Model Change Bulletin

                                 MCB#2                          04/13/93

                        PLUVUE II (dated 92243)

This Model Change Bulletin documents the revisions to the Plume Visibility
Model, PLUVUE II.  This model was restructured in order to improve the user
interface requirements, revised to remove several errors in the original
code, and designed to run on a personal computer.  The PLUVUE II visibility
modeling system combines three different algorithms: PLUVUE II, PLUIN2, and
MIETBL into one algorithm called RUNPLUVU.  The user of RUNPLUVU may edit
PLUVUE II input files (PLUIN2 portion of RUNPLUVU), select or create Mie
library files as input to PLUVUE II (MIETBL portion of RUNPLUVU), and run the
PLUVUE II visibility algorithm.  The basic computer requirements for using
RUNPLUVU software include a 80386 or higher processor and at least 1 MB of
RAM, a hard disk with sufficient storage space to handle the executable file,
input data files, and output files (file size will vary depending on
application), and a math coprocessor (80 x 87 chip).  The amount of memory
available on any particular PC will depend on the machine configuration
including the amount of memory used by the operating system, memory used by
any special device drivers, and any utility programs resident in memory.  The
amount of memory needed to actually run the software will be somewhat larger
than 1 MB because additional memory is needed for buffers when the program
opens files.  RUNPLUVU is compiled using Lahey F77L-EM/32 Version 5.0.  This
is the extended memory version for 32-bit computers that runs on 386 or
higher PCs with more than 650K memory.

Technical descriptions for all the components of the RUNPLUVU modeling system
are provided in the "User's Manual for the Plume Visibility Model, PLUVUE II
(Revised)," EPA-454/B-92-008.  This document is written in WordPerfect 5.0 and
can also be downloaded from the BBS.  Section 2.1.7 "Code Modifications,"
pages 6-7, provides a complete description of all the corrections made to the
PLUVUE II model.  These changes reflect technical errors in the original code
that were thought to have existed and now were verified, or other technical
errors discovered as a result of work sponsored by EPA.  All changes made to
the model code are those thought to be consistent with the intent by the model
developer; there are no changes to the theoretical formulations and
assumptions.  No significant changes in model predictions were found in the
case tested.