                    Model Change Bulletin              
              
                            MCB#2                               1/8/91

                    STAR  (dated 91008)



      This Model Change Bulletin is formal notification of a correction to the
STAR program.  The updated code is dated 91008 and is further identified by
MCB#2.  This version replaces all previous versions of STAR for regulatory
use.  Future changes to this program will be identified by an updated julian
date found on the first line of the model source code and followed by a
reference to a SCRAM BBS Model Change Bulletin (MCB#n) which will explain the
nature and contents of the changes. All Model Change Bulletins for this
program will always be available for back reference on this BBS.  In the
future, notification of changes (MCBs) to this model will be made in the
SCRAM ALERTS section of this BBS immediately following the LOGON procedure.

      This revision of STAR corrects three errors found in the version of STAR
dated 90193.

1.    The first error allowed a blank entry for cloud cover to be
treated as overcast (10/10 cloud cover) when a legal ceiling entry was
present.  Any blank should cause the data to be treated as "missing".

      To correct this problem, the following two lines of code following the
line labeled 308 are DELETED:

      IF(L-11)307,3399,450
 3399 IF(N-4)450,309,450


and REPLACED by the following three lines of code:

      IF ((L .EQ. 11) .AND. (N .NE. 4)) GO TO 450
      IF (L .EQ. 11) GO TO 309
      GO TO 307


2.    The second error occasionally caused the stability class to be calculated
as one class too unstable when (1) the sky is overcast and (2) the ceiling
height is at least 7000 feet and less then 16000 feet.

      To correct this problem, change the line labeled 100 to read:

  100 CONTINUE

and insert the following two lines of code after the line labeled 106:

 1068 IF (ICA-10) 107, 1069, 1069
 1069 IR = IR-1


3.    The third error sets the variable MMM =O (the letter "oh") instead
of 0 ("zero").

      This problem is corrected by CHANGING the line after the line labeled
47 from:

      MMM=O

to:

      MMM=0


4.    The version number on the third line is changed to 91008 as follows:

C                           STAR (DATED 91008)


      The effects of these changes are normally insignificant.  With respect
to the first change, if cloud cover is missing in a data set, the ceiling
height is normally missing also.  In such a case the missing data will be
handled properly by either version.  The most likely case where the correction
will cause changes is where STAR is reading the cloud cover from one column
when the data were actually placed in another column.  In such a case, the
old version will incorrectly use a small portion of the data, while the
corrected version will correctly reject the entire data set.

      With respect to the second change, a comparison was made between the
corrected and uncorrected versions of STAR on the Pittsburgh data for the last
three months of 1964.  Only five stability values were altered as a result of
the code changes to STAR.  In each case, the stability changed from "D" to "C".
We therefore believe the effect of this change to be insignificant.

      The third change will have no effect if the compiler presets all
variables to zero.  Most compilers, including the one used to prepare STAR.EXE,
do this.

      Note that the code on the BBS has been sequenced numbered.  Each line
number begins with "STR" except for lines which have been altered or added
by this change.  The line numbers for the altered and changed lines begin
with "XXX".

      The source code for this program has been compiled with the
Microsoft 5.0 compiler and tested on an PC AT compatible computer.
 

                       ******************
                       * Important Note *  
                       ******************
   
      New Model Change Bulletins will ONLY be issued when there is a change
to the source code for this program. Changes to test cases and/or any pre and
post processors that are included in the archived file for this program will
be addressed and appropriately identified in an amendment to the program's
latest MCB with notification posted in the SCRAM ALERTS section of the BBS.

