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

underway and its utility can be assessed. Then we can alsoapply such methods to regions where in-situ data are largelylacking. Here we use a well-established global dischargeprediction model (WBM) to obtain estimated discharge timeseries for calibrating remote sensing measurements (usingthe Advanced Microwave Scanning Radiometer (AMSR-E)band at 36.5 GHz processed in the Global Flood DetectionSystem at the Joint Research Centre of the EuropeanCommission). We evaluate this methodology on a suite ofriver measurement sites in the U.S. for which we have in-situgaged discharge (from co-located USGS gaging stations) andalso for the Indus River, in Pakistan, where such data aremuch more limited. The preliminary results are promising;they show that model-predicted discharge can provide localrating equations for river measurement sites monitored onlyvia remote sensing. This allows immediate translation ofincoming remote sensing to discharge estimates, and furthertesting of the WBM model. The results also show thatmonthly or yearly discharge statistics (means, maximums,and minimums) are as useful as the daily time-series inproviding a first-order calibration to discharge.Collins, William D.A Comparison of the Scale Invariance of the WaterVapor Field Observed by the Atmospheric InfraredSounder to the Scale Invariance of In SituObservations from a Very Tall TowerPressel, Kyle G. 1, 2 ; Collins, William D. 1, 2 ; Desai, Ankur R. 31. Earth and Planetary Sciences, University of California,Berkeley, Berkeley, CA, USA2. Lawrence Berkeley National Laboratory, Berkeley, CA,USA3. Atmospheric and Oceanic Sciences Department,University of Wisconsin, Madison, Madison, WI, USAIt has recently been shown that the water vapor fieldobserved by the Atmospheric Infrared Sounder exhibitswidespread scale invariance at spatial scales ranging from50km to 500km. The lower length scale is determined by theresolution of the AIRS instrument. There is no a priorireason to expect that a scale break would occur until scalesthat are well below 50km. Observational support for anextension of the AIRS observed scale invariance to smallerscales would provide a basis for including the observed scaleinvariance of the water vapor field in the formulation ofsubgrid scale parameterizations in global climate models(GCMs). There are very few observations of the water vaporfield amenable to studying scale invariance at scales below50km. In this presentation we report results of an analysis ofscale invariance in time series of high frequency (10Hz)measurements of water vapor mixing ratio from the 396mlevel of the WLEF tower located near Park Falls, Wisconsin.In particular, we compute the first order structure functionof the WLEF water vapor time series. The first orderstructure function of the time series relates the mean oftemporal fluctuations, also know as increments, to timescale. If the first order structure function exhibits power lawdependence on scale then the field is said to be scaleinvariant. Taylor’s frozen turbulence hypothesis is used totransform the time scales of the structure functions toapproximate spatial scales. In this study we have computedpower law exponents for the first structure function ofdetrended 4 hour time series sampled from June, July, andAugust of 2006 through June 2011. The 4 hour time seriesroutinely allow computation of the structure function toscales in excess of 16km. It is found that while not allstructure functions suggest scale invariance of the watervapor field, those that do exhibit scale invariance showevidence of a diurnal cycle in power law exponents that isremarkably consistent with the diurnal variation of AIRSobserved exponents.Connor, WilliamStrategies for validating Vegetation IndexEnvironmental Data Records from Visible InfraredImaging Radiometer Suite using tower reflectancemeasurementsConnor, William 1 ; Miura, Tomoaki 11. Natural Resources and Environmental Management,University of Hawaii at Manoa, Honolulu, HI, USASpectral vegetation indices (VIs) from satellite remotesensing have been shown useful to derive inputs tolandscape-scale modeling of Earth’s hydrological cycle, suchas fractional vegetation cover and evapotranspiration (ET).For example, the vegetation index – surface temperatureapproach is a popular approach for quantifying surface ETresistance. Realized ET from land surfaces are a function ofsurface properties, where physiological activity of vegetationis especially important as it limits evapotranspiration belowpotential level. The National Polar-orbiting OperationalEnvironmental Satellite System Preparatory Project (NPP) isthe first step in building the next-generation Earthobserving satellite. Onboard the NPP is the Visible InfraredImaging Radiometer Suite (VIIRS), a key component of theNPP spacecraft, which will provide detailed imagery, orEnvironmental Data Records (EDRs), of vegetation andother geophysical parameters. Two VIs, the normalizeddifference vegetation index (NDVI) and enhanced vegetationindex (EVI), collected daily at 375 m resolution have beenincluded as one of VIIRS EDRs. In order to ensure accuraterepresentation, validation is one critical component of theVIIRS EDR development. One planned validation activity forVIIRS Vegetation Index EDRs is to use tower-basedreflectance measurements to continuously assess accuracy ofVI EDRs and their time series, aimed at anchoring satellitedata to the ground. In tower-based reflectancemeasurements, a spectrometer is typically mounted at thetop of a tower, acquiring bi-hemispherical reflectancecontinuously at set intervals. Footprints of these tower-basedreflectance measurements are typically smaller than thespatial resolution of VIIRS VI EDRs. Therefore, it is arequirement to evaluate spatial representativeness of thetower measurements for the VIIRS spatial resolution. In thisstudy, we developed a protocol to evaluate spatialrepresentativeness of a site for VI validation and applied it to48