Using optimal interpolation to assimilate surface measurements and satellite AOD for ozone and PM_2.5: A case study for July 2011

Figures & data

Table 1. WRF-ARW dynamic and physical options used in this study.

	Schemes	Remarks and reference
Advection	Runge–Kutta 3 advection scheme	Wicker and Skamarock (2002)
Shortwave radiation	Dudhia	Dudhia (1989)
Longwave radiation	RRTM	Mlawer et al. (1997)
PBL turbulent mixing	Yonsei University Scheme	Hong et al. (2006)
Cloud Micro Physics	WRF single-moment, six-class scheme	Hong and Lim (2006)
Surface layer heat/momentum exchange	MM5 Similarity Scheme	Zhang and Anthes (1982)
Land surface exchange	Unified Noah Land Surface Model	Tewari et al. (2004)

Table 2. CMAQ dynamic, physical, and chemical options used in this study.

	Parameterization scheme	Remarks and reference
Advection	Piece-wise parabolic method	Mathur et al. (2005)
PBL turbulent mixing	Asymmetric Convective model2	Pleim (2007)
Cloud convection mixing	Asymmetric Convective model	Mathur et al. (2005)
Surface layer heat/momentum exchange	Monin–Obukhov similarity theory	Monin and Obukhov (1954)
Gas phase chemistry	Carbon Bond Mechanism version 5 with Toluene and Chloride chemistry (cb05tucl)	Sarwar et al. (2011)
Photolytic attenuation by clouds	WRF clear sky flux and cloud fraction	Mathur et al. (2005)
Aerosol size distribution	Trimodal log-normal distribution	Binkowski and Shankar (1995)
Aerosol chemistry	Module Aero5 of CMAQ4.7.1	Binkowski and Shankar (1995)
Dry deposition	M3Dry	Mathur et al. (2005)

Figure 1. Prediction cycles and assimilation diagram.

Table 3. OI-related settings in this study.

Cases ofstudies	Assimilation times	Settings of relative uncertainties
OI1 (7 × 7 OI)	00z, 06Z, 12Z, 18Z for AIRNow data; 18Z for MODIS AOD (±1 hr)	0.6 for modeled aerosols and 0.4 for modeled O3
OI2 (7 × 7 OI)	00Z, 06Z, 12Z, 14Z, 17Z, 19Z for AIRNow; 17Z and 19Z for MODIS (±2 hr)	2.0 for modeled aerosols and 0.4 for modeled O3
OI3 (7 × 7 OI)	00Z, 06Z, 12Z, 14Z for AIRNow; 17Z and 19Z for MODIS (±2 hr)	Dynamic uncertainties up to 5.0 for modeled PM2.5 and up to 0.6 for modeled O3
OI4 (11 × 11 OI)	00Z, 06Z, 12Z, 14Z, 17Z, 19Z for AIRNow; 17Z and 19Z for MODIS (±2 hr)	Dynamic uncertainties up to 10.0 for modeled PM2.5 and up to 1.0 for modeled O3

Table 4. Hourly statistical results over CONUS from 12Z, 07/06/2011 to 12Z, 07/07/2011: Correlation coefficients and mean biases (MB).

Cases ofstudies	O3 (ppbV)	PM2.5 (µg/m^3)
Base case	R = 0.53, MB = 2.54	R = 0.23, MB = –7.14
OI1	R = 0.56, MB = 2.36	R = 0.24, MB = –2.63
OI2	R = 0.58, MB = 1.06	R = 0.39, MB = –1.33
OI3	R = 0.52, MB = 2.08	R = 0.36, MB = –1.89
OI4	R = 0.56, MB = 1.55	R = 0.40, MB = –0.11

Figure 2. Dynamic relative uncertainties for AIRNow OI used in OI4 case at 17 UTC: (a) aerosol and (b) ozone.

Figure 3. Predicted and OI-assimilated surface accumulation-mode sulfate at 17Z, 07/02/2011: (a) the first-guess model (14Z OI4 run), (b) OI4 AIRNow OI only, and (c) OI4 AIRNow+MODIS OI.

Figure 4. Cross-section plot over 39°N of the accumulation-mode sulfate differences: (a) after AIRNow only OI, and (b) after AIRNow+MODIS OI (OI4 run).

Figure 5. Predicted surface PM2.5 and its bias compared to AIRNow measurements in the base case (a) and OI4 (b) over the northeastern United States. The corner color bars show the predicted PM2.5, and the bottom color bars show the biases.

Figure 6. CMAQ base model and 4 OI runs compared to AIRNow surface PM2.5 over continental United States (a) and ozone over northeastern United States (b) (north of 37°N, east of 90°W).

Table 5. Same statistics but for southeastern states (FL, GA, AL, MS, TN, SC, NC, VA, WV) from 12Z, 07/06/2011, to 12Z, 07/07/2011.

Cases ofstudies	O3 (ppbV)	PM2.5 (µg/m^3)
Base case	R = 0.55, MB = 0.22	R = 0.10, MB = –9.90
OI1	R = 0.58, MB = 0.43	R = 0.14, MB = –5.89
OI2	R = 0.61, MB = –0.85	R = 0.22, MB = –3.30
OI3	R = 0.58, MB = –1.40	R = 0.22, MB = –4.50
OI4	R = 0.60, MB = –0.59	R = 0.21, MB = –1.16

Figure 7. Discover-AQ 2011 P-3B flight on July 20: (a) flight path and (b) model/observed ozone comparison.

Figure 8. Discover-AQ P-3B flight on July 27: (a) flight path and (b) model/observed ozone comparison.

Figure 9. The base model (“o” symbol and solid fit line) and OI4 (“+” symbol and dash fit line) O₃ versus observation for 13 Discover-AQ P-3B flights (07/02/2011–07/29/2011) below 2 km.

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