Process analysis of a regional air pollution episode over Pearl River Delta Region, China, using the MM5-CMAQ model

Figures & data

Figure 1. Three nested modeling domains for MM5 (solid square frame) and CMAQ (dashed square frame) models. (resolution is 36 km, 12 km, and 4 km, respectively) (b) The 4-km grid MM5 domain pointed with the main cities over Pearl River Delta region.

Figure 2. The emissions of (a) PM₁₀, (b) SO₂, and (c) NO_x in 2004 in Guangdong province calculated by the SMOKE model.

Figure 3. (a) Surface-weather chart in East Asia at 2:00 p.m. on October 11, 2004. (b) The distribution of air pollution index (API) in Guangdong province on October 11, 2004 (I: good; II: fair; III: polluted).

Table 1. Performance statistics of MM5 meteorological predictions during October 10–12, 2004, at Guangzhou station in different horizontal resolution

		MeanObs	MeanMod	r	MB	RMSE	NMB (%)	NME (%)
T2 (°C)	36 km	24.35	23.24	0.98	−1.89	2.07	−7.76	7.76
	12 km	24.35	22.58	0.98	−1.77	2.02	−7.26	7.27
	04 km	24.35	23.24	0.98	−1.11	1.58	−4.56	5.26
RH2 (%)	36 km	53.40	50.12	0.69	−3.28	13.45	−6.13	45.91
	12 km	53.40	50.11	0.70	−3.29	13.37	−6.16	43.37
	04 km	53.40	48.81	0.69	−4.59	13.90	−8.59	38.99
WDR10 (°)	36 km	93.67	78.42	0.92	−15.24	48.96	−16.28	65.57
	12 km	93.67	81.04	0.92	−12.63	47.81	−13.48	67.10
	04 km	93.67	78.07	0.92	−15.59	44.50	−16.65	61.55
WSP10 (m/s)	36 km	1.54	2.07	0.23	0.53	1.34	34.34	21.74
	12 km	1.54	2.14	0.19	0.60	1.43	38.82	20.26
	04 km	1.54	2.08	0.26	0.54	1.32	35.05	20.45

Figure 4. Temporal variations of simulated (by MM5) and observed 2-m temperature (T2), 2-m relative humidity (RH2), 10-m wind direction (WDR10), and 10-m wind speed (WSP10) at Guangzhou city during October 10–12, 2004.

Figure 5. Simulated (by CMAQ) and observed temporal variations of PM_2.5, SO₂, NO, and O₃ at Guangzhou site during October 10–12, 2004.

Table 2. The correlation coefficients between different cities calculated using eq 6

	Group I		Group II				Group III		Group IV
	GZ	FS	DG	SZ	ZS	ZH	JM	ZQ	HZ
GZ	1	0.32	0.26	−0.04	−0.14	0.21	−0.17	0.12	0.19
FS	0.32	1	0.29	0.25	0.14	0.08	−0.13	0.29	−0.08
DG	0.26	0.29	1	0.31	0.54	0.31	0.31	0.45	0.21
SZ	−0.04	0.25	0.31	1	0.61	0.37	0.27	0.32	0.03
ZS	−0.14	0.14	0.54	0.61	1	0.47	0.47	0.21	0.09
ZH	0.21	0.08	0.31	0.37	0.47	1	0.45	0.33	0.13
JM	−0.17	−0.13	0.31	0.27	0.47	0.45	1	0.60	0.01
ZQ	0.12	0.29	0.45	0.32	0.21	0.33	0.60	1	0.19
HZ	0.19	−0.08	0.21	0.03	0.09	0.13	0.01	0.19	1

Note: Group I: GZ, FS. Group II: DG, SZ, ZS, ZH. Group III: JM, ZQ. Group IV: HZ.

Figure 6. Simulated (by MM5) 10-m wind field (black arrows) and vertical velocity at 920 hPa (shaded) over PRD region at 10:00 a.m. on October 11, 2004.

Figure 7. Classification of cities over PRD region. I. Large-emission group. II. The first downwind group. III. The second downwind group. IV. Small-emission group.

Figure 8. Hourly contributions of emissions (EMIS), dry deposition (DDEP), horizontal transport (HORI), and vertical transport (VERT) to the concentration change of PM₁₀, PM_2.5, SO₂, and NO_x predicted by CMAQ at (a) Guangzhou, (b) ZhongShan, (c) JiangMen, and (d) HuiZhou sites during October 10–12, 2004.

Figure 9. Average contributions of (a) emissions (EMIS), (b) dry deposition (DDEP), (c) horizontal transport (HORI), and (d) vertical transport (VERT) to the concentration change of PM₁₀, PM_2.5, SO₂, and NO_x predicted by CMAQ for nine cities over PRD during October 10–12, 2004.