2012 AGU Chapman Conference on Remote Sensing of the ...

climate associated with hydrological changes is expected tobe small.compared to the SEBAL version without any modification,and it significantly discriminated ET among 75.8% ofvegetation types, at threshold differences in ET 0.5mm/day.Figure 1Figure 2Mariotto, IsabellaApplication of SEBAL Modified for TopographicReflectance and Roughness to Map the SpatialDistribution of ET in a Heterogeneous AreaMariotto, Isabella 1, 2 ; Gutschick, Vincent P. 21. Soil, Water, Environmental Science, University ofArizona, Tucson, AZ, USA2. Global Change Consulting Consortium, Inc., Las Cruces,NM, USAThis study presents a methodology to build advancedenergy balance algorithms to map ET in a heterogeneoussemi-arid area presenting 12 different land covers rangingfrom sand dunes to grassland and shrublands. The SurfaceEnergy Balance Algorithm for Land (SEBAL) was modifiedfor the roughness term and for the albedo and vegetationindex by respectively incorporating a plant heightcomponent and a non-Lambertian topographic correction ofreflectance. Corrections were performed using a GISraster/vector platform integrated with ASTER thermal andreflectance imagery, and terrain and land cover data. SEBALcomputed with the modifications showed the bestagreement with the eddy covariance flux measurements,97McCabe, Matthew F.Multi-model regional scale estimation ofevapotranspirationMcCabe, Matthew F. 1 ; Ershadi, Ali 1 ; Evans, Jason 11. School of Civil and Environmental Engineering,University of New South Wales, Sydney, NSW, AustraliaAccurate estimation of surface heat fluxes is ofconsiderable interest to meteorological, climatological andagricultural investigations as they identify the key physicalprocesses that link the land surface with the atmosphere.While characterising surface fluxes is critical in describingthe partitioning of water and energy across Earths terrestrialsurfaces, accurately monitoring the spatial variation,particularly at daily and sub-daily scales, is notoriouslydifficult. Spatial and temporal scaling issues, errors inforcing variables, heterogeneity in surface characteristics andsimplifications in process understanding, all limit thecapacity to accurately monitor flux development andvariability. Here, common approaches such as the Penman-Monteith formulation are considered alongside remotesensing based techniques, surface energy balance retrievalsand coupled regional climate model output to examine thevariation and consistency within these different estimationapproaches. The work is discussed in the context of aninternational collaborative effort to develop a globalobservationally based climatology of surface heat fluxes,which is being coordinated by the GEWEX Radiation Panel.McCabe, Matthew F.Intercomparison of flux measurement approaches:eddy covariance, scintillometers and remotesensing retrievals over a grasslandMcCabe, Matthew F. 1 ; Ershadi, Ali 1 ; Graham, Peter 11. School of Civil and Environmental Engineering,University of New South Wales, Sydney, NSW, AustraliaThe accurate estimation of surface heat fluxes using insitubased instrumentation is of considerable importance,particularly in the evaluation of spatially distributed remotesensing based retrievals using satellite and other data. Usingthree recently installed instruments at the BaldryHydrological Observatory in the central-west of NSW inAustralia, an evaluation of these different estimationtechniques is undertaken through instrumentintercomparison and also using common meteorologicalestimation approaches, such as the Penman-Monteith andprofile methods. Remote sensing based retrievals are alsoexamined to establish the degree of spatial variability at thesite and the representativeness of ground based datacollections.