Elaine W. Gottlieb

Estimating regional carbon exchange in New England and Quebec by combining atmospheric, ground-based and satellite data

We derive regional-scale (∼104 km2) CO2 flux estimates for summer 2004 in the northeast United States and southern Quebec by assimilating extensive data into a receptor-oriented model-data fusion framework. Surface fluxes are specified using the Vegetation Photosynthesis and Respiration Model (VPRM), a simple, readily optimized biosphere model driven by satellite data, AmeriFlux eddy covariance measurements and meteorological fields. The surface flux model is coupled to a Lagrangian atmospheric adjoint model, the Stochastic Time-Inverted Lagrangian Transport Model (STILT) that links point observations to upwind sources with high spatiotemporal resolution. Analysis of CO2 concentration data from the NOAA-ESRL tall tower at Argyle, ME and from extensive aircraft surveys, shows that the STILT– VPRM framework successfully links model flux fields to regionally representative atmospheric CO2 data, providing a bridge between ‘bottom-up’ and ‘top-down’ methods for estimating regional CO2 budgets on timescales from hourly to monthly. The surface flux model, with initial calibration to eddy covariance data, produces an excellent a priori condition for inversion studies constrained by atmospheric concentration data. Exploratory optimization studies show that data from several sites in a region are needed to constrain model parameters for all major vegetation types, because the atmosphere commingles the influence of regional vegetation types, and even high-resolution meteorological analysis cannot disentangle the associated contributions. Airborne data are critical to help define uncertainty within the optimization framework, showing for example, that in summertime CO2 concentration at Argyle (107 m) is ∼0.6 ppm lower than the mean in the planetary boundary layer.

Urban/industrial pollution for the New York City–Washington, D. C., corridor, 1996–1998: 1. Providing independent verification of CO and PCE emissions inventories

Atmospheric mixing ratios of carbon monoxide (CO) and perchloroethylene (PCE, C 2 Cl 4 ) were measured above the canopy at Harvard forest, MA every half-hour for 3 years starting in January 1996. Pollution enhancements are strongly correlated with winds from the southwest, the direction of the New York City-Washington, D. C., corridor, as compared to background levels observed during northwest winds traveling from Canada. We establish the ratio of CO to PCE pollution enhancements by wind direction, by season, and by year and use these results to test the quality of county-level and national source emission inventories for these two gases. The EPA carbon monoxide emission county-level inventories and the McCulloch and Midgley sales-based national-level PCE release estimates are found to be in accord with our independent observations of urban/industrial releases. For the New York City-Washington, D. C., corridor the inventory-based CO I l PCE I emissions ratio of 584 (kg/kg) for 1996 falls well within the range of observationally-based ACO/APCE pollution plume ratios of 388 to 706 (kg/kg) and is only 11% higher than the observed mean of 521 ± 90 (kg/kg). On the basis of this agreement, PCE emission estimates for 1997 and 1998 are derived from the CO inventory emissions values and the observed ΔCO/ΔPCE ratios in pollution plumes for those years; despite the call for voluntary cutbacks, urban/industrial emissions of PCE appear to be on the rise.

Correction to “Seasonal controls on the exchange of carbon and water in an Amazonian rain forest”

Citation: Hutyra, L. R., J. W. Munger, S. R. Saleska, E. Gottlieb, B. C. Daube, A. L. Dunn, D. F. Amaral, P. B. de Camargo, and S. C.Wofsy (2007), Correction to ‘‘Seasonal controls on the exchange of carbon and water in an Amazonian rain forest,’’ J. Geophys. Res.,112, G04099, doi:10.1029/2007JG000573.