Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2005
Publication Date: 12/15/2005
Citation: Eichinger, W.E., Holder, H.E., Cooper, D.I., Hipps, L.E., Knight, R., Kustas, W.P., Nichols, J., Prueger, J.H. 2005. Lidar measurement of boundary layer evolution to determine sensible heat fluxes. Journal of Hydrometeorology. 6:840-853.
Interpretive Summary: The estimation of large scale fluxes of heat and water vapor is crucial for a number of reasons, including weather prediction, climate, agriculture, and water resources management. It is known that these fluxes are not uniform and that the distribution of the surface heat fluxes is a major factor in producing and modifying atmospheric flows, and weather patterns. A main focus of SMACEX is the investigation of the interactions between the atmospheric flows, and soil-vegetated canopy system. A vertically staring ground-based Light detection and ranging (Lidar) system was used to provide a high time resolution, continuous record of lower atmospheric conditions at the edge between a soybean and cornfield. The properties of the lower atmosphere affecting interactions with the soil-vegetated canopy system were used in a model for estimating large-scale heat flux exchange. Heat flux estimates made over six days agreed with a network of conventional tower flux measurement systems. This result indicates a ground-based lidar system can provide reliable large area heat flux estimation useful for evaluating the accuracy of models used in weather forecasting agriculture and water resource management.
Technical Abstract: The Soil Moisture-Atmosphere Coupling Experiment (SMACEX) was conducted in the Walnut Creek Watershed near Ames, Iowa over the period from June 15 to July 11, 2002. A main focus of SMACEX is the investigation of the interactions between the atmospheric boundary layer, surface moisture, and canopy. A vertically staring elastic lidar was used to provide a high time resolution, continuous record of the boundary layer height at the edge between a soybean and a corn field. The height and thickness of the entrainment zone are used to estimate the surface sensible heat flux using the Batchvarova-Gryning boundary layer model. Flux estimates made over six days are compared to conventional eddy correlation measurements. The calculated values of the sensible heat flux were found to be well correlated (R2=0.79, with a slope of 0.95) when compared to eddy correlation measurements in the area. The standard error of the flux estimates was 21.4 W/m2, somewhat higher than a predicted uncertainty of 13.3%.