Table 6. Summary Statistics for Evaluation of Concentrations of Aerosol Speciesa

Species	Western United States	Eastern United States	United States
	MB, microng m-3	NMB	MB, microng m-3	NMB	MB, microng m-3	NMB
1.37 x [SO42-]	 0.33	 32.4%	 0.90	 21.6%	 0.49	 25.9%
1.29 x [NO3-]	0.35	+75.6%	 0.41	 54.4%	0.14	+25.0%
BC	 0.04	 24.2%	0.09	+28.7%	 0.004	 1.9%
OA	 0.66	 44.8%	 0.31	 14.7%	 0.56	 34.2%
PM2.5	 0.68	 21.8%	 1.38	 18.8%	 0.87	 20.4%

aThe boundary between the western and eastern United States is taken as 95degreesW. Mean bias (MB) = 1/NNsumi=1 (Pi - Oi ), and normalized mean bias (NMB) = 100\% x Nsumi=1 (Pi - Oi)/Nsumi=1 Oi, where Pi is the model prediction at station i, Oi is the observed value at station i, and N is the number of model observed pairs for all valid monitoring data.