Model Change Bulletin

                                MCB#2                       01/26/2007

                        AERMOD (dated 07026)

This Model Change Bulletin documents changes made to the AERMOD 
Dispersion Model.  A brief description of the changes is provided 
below.  Additional details are also available in the Fortran source 
code.  There are no changes to the user instructions for AERMOD
associated with this update.


   This revised version of AERMOD (dated 07026) includes the following            
   modifications relative to the previous version (dated 06341):
                                                                        
   Bug Fixes:                                                           

   1.  Corrected array indexing problem for POINT, POINTCAP, and
       POINTHOR sources in subroutine SOPARM that could result 
       in incorrect processing of SRCPARAM data for some sources 
       and/or incorrect issuance of fatal runtime errors for number 
       of parameters specified (error code 'E201').

   2.  Modified subroutine SRCQA to include QA checks on the
       number of emission factors input for MHRDOW and MHRDOW7
       options.

   3.  Modified subroutines SRCSIZ and PRESOINC to correct
       potential problem with assignment of array size for
       MHRDOW option.

   4.  Modified subroutine SRCQA to use DOUBLE PRECISION in the
       calculation of area and centroid coordinates for AREAPOLY
       sources. This change avoids problems encountered with
       the Compaq Visual Fortran compiler producing erroneous
       results for some compiler options.

   5.  Modified subroutine MEREAD to assign non-array logical
       variables STABLE and UNSTAB for use in subroutine COMPTG
       for EVENT processing mode.

   6.  Modified subroutines PCALC, VCALC, ACALC and OCALC to
       include calls to subroutine HEFF prior to calculation of
       zsubp for deposition applications.

   7.  Modified subroutine HRQEXT to correct processing of point
       sources under the HOUREMIS option to assign the hourly 
       emission rate, exit velocity, and exit temperature to 0.0 
       if any of these parameters are missing, in conformance with 
       Section 3.3.9 of the AERMOD User's Guide.

   8.  Modified subroutine VDP to prevent potential zero-divide
       condition for cases with zero specific humidity deficit.
       
   9.  Modified subroutines VARINI and RESINI to check for 
       allocation status of allocatable arrays during array 
       initializations.

   Miscellaneous:

   1.  Included additional error-checking for the non-DFAULT,
       BETA-test PSDCREDIT option.

   2.  Modified subroutine PRTSRC to correct format for printing
       QFLAG from A6 to A7 to accommodate SHRDOW7 and MHRDOW7,
       and other minor adjustments to formatting.
       
   3.  Modified code to read the header record of the surface file
       in subroutines MEOPEN, METEXT, and MEREAD to include a 
       separate test on the AERMET version date field under the 
       SCREEN option, to allow for the future use of screening 
       meteorology that is not directly linked to a specific
       version of the AERMET processor.  Also modified subroutine
       METDAT to include meteorological data version date in the
       summary of met data inputs.
       
       
       
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This program will henceforth be identified by its name and a Julian date,
i.e.: AERMOD (dated 07026).  Future changes to this model will be identified
by an updated Julian date found at the beginning of the model source code
and followed by a reference to a SCRAM Model Change Bulletin (MCB#n)
which will explain the nature and content of the changes.  All Model Change
Bulletins for this program will always be available for back reference on
this website.  In the future, notification of changes (MCBs) to this program
will be made in the SCRAM ALERTS section of this website.