November 7, 1991


MEMORANDUM

SUBJECT:  Phelps Dodge--Hidalgo Modeling Protocol

FROM:     Dean A. Wilson, Meteorologist
          Source Receptor Analysis Branch (MD-14)

TO:       James W. Yarbrough, Air Modeling Contact
          Region VI (6A-AP)


     In response to your request, the Model Clearinghouse has
reviewed:  1) your position with respect to the Industrial Source
Complex Model Short Term (ISCST) equivalency demonstration, and
2) Section 5.0 of the preliminary draft protocol, dealing with
the performance methodology for testing the competing models.

     With respect to the modification to ISCST to accommodate the
input of hourly emissions, we agree with you that an equivalency
demonstration is needed rather than a full performance
evaluation, since the code modifications are not intended to
produce substantive changes in the model estimates.  We have
previously discussed the proposed equivalency test scheme with
you and have agreed that it is appropriate.  Our only additional
suggestion is that, while not critical, it might enhance the
credibility somewhat if the meteorological data used in the test
could come from the same sensor that will be used in the
performance evaluation of competing models.

     With respect to comments on Section 5.0 of the protocol,
Bill Cox has previously reviewed that material.  His comments are
attached.

     If you have any questions, please contact me at 629-5683 or
Bill Cox at 629-5563, as appropriate.

Attachment

cc:  W. Cox