Southward redistribution of emissions dominates the 1980 to 2010 tropospheric ozone change Yuqiang Zhang1, Owen R, Cooper2,3, J. Jason West1 1Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, 2Cooperative Institute for Research in Environmenztal Sciences, University of Colorado, 3Chemical Sciences Division, NOAA Earth System Research Laboratory 01/06/2016 AQAST 10, Jan 5th-7th Title Carolina First Steering Committee October 9, 2010

Global ozone precursors shifting southwards Anthropogenic NOx emissions (including biomass burning) from ACCMIP and RCP8.5. 1950 1990 2000 2010 1980 1970 1960 Ozone precursors are increasing globally from 1980 to 2010. CO & NMVOCs increases at south of 30˚N, but decreases north of this latitude from 1980 to 2010. NOx increase south of 40˚N, but decreases north. The peak emission regions shifts southwards. Global anthropogenic NOx increased 21% 1980—2010. Southward shift also seen for anthropogenic CO (6.4% ↑) and NMVOC (6.1% ↑) emissions.

Global tropospheric O3 burden much more sensitive to emission from the tropics and SH Briefly describe this study: what is this study about. What is missing from previous studies. Simulations of 10% NOx reductions from 10 world regions (West et al., 2009). No previous study has separated the influence of emission shifting southwards.

Objectives the spatial distribution of ozone precursor emissions Separate the changes in the global tropospheric ozone burden (BO3) from 1980 to 2010 into contributions from changes in : the spatial distribution of ozone precursor emissions the global magnitude of emissions, and the global CH4 mixing ratio All kinds of global and regional emission inventories have shown that Studies

Methods Global CTM: CAM-chem (Lamarque, 2012) Anthropogenic and biomass burning emissions are from ACCMIP for 1980 and IPCC AR5 RCP8.5 for 2010 (Lamarque, 2010; Riahi, 2011). Biogenic emissions are calculated on-line using MEGAN-v2.1 (Guenther, 2012) Global meteorology are from NASA GEOS-5 meteorology for 2008-2012. Simulations carried out for this study   Emission total in year Spatial pattern in year CH4 concentration S_2010 2010 1798 ppb S_1980 1980 1567 ppb S_Distribution S_Magnitude S_CH4 All the models are run for consecutive five years and we use four years average for the data analysis. We apply the same meteorology for all the simulations, neglecting the effects of climate change or variability. Explain the three sensitivity scenarios.

Tropospheric O3 burden change from 1980 to 2010 1. Global BO3 have increased by 28.12 Tg from 1980 to 2010, with NH accounting for 57%. 2. slightly greater than the combined influence of the change in emission magnitude (8.59 Tg) and the global CH4 change (7.48 Tg) The change in the emission spatial distribution contributes more to the total BO3 change than the emission magnitude and methane changes combined.

Spatial distribution of ΔBO3 1. These features are more visible when we put them on a global map. The BO3 change is best explained by the spatial distribution change. The greatest BO3 increases are over South and Southeast Asia, suggesting that emissions increases here may be most important.

Zonal distributions of tropospheric O3 changes Total Spatial distribution Magnitude Global CH4 O3 increases significantly over 0°N-35°N (5-9 ppbv) in the middle and upper troposphere (750hPa to 150hPa), even greater than at the surface, and over 30°S-0°S at higher altitudes (4-7 ppbv). There are small O3 changes near the surface between 35°N-60°N, but obvious increases above the middle troposphere, even though the anthropogenic emissions over North America and Europe decrease between 1980 and 2010. The spatial distribution change best explains the overall change, particularly the regions with greatest ozone increases Latitude Latitude O3 increases most over 0°N-35°N (5-9 ppbv) in the middle and upper troposphere, and over 30°S-0°S at higher altitudes (4-7 ppbv). The spatial distribution change best explains the overall change.

Zonal distributions of tropospheric NOy changes Spatial distribution Total Magnitude Global CH4 We then discuss the conditions behind which makes the O3 burden change are more sensitive to the changes in the tropical regions. Emission increases South of 35ºN are transported efficiently to the middle and upper troposphere, due to strong tropical convection (Hadley cell). Emission decreases North of 35ºN stay at higher latitudes and lower elevation, due to Ferrell cell circulation. Latitude Latitude O3 precursors transported to the middle and upper troposphere in the tropics. Emission increases <35ºN are transported efficiently to the middle and upper troposphere, due to strong tropical convection (Hadley cell). Emission decreases >35ºN stay at higher latitudes and lower elevation.

O3-NOx-VOCs sensitivity Annual average surface ratios VOC-sensitive← → NOx-sensitive VOC-sensitive← →NOx-sensitive H2O2/HNO3 ratio H2O2/NO2 ratio Strong NOx-sensitivity is prevalent over tropical regions, especially in the middle and upper troposphere (not shown here), and emission trends show greater increases of NOx than of VOCs.

Conclusions Changes in the spatial distribution of global anthropogenic emissions from 1980 to 2010 dominate the tropospheric O3 burden change, even larger than the combined effect of the global emission magnitude and global CH4 change. O3 production is much more sensitive to emissions from tropical regions due to strong photochemical rates, NOx-sensitivity, and strong convection, despite a longer O3 lifetime in the tropics. Emissions increases from South and Southeast Asia may be particularly important for the global BO3 increase. The spatial distribution of emissions has a dominant effect on global tropospheric O3, suggesting that the future ozone burden will be determined mainly by emissions from the tropics. 1. continuing to shift southward could cause BO3 to continue to increase even if global emissions decrease.

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Global ozone precursors shifting southwards 6.4% ↑ 21.2% ↑ 6.0% ↑ Ozone precursors are increasing globally from 1980 to 2010. CO & NMVOCs increases at south of 30˚N, but decreases north of this latitude from 1980 to 2010. NOx increase south of 40˚N, but decreases north. The peak emission region shifts southwards. Emissions are from ACCMIP before 2000, and from RCP8.5 for 2010 Between 1980 and 2010, emissions of NOx and NMVOCs increased to the south of 40°N but decreased north of this latitude, while for CO, emissions increased south of 30°N but decreased to the north. Consequently, the latitude band with greatest emissions shifted from 40-50°N in 1980 to 30-40°N in 2010 for NOx and NMVOCs and from 30-40°N to 20-30°N for CO

Model evaluation 1. We compare the O3 trend from 1980 to 2010 at six long-term remotes sites between model outputs and observations, and found that the model reproduces the trend well. 2. By comparing model output with multi-year ozonesonde data, satellite data, aircraft campaigns, and ground-based observation data, though with a tendency to overestimate surface O3 The model reproduces the O3 trend from 1980 to 2010 at six long-term remote sites well. The model also performs well for O3 seasonal, spatial, and vertical distribution in 2010.

ΔBO3 at different latitudinal bands Then we take a look at the global O3 burden changes at different latitudinal bands. ∆BO3 from 1980 to 2010 are greatest over the tropical regions, from 30ºS to 30ºN (17.93 Tg). For different latitudinal bands, the effect of the change in emission spatial distribution changes is always larger than that from emission magnitude and global CH4, except for north of 60ºN.

Global O3 chemical production and loss rate Tropical regions have fast chemical reaction rates due to strong sunlight and high temperature.