a single-threaded
platform. Ideally they should be run with 64 threads on a supercomputer, with which
configuration all tables can be created in about 3 minutes.

The following steps are needed:

1) Build RTTOV in the usual way. This will create an executable called 
   "rttov_scatt_make_coef.exe"

2) Copy one of the pro-forma "channels.dat_*" files to "channels.dat" in this
   directory. On installation, "channels.dat" is already present, which is the same as 
   "channels.dat_debug". Use this to get the code up and running.

3) Specify an output directory in channels.dat. It is not recommended to use the
   standard RTTOV coefficients directory, because the newly create Mie tables 
   will overwrite the old. 

4a) In a single threaded environment, just run the script: 

./mie_table_generation.ksh

4b) In a supercomputer environment, submit it to your job-scheduling software 
   .e.g on the ECMWF IBM supercomputer:

llsubmit ./mie_table_generation.ksh


References
----------

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 Ice Hydrometeor Microphysical Assumptions in Radiative Transfer Models at AMSU-B Frequencies. 

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