June 9, 1993


MEMORAMDUM

SUBJECT:  Wind Field Development for the Urban Airshed
          Model (UAM)

FROM:     Ellen Baldridge, Computer Specialist
          Model Application Section, SRAB, TSD (MD-14)

TO:       Royan W. Teter, Environmental Engineer
          Air Planning and Development Section, Region VII


     In response to your request the Model Clearinghouse has reviewed your
position regarding three different approaches for the development of
appropriate wind fields for the St. Louis UAM application in support of the
State implementation plan (SIP) attainment demonstration.  All three
methods are consistent with the Environmental Protection Agency guidance,
"Guideline for Regulatory Application of the Urban Airshed Model,
EPA-450/4-91-0013."  Section 3.5.1 recommendations state:

     "The Regional Oxidant Model (ROM)/UAM Interface System should be
     used to derive the UAM gridded wind fields when the UAM domain is
     nested within a ROM domain for concurrent time periods and ROM
     predictions are used to derive the hourly UAM boundary
     conditions.  If it is judged by the Technical Committee (and
     identified in the protocol) that a wind field derived from the
     UAM Diagnostic Wind Model (DWM) is more representative of the
     domain-scale flow, then this wind field may be used in lieu of
     the ROM diagnostic wind field.  To minimize mass inconsistency
     problems, the ROM gridded winds may be used as the initial wind
     field in the DWM when generating the UAM gridded wind field."

     Your proposal of developing the method or combination of methods that
produce the most representative wind fields is consistent with the
guidance.  We concur with your request to amend the St. Louis photochemical
modeling protocol.  It is strongly recommended that you obtain sufficient
documentation of the method derived for interfacing the ROM gridded wind
field to the DWM.  The methodology used and the results should be
thoroughly documented for your review of the SIP attainment demonstration.

     If you have any questions, please contact me at (919) 541-5684.

Attachment

cc:  D. Grano, MD-15
     T. Helms, MD-15
     N. Meyer, MD-14
     R. Scheffe, MD-14
     J. Tikvart, MD-14
     D. Wilson, MD-14