1. Mapping Greenhouse Gas Emissions in the Los Angeles Basin by Remote Sensing Using a Fourier Transform Spectrometer on Mt. Wilson Kam Weng (Clare) Wong 1, Dejian Fu 1, Thomas Pongetti 1, Sally Newman 2, Eric Kort 1, Charles Miller 1, Yuk L. Yung 2, Stanley Sander 1 1 Jet Propulsion Laboratory, Pasadena, CA, USA 2 California Institution of Technology, Pasadena, CA, USA Copyright 2013. California Institute of Technology. Government sponsorship acknowledged.

2. Why Cities Matter? Sources: Duren and Miller, 2012 Photo of nightlight as seen from space showing global distribution of human activities.

3. Why Cities Matter? Cities contributes to the third most GHG emissions in the world, following the United States and China. About 50% of world’s population lives in cities (increase to 70% in 2050). It is important to track their emissions. Sources: Duren and Miller, 2012 Source: World Bank, 2010 Photo of nightlight as seen from space showing global distribution of human activities

4. Why Cities Matter? Sources: Duren and Miller, 2012 Here, we focus on the Los Angeles basin, one of the biggest megacities in the world. Source: World Bank, 2010 Cities contributes to the third most GHG emissions in the world, following the United States and China. About 50% of world’s population lives in cities (increase to 70% in 2050). It is important to track their emissions.

5. Sources of CO 2 in the LA Basin Vehicles Natural gas fueled power plants Anthropogenic CO 2 emissions in the LA basin primary comes from fossil fuel combustion. Vehicles and power plants are important sources. Emissions are understood to within 5-10% (California Air Resources Board, 2008)

6. Sources of CH4 in the LA Basin Pipeline leakage Landfills Wastewater treatment plants Methane (CH 4 ) comes from a variety of sources in the LA basin such as wastewater treatment plants, landfills, daily farms and pipeline leakage. Emissions in the LA basin have 25- 50% uncertainties (Wunch et al., 2009; Hsu et al., 2010; Wennberg et al., 2012). Dairy farms

7. How do we estimate emissions? Top-down Approach -- quantifies emissions based on direct observations of atmospheric concentrations. Essential to develop precise emission inventories. Ratio analysis is a simple way of estimating emission based on observations of atmospheric concentrations of 2 or more trace gases, when the emission of one of the trace gases is known.

8. The current network of continuous CO 2 and CH 4 measurements is very sparse. These observations may be limited to local area which may not represent the entire Los Angeles basin. Problems and Motivations Current continuous CO 2 and CH 4 monitoring stations 100 km

9. The current network of continuous CO 2 and CH 4 measurements is very sparse. These observations may be limited to local area which may not represent the entire Los Angeles basin. Problems and Motivations Current continuous CO 2 and CH 4 monitoring stations There is a need to develop a robust measurement technique which provides continuous temporal and spatial observations in LA basin! 100 km

10. Direct Beam (diffuse reflection from Spectralon plate) Azimuthal Scan Surface Reflection (Elevation Scan) FTIR Spectrometer (0.7-2.5  m) Pointing Mirror 16” Cassegrain Telescope (removable)  CO 2 at 1.6  m, 2.0  m  CH 4 at 1.6  m, 2.1  m  N 2 O at 2.3  m  CO at 2.3  m  O 2 at 1.27  m California Laboratory for Atmospheric Remote Sensing (CLARS) Long: 118.057°W Lat: 34.221°N Alt: 1.7 km (ASL) Two modes: 1.Direct sun 2.LA Basin Survey  Data filter for clouds/aerosol High-precision data since Aug 2011

11. Basin Reflection Points Standard measurement cycle: FTS points at the 28 reflection points (LA Basin Survey) and makes four direct sun measurements (integration time ~ 2.5 min). There are about 5-8 measurement cycles per day. Special measurement cycle: Specific targets, transects

12. Direct Sun West Pasadena Direct Sun and West Pasadena Observations In the following slide, we will compare the direct sun and the West Pasadena observations of path-averaged dry air mixing ratios, XCO 2 and XCH 4.

13. Direct sun measurements, which are above the urban dome, show no diurnal variations. Basin measurements show strong diurnal variations due to basin emissions. Diurnal Variations of Direct Sun and Basin XCO 2 and XCH 4 4/18/2012 4/19/20129/17/2012 9/18/2012 CO 2 CH 4

14. 1.Compute the XGAS excess above background resulting from emissions in the basin, by subtracting the direct sun XGAS from the basin XGAS. 2.Correlate the two XGAS excess to investigate the CH 4 :CO 2 emission ratio in the basin. Understanding the Emissions of CH 4 and CO 2

15. Tight correlations between XCO 2 and XCH 4 excess are observed (for all 28 basin measurements) even though the two GHGs have different sources, due to: CO 2 and CH 4 are emitted with relatively constant ratio, combined with mixing and ventilation processes in the atmosphere. Correlations Between CH 4 and CO 2

16. Spatial Variability of CH 4 :CO 2 Ratio in the LA Basin Atmosphere CH 4 :CO 2 ratios show spatial variability, ranging from 5.2 to 7.2 Average CH 4 :CO 2 ratio over all basin measurements is 6.2 +/- 0.23 Increasing distance from Mt. Wilson

17. OBSERVATIONSCH 4 :CO 2 RATIO (ppb:ppm) TYPE OF MEASUREMENT REFERENCES TCCON FTS (Pasadena, 8/2007 – 6/2008) 7.8±0.8ColumnWunch et al. 2009 CLARS FTS Pasadena, 9/2011 – 10/2012) 7.2±0.2ColumnThis study ARCTAS-CARB (LA basin, 6/2008) 6.8±0. 6Aircraft in-situWennberg et al. 2012 CalNex, LA basin (LA basin, 5/2010 – 6/2010) 6.6±0. 3Aircraft in-situWennberg et al. 2012 CLARS FTS (LA basin, 9/2011 – 10/2012) 6.2±0.2ColumnThis study Comparison with Previous Studies Results of this study are In good agreement with previous studies: In Pasadena

18. OBSERVATIONSCH 4 :CO 2 RATIO (ppb:ppm) TYPE OF MEASUREMENT REFERENCES TCCON FTS (Pasadena, 8/2007 – 6/2008) 7.8±0.8ColumnWunch et al. 2009 CLARS FTS Pasadena, 9/2011 – 10/2012) 7.2±0.2ColumnThis study ARCTAS-CARB (LA basin, 6/2008) 6.8±0. 6Aircraft in-situWennberg et al. 2012 CalNex, LA basin (LA basin, 5/2010 – 6/2010) 6.6±0. 3Aircraft in-situWennberg et al. 2012 CLARS FTS (LA basin, 9/2011 – 10/2012) 6.2±0.2ColumnThis study Comparison with Previous Studies Results of this study are In good agreement with previous studies: In Pasadena In the LA basin

19. This study demonstrates the ability to measure CO 2 and CH 4 in the Los Angeles basin using ground based remote sensing technique from Mt. Wilson. Observations indicate the current CH 4 emission inventory for the Los Angeles basin are underestimated by 20±5%. Spatial variability in CH 4 :CO 2 ratio is observed in the Los Angeles basin, indicating the need for ground based remote sensing of CO 2 and CH 4 from Mt Wilson. The long term goal is to assimilate the CO 2 and CH 4 observations and to improve CO 2 and CH 4 emission inventories for the Los Angeles basin using atmospheric inversion models. Conclusions

20. This study demonstrates the ability to measure CO 2 and CH 4 in the Los Angeles basin using ground based remote sensing technique from Mt. Wilson. Observations indicate the current CH 4 emission inventory for the Los Angeles basin are underestimated by 20±5%. Spatial variability in CH 4 :CO 2 ratio is observed in the Los Angeles basin, indicating the need for ground based remote sensing of CO 2 and CH 4 from Mt Wilson. The long term goal is to assimilate the CO 2 and CH 4 observations and to improve CO 2 and CH 4 emission inventories for the Los Angeles basin using atmospheric inversion models. Conclusions

21. This study demonstrates the ability to measure CO 2 and CH 4 in the Los Angeles basin using ground based remote sensing technique from Mt. Wilson. Observations indicate the current CH 4 emission inventory for the Los Angeles basin are underestimated by 20±5%. Spatial variability in CH 4 :CO 2 ratio is observed in the Los Angeles basin, indicating the need for ground based remote sensing of CO 2 and CH 4 from Mt Wilson. The long term goal is to assimilate the CO 2 and CH 4 observations and to improve CO 2 and CH 4 emission inventories for the Los Angeles basin using atmospheric inversion models. Conclusions

22. This study demonstrates the ability to measure CO 2 and CH 4 in the Los Angeles basin using ground based remote sensing technique from Mt. Wilson. Observations indicate the current CH 4 emission inventory for the Los Angeles basin are underestimated by 20±5%. Spatial variability in CH 4 :CO 2 ratio is observed in the Los Angeles basin, indicating the need for ground based remote sensing of CO 2 and CH 4 from Mt Wilson. The long term goal is to assimilate the CO 2 and CH 4 observations and to improve CO 2 and CH 4 emission inventories for the Los Angeles basin using atmospheric inversion models. Conclusions

23. Thank you! Questions?