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Dear Colleagues,

We are pleased to announce the release of the latest version of the
CCM Column Radiation Model (CRM). CRM version 2.1 is available via
the CRM homepage at URL http://www.cgd.ucar.edu/cms/crm. This is 
a maintenance release with improved diagnostics but with no new
physics. Answers are do not change so upgrading is not necessary.   
Users of Solaris f90 and f77 are advised not to upgrade (see below).

The CRM is a standalone version of the column radiation code employed
by the NCAR Community Climate Model (CCM3).  Thus the CRM is a
physical process model which isolates the energetics of radiative
transfer from the rest of the CCM3.  The CRM is built from the
radiation routines from CCM3, along with a simple text interface for
the user to input information needed by the radiation calculation.

The CRM uses a two-tier naming scheme which includes both the CRM
version and the version of the CCM code with which it is bundled.  The
current distribution, crm-2.1-ccm-3.6, is CRM version 2.1 which is
built on top of CCM version 3.6.  CRM version 2.x allows the user to take
advantage of the more comprehensive trace gas, paleoclimate, and
aerosol features of the latest CCM. In addition, the text and netCDF
output files contain many more flux, albedo, and optical depth
diagnostics. CRM version 2.1 outputs vertical and spectral profiles
of most fields.

A more detailed list of the changes and improvements to the CRM
follows. Visit the CRM homepage at http://www.cgd.ucar.edu/cms/crm for
complete information.

Sincerely,
Charlie Zender

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User-visible changes from CRM 2.0.2 to CRM 2.1
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1. Improved build procedure

2. Many more diagnostic fields output to text file and to netCDF file

3. Default build assumes Fortran90 compiler with auto-promotion ability.
As a result, building with Solaris f90 is problematic (netCDF file is garbage). 
Building with Solaris f77 is possible, but not with all diagnostic fields.
See CRM homepage and INSTALL file for details.

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User-visible changes from CRM 2.0 to CRM 2.0.2
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1. Improved documentation and FAQ

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User-visible changes from CRM 1.16 to CRM 2.0
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1. Input files for CRM 2.0 are backward-compatible with previous versions
of CRM. Note, however that the meaning of the four albedo fields has
changed slightly.

2. Source directory structure mimics CCM structure

3. Eight new input parameters:
N2O volume mixing ratio
CH4 volume mixing ratio
CFC11 volume mixing ratio
CFC12 volume mixing ratio
Aerosol visible extinction optical depth
Solar constant
Year AD
Longitude

4. CRM now requires netCDF, and must be compiled for IEEE double
precision execution (internal representation as real*8).  

5. Easy to configure band for extra diagnostics. 
   Extra diagnostics will be output for the so-called "visible band".
   By default, this is set to SW band 8 (0.3500--0.6400 um).
   Simply edit the `bnd_idx_vsb' parameter in crmsrb.h to change bands.

6. Easy to configure boundary between visible and NIR spectral regions.
   For diagnostic purposes only, the partitioning between visible and
   NIR regions may be set by altering the parameter `wvl_vsb_NIR_bnd'
   in crmsrb.h. By default, the boundary is set to 0.7 um. 

7. New output diagnostics in both text and netCDF files include:
   Column paths of H2O and O3 (also in Dobson Units)
   Column extinction optical depths
   Visible spectral fluxes
   Solar TOA radiation budget (including albedo ratios)
   Solar surface radiation budget (including direct/diffuse ratios)