Impact of Biogenic Emission Uncertainties on the Simulated Response of Ozone and Fine Particulate Matter to Anthropogenic Emission Reductions

Figures & data

Figure 1. Maps of May-to-September 2002 total biogenic emissions for MEGAN and BEIS: (a) isoprene MEGAN, (b) isoprene BEIS, (c) monoterpenes MEGAN, (d) monoterpenes BEIS, (e) sesquiterpenes MEGAN, (f) sesquiterpenes BEIS, (g) NO MEGAN, and (h) NO BEIS. NO emissions are expressed in Mmols; all others are expressed in Mmols carbon.

Figure 2. Time series of domain total biogenic emissions for MEGAN and BEIS for May to September 2002 for (a) isoprene, (b) monoterpenes, (c) sesquiterpenes, and (d) NO. NO emissions are expressed in Mmols; all others are expressed in Mmols carbon.

Table 1. Summary of anthropogenic and total emissions

	NOx BASE (Mmols)	NOx CTRL (Mmols)	Percent Change	VOC BASE (Mmols carbon)	VOC CTRL (Mmols carbon)	Percent Change	CO BASE (Mmols carbon)	CO CTRL (Mmols carbon)	Percent Change
Anthropogenic	98,285	38,485	−61	224,002	186,238	−17	686,845	563,740	−18
Biogenic MEGAN	2,524	2,524	NA	1,162,052	1,162,052	NA	66,705	66,705	NA
Biogenic BEIS	6,136	6,136	NA	624,709	624,709	NA	53,606	53,606	NA
Total MEGAN	100,809	41,008	−59	1,386,054	1,348,290	−3	752,920	629,815	−16
Total BEIS	104,421	44,620	−57	848,711	810,947	−4	740,451	617,346	−17
Notes: CO=carbonmonoxide,NA=notapplicable.

Table 2. List of model simulations analyzed in this study

Simulation Name	Anthropogenic Emissions	Biogenic Emissions
BASE-MEGAN	∼2005	MEGAN version 2.04
BASE-BEIS	∼2005	BEIS version 3.14
CTRL-MEGAN	Projected 2012 emissions with an additional across-the-board reduction of 40% in anthropogenic NOx emissions	MEGAN version 2.04
CTRL-BEIS	Projected 2012 emissions with an additional across-the-board reduction of 40% in anthropogenic NOx emissions	BEIS version 3.14

Figure 3. (a) Boxplots illustrating the diurnal distributions of observed and BASE-MEGAN simulated hourly isoprene concentrations. For each hour of the day, the boxes represent the range between the 25th and 75th percentile of all concentration values for that hour across the May 15 to September 30 analysis period and the 29 hourly isoprene monitors in the modeling domain, whereas lines indicate the median values. (b) Same as in panel a but for observations and BASE-BEIS.

Table 3. Model performance statistics for DM8H ozone concentrations across 601 monitors for May 15 to September 30, 2002

	Mean Observed (ppb)	Mean Models (ppb)	Mean Bias (ppb)	Normalized Mean Bias (%)	Mean Error (ppb)	Normalized Mean Error (%)	Correlation Coefficient
BASE-BEIS	55.4	53.9	−1.5	−2.7	9.1	16.5	0.79
BASE-MEGAN	55.4	57.3	+1.9	+3.65	9.6	17.4	0.78

Figure 4. Maps of seasonal average DM8A ozone concentrations from the four model simulations and their differences: (a) BASE-MEGAN, (b) CTRL-MEGAN, (c) BASE-BEIS, (d) CTRL-BEIS, (e) BASE-MEGAN minus BASE-BEIS, and (f) CTRL-MEGAN minus CTRL-BEIS. All concentrations were averaged for May 15 to September 30, 2002 and are shown in ppb.

Figure 5. Maps of the H₂O₂/HNO₃ indicator ratio for the four model simulations. (a) BASE-MEGAN, (b) BASE-BEIS, (c) CTRL-MEGAN, and (d), CTRL-BEIS. The indicator ratio was computed from average 12:00 to 5:00 p.m. concentrations for May 15 to September 30, 2002.

Figure 6. Maps of the dimensionless RRF for DM8A ozone calculated for the MEGAN and BEIS platforms using the BASE and CTRL emission scenarios: (a) RRF for the MEGAN platform, (b) RRF for the BEIS platform, and (c) RRF for the MEGAN platform minus RRF for the BEIS platform. Areas in white represent grid cells for which no RRF could be computed because the minimum selection criteria specified in the guidance document34 were not satisfied.

Table 4. Summary of results from previous studies investigating the impacts of changes in various components of the overall modeling system on estimates of RRFs for DM8H ozone

Study	Factors Considered	Typical Effect on RRF
Sistla et al.48	Photochemical model	≤0.04
	Emissions processor
Jones et al.47	Meteorological model	≤0.04
	Chemical mechanism
Hogrefe et al.44	Photochemical model	≤0.03
	Vertical mixing scheme
Koo et al.53	Updated natural emissions	≤0.04 (Estimated from Figure 7d, which reports percentage changes in average modeled seasonal fourth-highest DM8H ozone)
Kim et al.59	Physics parameterizations in MM5 Grid resolution	≤0.03
Study presented here	Biogenic emissions	0.06 (see Figure 6)

Figure 7. Seasonal average concentrations of various biogenic SOA components for BASE-MEGAN, BASE-BEIS, CTRL-MEGAN, and CTRL-BEIS as well as the differences between the MEGAN and BEIS simulations for the BASE and CTRL emission scenarios. For these bar charts, the concentrations were averaged over all nonwater grid cells. This figure presents the concentrations from the five pathways for the formation of biogenic SOA in CMAQ version 4.7 as described in Napelenok et al.,56 Foley et al.,48 and Carlton et al.57; namely, the 2-product formation pathway from ISOP1, the acid-catalyzed formation from ISOP2, the formation pathways from the oxidation of MONO and SESQ, and the oligomerization of aged particles from all OLIG.

Figure 8. Maps of seasonal average biogenic SOA concentrations from the four model simulations and their differences: (a) BASE-MEGAN, (b) CTRL-MEGAN, (c) BASE-BEIS, (d) CTRL-BEIS, (e) BASE-MEGAN minus BASE-BEIS, and (f) CTRL-MEGAN minus CTRL-BEIS. All concentrations were averaged for May 15 to September 30, 2002 and are shown in units of μg/m³.

Figure 9. Maps of seasonal average total organic aerosol concentrations from the four model simulations and their differences: (a) BASE-MEGAN, (b) CTRL-MEGAN, (c) BASE-BEIS, (d) CTRL-BEIS, (e) BASE-MEGAN minus BASE-BEIS, and (f) CTRL-MEGAN minus CTRL-BEIS. All concentrations were averaged for May 15 to September 30, 2002 and are shown in units of μg/m³.

Figure 10. Maps of the dimensionless RRF for May-to-September average total organic aerosol mass and sulfate (SO₄) concentrations calculated for the MEGAN and BEIS platforms using the BASE and CTRL emission scenarios: (a) OM RRF for the MEGAN platform, (b) SO₄ RRF for the MEGAN platform, (c) OM RRF for the BEIS platform, (d) SO₄ RRF for the BEIS platform, (e) OM RRF for the MEGAN platform minus OM RRF for the BEIS platform, and (f) SO₄ RRF for the MEGAN platform minus SO₄ RRF for the BEIS platform.

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