Submitted to: Boundary Layer Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2004
Publication Date: April 1, 2005
Citation: Crow, W.T., Kustas, W.P. 2005. Utility of Assimilating Surface Radiometric Temperature Observations for Evaporative Fraction and Heat Transfer Coefficient Retrieval. Boundary-Layer Meteorology. 115:105-130. Interpretive Summary: Remote sensing provides a powerful tool for estimating fluxes of energy and water between the land surface and lower atmosphere. Knowledge of these fluxes in critical for a number of key agricultural applications (e.g. crop water stress monitoring and irrigation management). Recent advances in land data assimilation techniques have yielded new methods for efficiently merging simple land surface model predictions with remote observations of surface temperature. Proponents of these methods claim they a number of advantages versus existing approaches that use remotely sensed data but do not employ data assimilation . This paper evaluates these claims and makes detailed comparisons between model predictions and ground truth surface flux data. Shortcomings of the data assimilation approach are described for the first time and potential modifications are presented to address them.
Technical Abstract: Recent advances in land data assimilation have yielded variational smoother techniques designed to solve the surface energy balance based on remote observation of surface radiometric temperature. These approaches have a number of potential advantages over existing diagnostic models including the ability to make energy flux predictions between observation times and reduced requirements for ancillary parameter estimation. Here, the performance of a recently developed variational smoother approach is examined in detail over a range of vegetative and hydrologic conditions in the southern United States through comparisons with flux tower observations and energy balance results obtained from the Two-Source Energy Balance model. Results identify circumstances under which the simultaneous retrieval of both evaporative fraction and turbulent transfer coefficients by variational approaches will be difficult and discuss parameter interpretation issues associated with the employing a single-source geometry for surface radiometric temperature.