1. Indianapolis flux (INFLUX) in-situ network: quantification of urban atmospheric boundary layer greenhouse gas dry mole fraction enhancements 18 th WMO/IAEA Meeting on Carbon Dioxide, Other Greenhouse Gases and Related Measurement Techniques (GGMT), Sept 2015 N. Miles, S. Richardson, T. Lauvaux, K. Davis, A.J. Deng, D. Martins, C. Sweeney, A. Karion, J. Turnbull, K. Gurney, R. Patarasuk, I. Razlivanov

2. INFLUX: Indianapolis FLUX

3. Inventory sector-by-sector emissions (Hestia) Aircraft flights with CO2, CH4, and flask samples Automobile surveys of CH4 Ethane measurements (Feb - Mar 2015) TCCON-FTS (Sept - Dec 2012) 4 eddy-flux towers (installed Nov 2013) Doppler lidar (installed Apr 2013) 6 NOAA automated flask samplers (Turnbull et al., 2014) 12 surface towers measuring CO2, 10 with CH4, and 5 with CO Mesoscale atmospheric inversion INFLUX methodology:

4. INFLUX Tower Measurement Network Predominant wind direction

5. INFLUX in-situ tower measurements Picarro sensors at communications towers 39-136 m AGL Air sample dried using Nafion dryer Field calibration tank(s) sampled every 23 hours Round-robin testing using 3-4 NOAA-calibrated tanks (Nov 2013 and Sept 2015) Comparisons with NOAA 1-hour integrated flask samples

6. Enhancement: defined as difference between each potential background site and the INFLUX minimum for that hour Site 01 is the best overall background site Also Site 09 (when the wind is from the SE) Evaluation of potential background sites: INFLUX in-situ CO 2 observations 1 Jan – 30 Apr 2013 Afternoon hours 01 04 05 09 city Wind “perfect”

7. Enhancement: defined as difference between each potential background site and the INFLUX minimum for that hour Site 01 is the best overall background site Also Site 09 (when the wind is from the SE) Evaluation of potential background sites: INFLUX in-situ CO 2 observations 1 Jan – 30 Apr 2013 Afternoon hours 01 04 05 09 city Wind “perfect”

8. Evaluation of potential background sites: INFLUX in-situ CO 2 observations 1 Jan – 30 Apr 2013 Afternoon hours 1 4 01 04 05 09 city Enhancement: defined as difference between each potential background site and the INFLUX minimum for that hour Site 01 is the best overall background site Also Site 09 (when the wind is from the NW/SE)

9. INFLUX in-situ tower measurements Daily afternoon averages Seasonal signal is apparent Significant overlap between sites 2011 2012 2013 2014 2015

10. INFLUX in-situ tower measurements Afternoon averages with 21-day smoothing Seasonal and synoptic cycles are evident 2011 2012 2013 2014 2015

11. INFLUX in-situ tower measurements Afternoon averages with 21-day smoothing Seasonal and synoptic cycles are evident

12. 2011 2012 2013 2014 2015 INFLUX in-situ tower measurements Afternoon [CO 2 ] with 21- day smoothing Seasonal and synoptic cycles are evident Harding Street Power Plant is switching from coal to natural gas by 2016 …

13. INFLUX in-situ tower measurements Afternoon averages with 21-day smoothing Seasonal and synoptic cycles are evident Downtown (Site 03): high [CO 2 ] Background (Site 01): low [CO 2 ] 2011 2012 2013 2014 2015

14. Observed CO 2 : afternoon values, averaged Jan-April 2013 (Dormant season) Site 09: 0.3 ppm larger than Site 01 Site 03: larger [CO 2 ] by 3 ppm Miles et al., in prep Spatial structure of urban CO 2 : observed BACK- GROUND

15. “Well-mixed” conditions: when do they occur? About 50% of days have achieved 80% of the drawdown for the day by 12 LST (17 UTC) 12 LST 15 LST

16. Observed time-averaged afternoon CO 2 dry mole fraction above background (Site 01) for INFLUX tower sites (1 January – 30 April 2013) averaged over different hours of the day (1700–2100 UTC, 2000–2300 UTC, and 2200 UTC), and a time-lagged version in which the CO 2 dry mole fraction at Site 01 at 1900 UTC is subtracted from the other sites’ CO 2 dry mole fraction at 2200 UTC. Spatial structure of urban CO 2 : effect of choice of averaging hours

17. Observed CH 4 : afternoon values, averaged Oct – Dec 2013 (Dormant season) Ranges from 5 ppb at Site 13 (10 km east of the city) to 21 ppb at Site 10 (near the landfill). Miles et al., in prep Spatial structure of urban CH 4 : observed Landfill

18. Observed CO: afternoon values, averaged Jan-April 2013 (Dormant season) Ranges from 6 ppb at Site 09 (24 km downwind of the edge of the city), to 29 ppb at Site 03 (downtown). Miles et al., in prep Spatial structure of urban CO: observed

19. High resolution inverse modeling - Weather Research and Forecasting model (WRF) : 9km/3km/1km (nested) - Four Dimensional Data Assimilation (FDDA) - Coupled to backward Lagrangian model - Kalman matrix inversion using Hestia 2013 emissions as a priori Lauvaux et al., in prep

20. INFLUX: Urban scale inversion Errors are significantly reduced after inversion, from 25% to 9% on average Posterior emissions higher Sept to mid Nov Total posterior emissions are 10% higher than Hestia Lauvaux et al., in prep Case: Background = Site 1 hourly Total Hestia : 4750 ktC Total Posterior : 5231 ktC 5-day emissions (ktC) 50 100 150 200 Date Inverse emissions (ktC): Sept 2012 to April 2013

21. 4 Sites (B) 4 Sites (A) 4 Sites (L=4km) Low Traffic Low Utility Hourly Transport Error 10-day window 20-23 UTC Daily Min Wind Model Post ODIAC Large σ B 2 L=12km L=4km L=0km Hestia (prior emissions) ODIAC Lauvaux et al., in prep Inverse emission estimates using different inverse system configurations and prior emissions 4.0 4.5 5.0 5.5 6.0 6.5 Inverse emissions (MtC): Sept 2012 – April 2013 Initial configuration

22. Conclusions Tower observations detect a clear urban signal in CO2/CH4/CO (buried amid lots of synoptic “noise”). Average afternoon dormant-season enhancements are as high as 21 ppb CH4 29 ppb CO 3.0 ppm CO2 The inverse emissions and Hestia are within 10% for the period Sept 2012 - April 2013. 16 different configurations with very different assumptions yield similar results. For more information, see influx.psu.edu