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Title:   Author  item
                                            GUZINSKI, R - University Of Copenhagenitem
                                            Anderson, Marthaitem
                                            Kustas, William

                                                         - *Bill*item
                                            NIETO, H - University Of Copenhagenitem
                                            SANDHOLT, I - University Of Copenhagen
  Submitted to: Hydrology and Earth System Sciences
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/16/2013
                                    Publication  Date: 7/16/2013
                                    Publication URL: http://handle.nal.usda.gov/10113/59954Citation: Guzinski, R., Anderson, M.C., Kustas, W.P., Nieto, H., Sandholt, I. 2013. Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations. Hydrology and Earth System Sciences. 17:2809-2825.Interpretive Summary: Remote sensing techniques for mapping land-surface water use (evapotranspiration, ET) have been developed using time-differential land-surface temperature (LST) data collected by geostationary satellites.  While these remote sensing techniques have proven to be quite valuable for large area mapping of water use and availability, they are not easily applied at high latitudes (above 60 degrees) where the geostationary satellite view angle is very oblique.  A new modeling approach is described that uses multiple LST images collected per day from polar orbiting satellite systems.  At high latitudes, the imaging frequency of these systems becomes quite high, approximating geostationary capabilities.  The resultant Dual Temperature Difference (DTD) model has been tested and refined over several flux measurement sites in the United States, and at high latitude sites in Denmark, using multiple images per day collected with the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the Terra and Aqua satellite platforms.  Model performance is quantified, and is consistent with results from the geostationary modeling framework.  In combination, these geostationary and polar orbiting ET mapping techniques can provide full global coverage and offer a means for monitoring water resources world-wide.
                                Technical Abstract: The Dual Temperature Difference (DTD) model, introduced by [Norman et al.(2000)], uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 hour after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows application of the DTD model to high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites.  A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation is developed and evaluated.  Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. Land-cover based modifications to the Priestley-Taylor scheme, used to estimate transpiration fluxes, are explored based on prior findings for conifer forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological Observatory (HOBE) in western Denmark, indicating realistic patterns based on land use.


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