Natasha Miles, Kenneth Davis, Scott Richardson, Thomas Lauvaux, and many MCI and INFLUX collaborators Symposium on Air Quality Measurement Methods and Technology 2 November 2010 Regional- and urban-scale measurements of greenhouse gases: RING2 and INFLUX projects

Fate of CO 2 emissions Large fraction (averaging ~45%) of fossil fuel emissions are absorbed Large interannual variability in sink strength Governed by climate variability (e.g. ENSO)? Source: Sarmiento and Gruber, Physics Today, 2003

Predicting future carbon fluxes C 4 MIP: comparison of 10 coupled climate/carbon models Large range of uncertainty (16 GtC yr -1 range in land flux by 2100) Total uncertainty less than sum of individual uncertainties Friedlingstein et al., in press

Tower-based CO 2 observations

Regional- and urban-scale CO2 measurements Previously published regional studies density on the order of 1 site / 10 6 km 2 CARBO-EUROPE: 2 sites / 10 5 km 2 Mid-Continent Intensive (MCI): RING2 Regional –scale deployment of CO2 mixing ratio measurements of unprecedented number, density: 9 sites / 5 x 10 5 km 2 INFLUX (Indianapolis Flux Project): Urban-scale deployment: 12 sites / 4 x 10 3 km 2 MCI RING2INFLUX

C CO 2, CO, CH 4 CO 2 CH 4 CO 2 CH 4 CO 2 CH 4 CO 2 C Mid-Continent Intensive (MCI) Overarching Goal Compare and reconcile to the extent possible, regional carbon flux estimates from “top-down” inverse modeling with the “bottom-up” inventories

Corn-dominated sites RING2: 9 sites measuring CO2 mixing ratio within 500 x 800 km 2

PSU RING2 towers Network of 5 cavity ring-down spectroscopy (Picarro, Inc.) instruments surrounding Iowa (April 2007 – October 2009) –Centerville, IA –Galesville, WI –Kewanee, IL –Mead, NE –Round Lake, MN Additional well-calibrated site on Ameriflux tower at Missouri Ozarks, MO NOAA tall towers in MCI region Non-dispersive infrared spectroscopy (LiCor, Inc.) instruments LEF (1994 – current) WBI (July 2007 – current) U. Of Minn Rosemount tower Tunable diode laser instrument May 2007 – current

Daily (weather-related) variability is large Corn and non-corn distributions overlap, but corn is wider with lower median While the vegetation type plays a role, advection is very important on a daily time- scale Daily variability corn non-corn

Large variance in seasonal drawdown, despite being separated by ~ km 2 groups: ppm drawdown and 24 – 29 ppm drawdown (difference of about 10 ppm) Mauna Loa

Large variance in seasonal drawdown, despite being separated by ~ km 2 groups: ppm drawdown and 24 – 29 ppm drawdown (difference of about 10 ppm) Mauna Loa

Large variance in seasonal drawdown, despite being separated by ~ km 2 groups: ppm drawdown and 24 – 29 ppm drawdown (difference of about 10 ppm) Mauna Loa

Seasonal variability Median differences between cross-vegetation pairs: 6 ppm ! Median gradients between cross-vegetation pairs: 2 ppm / 100 km ! – factor of 10 times as large as the ocean-continent gradient – factor of 100 times as large as the interhemispheric gradient

How much area does each tower “see”? Footprint size Footprint size depends on meteorology, sources and sinks in area Logarithmic scale (% of total for each pixel) About 39% of the variability (∆CO 2 /flux) originates with a 150- km radius of each tower. Conversely, 28% originates outside of the MCI domain. ~ 500 km

Implications of MCI RING2 results The atmosphere does not ‘mix out’ the persistent and strong seasonal-scale gradients. Model transport very important. Two distinct groups (corn-dominated and non-corn dominated): Implication for network design -> tower locations could be distributed based on geospatial data closely tied to NEE, such as NDVI and vegetation type The value of the additional sites in the MCI, as far as reducing uncertainties in fluxes derived from inversions, is yet to be determined.

INFLUX (Indianapolis FLUX) Project Goals: Develop improved approach for measurement of area-wide greenhouse gas emission fluxes within the urban area Compare top-down emission estimates from aircraft and tower-based measurements with bottom-up emission estimates from inventory methods Quantify uncertainties in the two approaches

Why Indianapolis? Medium-sized city, with fossil fuel CO2 emissions of ~3.4 MtC yr -1 Located far from other metropolitan areas, so the signal from Indianapolis can be isolated with relative ease Flat terrain, making the meteorology relatively simple View of Indianapolis from the White River (photo by Jean Williams) 1

Emissions data products: Vulcan and Hestia Arizona State Univ (K. Gurney): Bottom-up inventories Vulcan: 0.1° for U.S. Hestia: city block level (Indianapolis is test case)

Aircraft measurements Purdue University (P. Shepson, O. Cambaliza) : ALAR aircraft flights, beginning in fall 2010, will measure CO2/CH4 continuously, as well as sampling flasks and measuring meteorological data Two types of flights will be utilized: mass balance and source characterization Bi-weekly flights

Tower locations Site 1, upwind of the urban center, is located in Mooresville, IN, and provides “background” values. Site 2, located on the east of the city, measures the urban plume when the wind is aligned in the predominant southwest to northeast orientation. Sites 3 through 12 are planned, with ideal locations shown

Tower-based measurements: flasks NOAA (J. Turnbull, C. Sweeney): Flasks, filled preferentially when the wind direction is such that Site 2 is downwind of Site 1, measure the following: CO2, CO, CH4, 14CO2, 13CO2, N2O, SF6,H2, and a suite of halocarbons and hydrocarbons. All sites measuring CO continuously will be accompanied by flask measurements. The 14CO2 will be used to calibrate the CO as a fossil fuel CO2 tracer.

Tower-based measurements: continuous Penn State Univ (K. Davis, N. Miles, S. Richardson) Current: continuous measurements of CO2 at two sites Planned Two sites measuring CO2/CO/CH4 Three sites measuring CO2/CO Three sites measuring CO2/CH4 Four sites measuring CO2

25 – 27 October 2010 Wind direction predominately from the South West or South Site 02 generally higher [CO2] than Site 01 Site 02: East 21 st Street “Downwind” Site 01: Mooresville “Upwind” Site 02 downwind of Site 01 within 15° 0.7 Tower data: CO2 mixing ratios

Gradients up to 10 ppm / 100 km Biological gradients observed during RING2: 3 ppm / 100 km

Multi-species inversion set-up for urban emissions Nested grid ~20 km horizontal resolution for eastern United States ~1-2 km horizontal resolution for 50 x 50 km 2 inner domain Prior fluxes Vulcan CO2 inventory at 10 km resolution CH4 from NOAA (EPA based) at 4 km resolution Neglect the vegetation signal Solve for emission sources (residential, industrial, traffic) Fluxes to be estimated for each grid cell with weekly temporal resolution Atmospheric inversions Thomas Lauvaux (Penn State) Fluxes & Uncertainties Predicted [CO2] Transport Model & Uncertainties Obs. - Predicted [CO2] Obs. - Predicted [CO2]

RING2 Kenneth Davis, Natasha Miles, Scott Richardson, Thomas Lauvaux, Arlyn Andrews, Tristram West, Varaprasad Bandaru, Eric Crosson, Scott Denning Collaborators INFLUX Paul Shepson, Maria O. Cambaliza, Kenneth Davis, Natasha Miles, Scott Richardson, Thomas Lauvaux, Kevin Gurney, Colm Sweeney, Jocelyn Turnbull