Comments on OTAG Model Evaluation

Volume II: Summary and Integration--Otag Model Evaluation

Ozone, sentence one: runs for a suburban and urban site near Nashville revealed... NOTE: Findings based on comparisons for two sites are not meaningful!

Ozone, paragraph two: nine rural sites NOTE: Findings based on comparisons for only nine sites are not meaningful!

Precursors, sentence one Nashville urban site NOTE: One site! Not not meaningful!

Please NOTE that this is a regional model-NOT and urban model. Model is not designed to simulate individual site conditions.

Submitted by Mike Koerber on 2/18/97 RecID: MikeKoerber

Re: Volume II: Summary and Integration--Otag Model Evaluation

The type of analyses done for the three sites near Nashville, Downtown, Youth and Giles Co., are not of the same nature as is normally done for an ozone model performance evaluation. In the usual type of analysis, only ozone data are compared and a large number of sites are necessary to build a robust picture of model performance. The analysis done for the Nashville sites used data for ozone, VOC’s, NOx, NOy, and NOz to diagnostically evaluate the chemical performance of the model. This is definitely a valid analysis, large numbers of sites are not required. The choices of an urban, a suburban and a rural site were intended to examine the chemical performance of the modeling system with a 12 km resolution in these environments. Since many of the modeling results for the OTAG modeling which are included in OTAG’s standard statistics and plots include environments in ranging from urban to rural, we think that it is crucial to develop an understanding of just how good results in these areas may be.

Diagnostic analyses are the means by which model performance can be understood and eventually improved.

The UAM-V model can be used in both regional and urban situations. It has already been used for SIP modeling in Atlanta, for instance. The use of a 12-km grid size, as used in OTAG, is not optimal for estimating ozone concentrations at individual sites - as was shown by the work SAI earlier did comparing the results of 12 vs 4 km grids in three areas. In realization of this, the analysis did not attempt to compare hour by hour, or even day by day concentrations at each site. Instead, the emphasis was on the relationships between the chemical species measured at each site compared to that modeled over the entire episode. By taking this approach, differences between the model and measurements which were due to errors in the direction of transport were minimized.

Submitted by Robert Imhoff on 2/24/97 RecID: RobertImhoff

Volume II: Summary and Integration--Otag Model Evaluation

Note Husar side-by-side movies

Submitted by API API on 2/18/97 RecID: APIAPI

Volume II: Executive Summary--OTAG Model Evaluation

In the last paragraph, insert the word regional between evaluating and control in the second to the last sentence.

Submitted by Jeffrey West on 2/18/97 RecID: JeffreyWest

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