Prueger, John (USDA-ARS Ames, Iowa, National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA, 50011; Phone: 515-294-7694; Fax: 515-294-8125; Email: prueger@nstl.gov)

Comparison of Tower and Aircraft Eddy Covariance Measurement of CO₂ and H₂O Fluxes Over Corn and Soybean Fields in Central Iowa

J.H. Prueger *, J.L. Hatfield, W.P. Kustas

Individual field (corn or soybean, Zea mays L. and Glycine max (L.) Merr.) measurements of CO₂ and H₂O fluxes provide valuable information on exchange processes but are inherently limited to the individual fields in which the measurements were made. Scaling field measurements to watershed and regional scales has important implications to operational forecast models that focus on hydrological processes and carbon uptake. To achieve this goal, a set of direct-measurement/remote sensing/modeling approaches are needed to understand how horizontal heterogeneities in vegetation cover, soil moisture and other land-surface variables influence the exchange of H₂O and CO₂ with the atmosphere. The Soil Moisture Atmosphere Exchange study (SMACEX) was a combined measurement and modeling program with the intent to rigorously link remotely sensed data and operational forecast models. Previous field and remotely sensed observations support the analysis of heterogeneities that range from within field or patch scale (~100 m) to the regional scales that are commensurate with prediction models of weather and climate (10-100 km). In this paper we evaluate 12 eddy covariance/energy balance towers equally distributed across typical production size fields of corn and soybeans with measurements made with the Canadian Twin Otter aircraft. Comparison of mass and energy fluxes between tower and aircraft measurements was well correlated for net radiation, latent and sensible heat fluxes and CO₂ fluxes. Details of the measurement campaign, data processing and analysis will be presented.