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VISTAS Grid Resolution Sensitivity. Ralph Morris, Bonyoung Koo and Steven Lau ENVIRON International Corporation Gail Tonnesen, Zion Wang, Chao-Jung Chien University of California at Riverside T.W. Tesche and Dennis McNally Alpine Geophysics National RPO Modeling Meeting Denver, Colorado
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VISTAS Grid Resolution Sensitivity Ralph Morris, Bonyoung Koo and Steven Lau ENVIRON International CorporationGail Tonnesen, Zion Wang, Chao-Jung ChienUniversity of California at RiversideT.W. Tesche and Dennis McNallyAlpine GeophysicsNational RPO Modeling Meeting Denver, Colorado May 24-25, 2004
Grid Resolution Sensitivity • Three VISTAS Phase I Episodes • January 2002 • July 1999 • July 2001 • MM5 PX_ACM(2) • 36 km national RPO grid and 12 km Southeast US VISTAS Grid • Examine Model Performance in VISTAS Southeast US Domain
SO4 IMPROVE36 kmvs. 12 km January 2002 – SO4 July 1999 – SO4
WSO4 NADP36 kmvs. 12 km January 2002 – WSO4 July 1999 – WSO4
July 200136 kmvs.12 km July 2001 – SO4 IMPROVE July 2001 – WSO4 NADP
IMPROVE SO4 Fractional Bias and ErrorCMAQ 36 km and 12 km & CB4 and SAPRC99
IMPROVE NO3 Fractional Bias and ErrorCMAQ 36 km and 12 km & CB4 and SAPRC99
IMPROVE OC Fractional Bias and ErrorCMAQ 36 km and 12 km & CB4 and SAPRC99
Ozone Performance July 1999 EpisodeCMAQ and CAMx at 36 km and 12 km (CB4) CMAQ ozone performance degradation to under-estimation with finer grid CAMx ozone performance similar at 36 km and 12 km
CAMx 36/12/4 km Performance for MRPO June 18 – August 13, 2001 Episode Mean Normalized Bias Degradation in most gas-phase species with higher resolution Aerosol species stay same or improve
CAMx 36/12/4 km Performance for MRPO June 18 – August 13, 2001 Episode Mean Normalized Gross Error
Conclusions: Grid Resolution Sensitivity • Effects of grid resolution on model performance is mixed • Changes in precipitation patterns and magnitudes can have large effect locally • Changes in transport patterns also can have big local effect (e.g., Jim Boylan’s analysis of sulfate clouds) • 12 km grid technically superior for grid modeling than 36 km, but still does not resolve point sources and urban areas very well • 12 km takes more CPU time than 36 km • VISTAS Phase II annual modeling will use both 36 and 12 km grids