Table 2.

(a) Evaluation of the period-mean (1 May–30 June 2010) multi-global model free simulations against the CASTNET observations, only at the sites where 95% of the hourly O₃ observations are available. Evaluation of the individual models is summarized in (b). (b) Evaluation of the period-mean (May–June 2010) global model free simulations against the EANET and CASTNET observations. The STEM boundary condition models are highlighted in bold. (c) Evaluation of the period-mean (May–June 2010) multi-global model free simulations against the EANET observations in Japan and South Korea. Evaluation of the individual models is summarized in (b).

(a) Subregion	US EPA regions contained	Number of sites	Mean bias (ppbv)		RMSE (ppbv)
			3 BC* models	8 global models	3 BC models	8 global models
Western US	8, 9, 10	19	−5.68	−2.52	10.37	7.05
Southern US	4, 6	18	11.61	10.24	13.62	11.96
Midwest	5, 7	13	8.03	7.66	9.16	8.67
Northeast	1, 2, 3	17	9.55	10.63	10.28	11.24
All	1–10	67	5.49	6.22	11.11	9.96

(b) Network	Number of sites	RMSE (ppbv)
		CAM- Chem	EMEP	CHASER	SNU–GEOS- Chem	GEOS-Chem adjoint	RAQMS	OsloCTM3 v2	C-IFS
CASTNET	67	13.30	11.61	15.43	15.55	13.48	9.32	11.05	11.00
EANET	11	10.38	9.96	11.39	9.18	11.04	8.60	12.97	10.86

(c) Country	Number of sites	Mean bias (ppbv)		RMSE (ppbv)
		3 BC* models	8 global models	3 BC models	8 global models
Japan	8	0.36	1.01	8.77	9.25
South Korea	3	1.14	3.98	8.37	10.51
All	11	0.57	1.82	8.66	9.61

^*BC: boundary conditions.