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

Sturm, MatthewRemote Sensing and Ground-based SnowMeasurements: Limitations, Strengths, andOptimal BlendingSturm, Matthew 1 ; Liston, Glen 21. Terrestrial Sciences Branch, U.S.A. Cold Regions Research& Engineering Laboratory-Alaska, Ft. Wainwright, AK,USA2. Cooperative Institute for Research in the Atmosphere,Colorado State University, Ft. Collins, CO, USAAll snow measurements share six attributes: 1) support(S), 2) extent (E), 3) spacing (P), 4) repeat frequency (), 5)accuracy (A) and 6) work effort (W). Table I contrasts theseparameters for remote sensing vs. ground-basedmeasurements. Measurement resolution is a function of S, Eand P: the smaller S and P, the higher the resolution, butonly if E spans the snow structures or gradients of interest.Work effort (W) increases dramatically as E increases and Sand P decrease. Accuracy is related to S but in complex ways.In the case of remote sensing products, accuracy is alsodependent on having an appropriate and well-calibratedalgorithm and understanding how small-scale variationsaggregate electromagnetically, an area where ourunderstanding is currently limited. An optimal observingsystem would have a small support, a large extent, a closespacing, a low work effort, high repeat frequency, and highaccuracy. This appears to be impossible to achieve, so thebest hope is to blend systems, building on the strengths ofeach system, reconciling scaling weaknesses in each methodthrough clever combinations, using models to blend the two.We illustrate this idea using ground and remote sensing datafor snow-covered areas in Colorado and Alaska.http://www.crrel.usace.army.mil/sid/personnel/sturm.matthew.htmlTable I: Comparison of Remote and Ground-based MeasurementsSultan, MohamedAn Integrated (remote sensing, GIS, hydrogeology,geochemistry, geophysics, and hydrologicmodeling) Approach for a Better Understanding ofthe Hydrology of the Nubian Aquifer, NE AfricaSultan, Mohamed 1 ; Ahmed, Mohamed 1 ; Sturchio, Neil 2 ; Yan,Eugene 3 ; Milewski, Adam 4 ; Becker, Richard 5 ; Wahr, John 6 ;Becker, Doris 5 ; Chouinard, Kyle 11. Dept Geosciences, Western Michigan Univ, Kalamazoo,MI, USA2. Earth and Environmental Sciences, University Illinois atChicago, Chicago, IL, USA3. Environmental Sciences, Argonne National Laboratory,Argonne, IL, USA4. Geology, University of Georgia, Athens, GA, USA5. Environmental Sciences, University of Toledo, Toledo,OH, USA6. Physics, University of Colorado at Boulder, Boulder, CO,USAIntegrated studies (remote sensing, GIS, hydrogeology,geochemistry, geophysics, and hydrologic modeling) wereconducted to investigate the hydrologic setting of theNubian Sandstone Fossil Aquifer of northeast Africa, and toassess the response and of the system to climatic andanthropic forcing parameters. Results indicate: (1) theNubian Aquifer System is more likely to be formed of anumber of discrete sub-basins that are largely disconnectedfrom one another; (2) potential paleo-recharge areas weredelineated from SRTM and SIR-C data; (3) areas receivingmodern natural recharge were identified in northern Sudanand northeast Chad and locally in central and southernSinai using TRMM data; (4) recharge was estimated at 13.0 x10 6 m 3 by using a continuous rainfall-runoff model; (5) totalrecharge (10 11 m 3 ) from Lake Nasser to the aquifer wassimulated by using a calibrated groundwater flow model forperiods of high lake levels (1975 to 1983: 6 x10 10 m 3 ; 1993 to2001: 4 x 10 10 m 3 yr -1 ); (5) previously unrecognized naturaldischarge locations were identified by remote sensing,geophysics, and geochemistry, and quantified withhydrologic models along the River Nile basin and the Gulf ofSuez fault complexes; (6) analysis of monthly GRACE (April2002 through November 2010) indicated near steady-statesolutions in the south (Sudan: 8 mm yr -1 ; Chad: -9 mm yr -1 )and in Libya (-11 mm yr -1 ) and declining water supplies inEgypt (-35 mm yr -1 ) largely related to progressive increase inextraction rates with time.137