14-HydroCycle_SnowColor - 5/21/2008 The Hydrologic Cycle...

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Unformatted text preview: 5/21/2008 The Hydrologic Cycle and the Color of Snow Spectral reflectance of clean snow Snow's spectral reflectance, with Landsat bands Snow/cloud discrimination with Landsat 3 Bands 3 2 1 (red, green, blue) Bands 5 4 2 4 Topics Spectral reflectance of snow and its variability Implications for energy balance of snowpack Measurement of snowpack energy exchange (Mammoth Mountain) Remote sensing of snow-covered area and albedo Fractional (subpixel) snow cover and grain size from MODIS, MODIS every day Time series corrections for clouds, viewing geometry, and other noise Relationship to hydrology Net solar radiation on snow over season Available for use by others for hydrologic models 6 ESM 266: Hydrologic cycle and the color of snow 1 5/21/2008 Seasonal solar radiation, Mammoth Mountain Snow is a collection of scattering grains Snow spectral reflectance and absorption coefficient of ice Spectral solar irradiance Net solar radiation Spectral reflectance of dirty snow and snow with red algae (Chlamydomonas nivalis) (Chlamydomonas nivalis) ESM 266: Hydrologic cycle and the color of snow 2 5/21/2008 Spectral mixture analysis, generalized Spectral mixture equation, per pixel Spectral residuals, per pixel SnowSnow-covered area in the Tokopah Basin (Kaweah River drainage), Sierra Nevada AVIRIS 21 May 1997 05 May 1997 18 June 1997 RMS error, per pixel MODSCAG spectrally mixes with range of snow endmembers and chooses the result with the least RMS error for that pixel 20 km Grain size in the Tokopah Basin (Kaweah River drainage), Sierra Nevada 21 May 1997 05 May 1997 Spectra with MODIS "land" bands 18 June 1997 20 km Fractional snow-covered area from MODIS snow- Why fractional area? ESM 266: Hydrologic cycle and the color of snow 3 5/21/2008 Validation, MODIS snow-covered area snow- MODISMODIS-derived albedo vs field measurements Tuolumne & Merced River basin elevations Effect of MODIS view angle Cloud identification (sometimes problematic over snow) Interpolate and smooth to fill missing values ESM 266: Hydrologic cycle and the color of snow 4 5/21/2008 Smoothing spline at a pixel Manual measurement of SWE (snow water equivalent) 26 Typical trends (Tuolumne R drainage) SnowSnow-pillow data for Dana Meadows and Tuolumne Meadows 1800 1600 1400 1200 SWE, mm 1000 800 600 400 200 0 2003 2005 2005 2003 DAN 1983 TUM 1983 10/01 11/01 12/01 01/01 02/01 03/01 04/01 05/01 06/01 07/01 28 Accumulation and ablation inferred from snow pillow data, Tuolumne Meadows and Dana Meadows TuolumneTuolumne-Merced 2005, snow-covered area vs snowelevation 29 ESM 266: Hydrologic cycle and the color of snow 5 5/21/2008 Snowmelt by elevation band June/July 2005 30 Snow in Tuolumne & Merced (2004 & 2005) 3450 contributions to snowmelt by elev band, m 25 Volumne snowmelt, 107 m3 Tuolumne 3750 Progressive contributions from higher elevation bands w/ time time. Little contribution from lowest or highest elevations. 20 15 3150 10 2850 5 36% (Tuolumne) 34% (Merced) snowmelt from above 3000m 13% (Tuolumne) 5% (Merced) snowmelt from below 2100m 7/15/05 2250 0 6/15/05 6/20/05 6/25/05 6/30/05 7/5/05 2550 7/10/05 Merced 3450 3150 Hi h surface measurement at 2918m Highest f 2918 Lowest surface measurement at 2100m Depletion over 2 months 2100-2400m, 4 months 2700-3000m 2850 Snow depletion maps provide a better quantitative basis for estimating basin-scale snow than do snow pillows 2550 2250 = X X [1 Applications: snowmelt modeling, Marble Fork of the Kaweah River Magnitude of snowmelt: Modeled Observed snow water equivalent SWE difference, cm AVIRIS albedo Melt Flux = ( R net mq +Td ar ) SCA degree days > 0 Snow Covered Area Tokopah basin, Sierra Nevada net radiation > 0 assumed w/ update assumed albedo where: mq = Energy to water depth conversion, 0.026 cm W-1 m2 day-1 ar = Convection parameter, based on wind speed, temperature, humidity, and roughness ar = ( co nve ctio n p arameter, b ased o n w ind speed , hu mi dit y, an d rou ghn ess) ESM 266: Hydrologic cycle and the color of snow 6 5/21/2008 Acknowledgments Steve Warren & Warren Wiscombe Model for the spectral albedo of snow (1980) Former and current students on this topic Bert Davis, Rob Green, Danny Marks, Noah Molotch, Anne Nolin,Tom Painter, Karl Rittger, Walter Rosenthal, Jiancheng Shi NASA Funding on remote sensing of snow since 1977 UC Santa Barbara Great place to think about snow and ice 37 ESM 266: Hydrologic cycle and the color of snow 7 ...
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This note was uploaded on 08/06/2008 for the course ESM 266 taught by Professor Dozier during the Spring '08 term at UCSB.

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