IMPROVE Discussion Forum

From: Bret Schichtel
Date: 1/25/2002
Time: 11:09:34 AM
Remote Name: 129.82.108.32

Frank, You are correct, we did not plot the nitrate variables due to the potential bias. We do not know when we will have this issue resolve and be able to report the ammonium nitrate trends. However, the raw NO3- data are available from the IMPROVE database, so you could explore the trends in these data yourself, keeping the bias issue in mind. <P> The nitrate component is include in the reconstructed PM2.5 and light extinction. This was done by generating constant group 10, 50 and 90 ammonium nitrate values from the 1997-99 data following the procedures from the Draft Guidance for Tracking Progress Under the Regional Haze Rule (9/27/01). These constant values were then used in all years. This procedure eliminates the influence of the nitrate bias, but also eliminates the influence of actual trends in the nitrate data on the light extinction.