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

constraints on carbon NPP, and information about NPPprovides significant constraints on the partition of ET intotranspiration and soil evaporation. We present recent workon the Australian water and carbon cycles in which a model(CABLE-SLI-CASAcnp) is constrained jointly withobservations of streamflow from several hundred gaugedcatchments, eddy flux measurements of ET and NEE (netecosystem exchange of carbon), remotely sensed data onvegetation state, and data on carbon pools (both in-situ andremotely sensed). As well as yielding a consistent picture ofwater and carbon exchanges, these joint constraints suggestthat on the Australian continent, a predominantly semi-aridregion, over half the water loss through ET occurs throughsoil evaporation and bypasses plants entirely. Second, againat regional scale, human forcings of carbon and water cyclespropagate into each other, and both are affected by largescaleclimate forcing. This is a question of dynamics ratherthan informatics. One manifestation is the joint response ofrunoff to warming, CO2 increase and precipitation changes.We use sensitivity tests with the CABLE-SLI-CASAcnp modelto explore this question for the Australian continent.Reager, John T.Effective global soil parameters from GRACE andimpact on land surface simulationsReager, John T. 1 ; Lo, MInhui 2 ; Blum, David 2 ; Famiglietti,James 1, 2 ; Rodell, Matthew 31. Earth Systems Science, University California, Irvine,Irvine, CA, USA2. UC Center for Hydrological Modeling, Irvine, CA, USA3. NASA GSFC, Greenbelt, MD, USAEffective values of soil depth and soil water holdingcapacity are critical hydrological variables in land surfacemodels. In global-scale simulations, these spatially variableparameters are often poorly represented due to observationaland scaling limitations. Some parameters, such as porosity,matric potential and soil conductivity, are based empiricallyon two-dimensional maps of soil types. Other critical soilcharacteristics however, such as soil layering and depth tobedrock, are assumed to be homogeneous in space, imposingan unrealistic constraint on climate model estimates ofgroundwater recharge and water storage in unconfinedaquifers, limiting the reliability of projections of future wateravailability. GRACE observations of terrestrial water storageanomaly are well-suited for estimating the effective range ofsuch land surface model parameters as soil depth and waterholding capacity, based on the spatial variability of thestorage signal. Here we combine GRACE storageobservations with GLDAS output for surface, canopy andsnow water, to derive a 1-degree spatially variable sub-surfaceactive water holding capacity. We use this result with globalestimates of porosity from the FAO Harmonized SoilDatabase to produce an effective 1-degree global active soillayer depth. The calculated depth and water holding capacityvariables can be introduced directly into a model, or used toderive other model parameters. In this study, we evaluate thesensitivity of numerical simulations to realistic waterholding capacity by incorporating our new estimates intothe CLM. Impacts on evaporation and surface radiation inoffline simulations and improvements to simulatedterrestrial hydroclimatology are discussed.Reeves, JessicaUncertainty in InSAR deformation measurementsfor estimating hydraulic head in the San Luis Valley,ColoradoReeves, Jessica 1 ; Knight, Rosemary 1 ; Zebker, Howard 11. Stanford University, Stanford, CA, USAThe San Luis Valley (SLV) is an 8000 km2 region insouthern Colorado that is home to a thriving agriculturaleconomy. The valley is currently in a period of extremedrought, with county and state regulators facing thechallenge of developing appropriate management policiesfor both surface water and ground water supplies.Legislation passed in 2004 requires that hydraulic head levelswithin the confined aquifer system stay within the rangeexperienced in the years 1978 - 2000. While somemeasurements of hydraulic head exist, greater spatial andtemporal sampling would be very valuable in understandingthe behavior of the confined aquifer system. Interferometricsynthetic aperture radar (InSAR) data provide spatially densemaps of surface deformation, with one pixel representing thetime series deformation of a 50 m by 50 m area on theground. Our long-term goal is to use these deformation timeseries to estimate hydraulic head. Here we present theanalysis of InSAR data from the European Space Agency’sERS-1 and ERS-2 satellites, using 31 acquisitions archivedfrom 1992 - 2001. We applied small baseline subset (SBAS)analysis to create a time series of deformation that issampled at the 31 acquisition times. We find that theseasonal deformation measured by InSAR mimics hydraulichead measurements made in the confined aquifer system.These measurements can be used to inform groundwatermanagers about the state of the groundwater system.However, at present little work has been done to quantify theuncertainty associated with InSAR image sequences ofaquifers. We have quantified the uncertainty in the InSARdeformation measurement that is caused by thedecorrelation of the two SAR signals. The correlation of theSAR signals is affected by: the local surface slope, theproperties of the surface, the time between two acquisitionsand the change in satellite position between twoacquisitions. We first quantified the variance and covarianceof the interferometric phase for all interferograms. We thenpropagated this uncertainty through the SBAS processingchain to produce the variance of the final estimates ofdeformation. We have shown that the uncertainty in thedeformation estimated at each acquisition time depends ona) the correlation of the SAR signals throughout time, andb) the number of interferograms used to estimate thedeformation at a given acquisition time. This understandingof the uncertainty in the InSAR measurement will allow usto rigorously assess how InSAR data can best be used to122