Model Change Bulletin

                                MCB#1                       01/16/2013

                        AERSURFACE (dated 13016)

This Model Change Bulletin documents changes made to the AERSURFACE 
Tool for determining surface characteristics for use in processing 
meteorological data with AERMET, the meteorological processor for the
AERMOD dispersion model.  A brief description of the changes is provided 
below.  Additional details are also available through comments embedded 
in the Fortran source code. Changes to the user instructions associated 
with this update are documented in a revised AERSURFACE User's Guide.

This revised version of AERSURFACE (dated 13016) includes the following
modifications relative to the previous version (dated 08009):

-- Bug Fixes:

   1.  Corrected problems with reading GeoTIFF NLCD files that
       are "tiled", rather than "stripped", as assumed in the 
       original design.  Processing of "tiled" data with version
       08009 could produce erroneous results. Several subroutines
       were added or modified as part of these changes.

   2.  Incorporated a minimum distance from the land cover pixels 
       to the center of the study radius for purposes of applying an
       inverse-distance weighting for estimating surface roughness.  
       Sensitivity of roughness has been found in some cases with the 
       pixel center located very close to the center of the study 
       radius.  The minimum distance is set at 15 meters (one-half 
       the 30m pixel resolution).

   3.  Modified mod_AlbersProj.f to correct projection parameters
       for the state of Washington, used in processing State NLCD
       1992 files in a '.bin' format.

   4.  Modified sub_GetLCCounts.f to correct the calculation of
       the study radius as cells and corrected the calculation
       of study center column and row indexes.  Use of incorrect
       Fortran intrinsic function and mixed-mode computations
       could have resulted in slight errors for these calculations.

-- Enhancements:

   1.  Improved TIFF reader routine (Read_TiffTags) to read all
       TIFF tags and GeoKeys.  Returns all values included in the
       data file, and a separate routine (sub_Proc_TiffTags.cfm) 
       evaluates a subset of tags and GeoKeys required to extract 
       and process land cover data.  Provides greater flexibility 
       to read NLCD data in GeoTIFF format from alternative sources.  
       These enhancements also include more robust error handling
       to avoid processing of GeoTIFF data that do not meet the
       specifications required by AERSURFACE.

   2.  Modified sub_GetUserInput routine to improve error handling
       and reporting in order to minimize runtime errors and to 
       facilitate identifying and correcting input errors associated 
       with use of redirected input files.

-- Miscellaneous:

   1.  Modified surface roughness values for categories derived
       as weighted averages of other categories (Categories 21, 
       23, 43, and 91; Low Int Residential, Comm/Indust/Trans,
       Mixed Forest, and Woody Wetlands) to reflect weighted 
       geometric mean values rather than weighted arithmetic 
       mean values. This change results in better consistency 
       between the method for deriving roughness estimates based 
       on a weighted mix of other categories and the method used 
       to process the roughness values across the domain within 
       AERSURFACE. 

       Category weights used in determining the weighted mean
       values were also adjusted as part of this reassessment of
       derived roughness categories.  The weights assigned for the 
       weighted geometric mean values are more consistent with
       the definitions of the categories used in determining
       the weighted means.

   2.  Updated subroutines UTMGEO and NADCON to be consistent 
       with the updated AERMAP Terrain Processor, dated 09040.
       Subroutine UTMGEO was also moved from aersurface.f to a
       separate file (sub_UTMGEO.f).

   3.  Modified sub_GetLCCounts.f for mixed-mode computations
       involving INTEGER (KIND=8) variables and constants.


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                       *   IMPORTANT   *
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This program will henceforth be identified by its name and a Julian date,
i.e.: AERSURFACE (dated 13016).  Future changes to AERSURFACE will be 
identified by an updated Julian date found at the beginning of the 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.