1. ring2.psu.edu Natasha Miles, Scott Richardson, Ken Davis, and Eric Crosson American Geophysical Union Annual Meeting 2008: 17 Dec 2008 Temporal and spatial variability in regional-scale CO 2 mixing ratios as measured during the Mid-Continental Intensive study

2. Outline Mid Continental Intensive, Ring 2 Temporal variability Spatial gradients Seasonal cycle –Comparison to NOAA- ESRL CarbonTracker June 2008 flood in midwest Explaining small and large spatial gradients using a regional flux model (forwards)

3. NACP Mid-Continental Intensive WLEF ~ 500 km Overall goal: Seek convergence between top-down (tower-based) and bottom-up (inventory-based) ecological estimates of the regional flux Focus on upper Midwest of the U.S. Add regional network of 5 communications-tower based atmospheric CO2 obs in the midcontinent intensive region –April/May 2007 through October 2008 Plan: to “oversample” the atmosphere in the study region for more than a full year Inversions to produce maps of fluxes of CO2 for region (CSU) The role of Ring 2 in the Mid-Continent Intensive “Ring 2” Cavity Ring- Down systems PSU Ameriflux systems NOAA Tall Towers

4. Instrumentation Details: Ring 2 Cavity ring-down spectroscopy (Picarro, Inc.) –Long-term stability –Much reduced need for calibration over NDIR methods Both [CO2] and [H2O] are measured 30 and 110-140 m AGL Quality control –Two reference gases at each site, sampled ~daily –Round-robin tests (Feb and Nov 08) –Uncertainty: < 0.2 ppm

5. Synoptic variability in boundary-layer CO2 mixing ratios Seasonal drawdown Differences amongst the sites 2007 vs 2008 Day to day variability

6. Difference in daily value from one day to the next: as large as 10-30 ppm Synoptic variability in boundary-layer CO2 mixing ratios Seasonal drawdown Differences amongst the sites 2007 vs 2008 Day to day variability

7. Temporal variability: Night – Day [CO2] Difference between nighttime and daytime values at ~120 m AGL can be over 80 ppm for Ring 2 Average magnitude of the diurnal cycle at 122 m for July at LEF: 10 ppm (1995-1997) (Bakwin et al. 1998)

8. Temporal variability: Night – Day [CO2] Difference between nighttime and daytime values at ~120 m AGL can be over 80 ppm for Ring 2 Average magnitude of the diurnal cycle at 122 m for July at LEF: 10 ppm (1995-1997) (Bakwin et al. 1998) LEF Ring2

9. Spatial gradient magnitude (daytime): Growing seasons 2007-08 Majority < 0.02 ppm/km But in 6% of cases, the spatial gradient is between 0.04 and 0.06 ppm/km (Daytime!) % of site-days Seasonal pattern Differences as large as 40 - 50 ppm between Ring 2 sites! Daytime! Significant day-to-day variability Largest difference amongst the sites for each daily value

10. Seasonal cycle Strong coherent seasonal cycle across stations West Branch (wbi) differs significantly from 2007 to 2008 Large variance in seasonal drawdown, despite being separated by, at most, 550 km. (mm, ce, lef) vs (kw, rl, wbi) mlo

11. Seasonal cycle Strong coherent seasonal cycle across stations West Branch (wbi) differs significantly from 2007 to 2008 Large variance in seasonal drawdown, despite being separated by, at most, 550 km. (mm, ce, lef) vs (kw, rl, wbi) mlo

12. Seasonal cycle Strong coherent seasonal cycle across stations West Branch (wbi) differs significantly from 2007 to 2008 Large variance in seasonal drawdown, despite being separated by, at most, 550 km. (mm, ce, lef) vs (kw, rl, wbi) mlo

13. Dominant vegetation map Corn for Grain 2007 Yield per Harvested Acre by County Courtesy of K. Corbin

14. NOAA-ESRL Carbon Tracker Ring2 sites not included as input for 2007 http://carbontracker.noaa.gov

15. 14-day smoother applied to CT output mid-afternoon values only (19:30 GMT) Overall drawdown in CT2008 is too weak, but some features of modeled variability are consistent with obs, e.g., there is a lot of variability and MM has less drawdown than WBI, RL and KW in both model and obs. A. Andrews 2007

16. Flooding in the Midwest: June 2008 Dell Creek breach of Lake Delton, WI U.S. Air Force Cedar Rapids, IA Don Becker (USGS)

17. Seasonal cycle Strong coherent seasonal cycle across stations West Branch (wbi) differs significantly from 2007 to 2008 Large variance in seasonal drawdown, despite being separated by, at most, 550 km (mm, ce, lef) vs (kw, rl, wbi)

18. Delay in seasonal drawdown 2008 growing season is uniformly delayed by about one month, compared to 2007 Effect of June 2008 flood? Recovery: increased uptake later in the growing season 2007 solid 2008 dashed 20072008

19. Regional flux model: forward results SiB3-RAMS coupled with crop phenology model for corn and soybean Addition of crops greatly improved model’s agreement with obs Gradients of daily minimum value: obs vs model Simulated CO2 at 120 m above ground level on 16 July 2007, illustrating advective controls on CO2 gradients observed across the Ring2 towers B51A-0364 Corbin et al. Effects of Agricultural Production on Regional Variations of Atmospheric CO2 Concentrations B51A-0355 Lokupitiya et al. Evaluation of the performance of SiBCrop model in predicting carbon fluxes and crop yields in the croplands of the US mid continental region

20. Summary Temporal variability –diurnal cycle magnitude large compared to LEF –2008 flood in the Midwest US Spatial gradients: large difference between sites despite relatively small site separations Seasonal cycle: –difference amongst sites, some with very large seasonal drawdown Comparisons to NOAA-ESRL CarbonTracker –Weak overall drawdown, but good variability