AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
The Role of Grid Resolution on the Overprediction of Aerosol Nitrate by Chemical Transport Models
Maria Zakoura, SPYROS PANDIS, University of Patras
Abstract Number: 727 Working Group: Aerosols, Clouds, and Climate
Abstract Results from recent studies have shown that particulate nitrate is often over-predicted in the Eastern US. NOx from large coal burning power plants and traffic is the major precursor of the nitrate in this area. This study examines the role of horizontal grid resolution on the prediction of PM2.5 nitrate by the three dimensional chemical transport model PMCAMx.
Four cases were investigated. First, the model was applied over the Eastern United States with a 36 km grid resolution during July 2001 (base case scenario). Then, two-way nested grids (36/12 km, 36/4 km and 36/12/4 km) were used over the same area during the same period. Due to lack of high resolution emissions, the emission inventory was interpolated for the higher resolution simulations. The model predictions were evaluated against daily average PM2.5 measurements taken throughout the Eastern United States by the IMPROVE and STN monitoring networks. Hourly PM2.5 measurements taken during the Pittsburgh Air Quality Study were also available.
The simulation with the telescoping nested grids reproduced better the nitrate measurements. The bias for PM2.5 nitrate decreased by 69% for the STN and 65% for the IMPROVE network, when the resolution increased from 36 km to 4 km. Also, the bias decreased by 92% for Pittsburgh. Similar improvements were seen in other areas of the Eastern United States. These results suggest that at least part of the overprediction is caused by the artificial spreading of point-source emissions and the subsequent changes in the nighttime chemistry of both the power-plant plumes and the background atmosphere.