Lecture6_Water budget_biomes

Nowpack groundwater oceansalinity soilmoisture

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Unformatted text preview: CESat Measurements of Polar Ice ICESat Goal is to measure ice sheet mass balance: • detect average ice changes of ~ 1 cm/year • 1 cm = ~5% of annual mass input = ~ 0.001% of total ice mass • annual ice sheet mass changes = ~ ± 25 cm/yr = ~ ± 1 cm/yr sea level • current sea level rise totals approximately 2 mm/year due to: • melting of small glaciers, ocean thermal expansion, and ? ? ? ? 02 February 2005 Goddard Space Flight Center 52 Observing the Global Water Cycle ICESat Measurements of Polar Ice ► Science Objectives: ► Instrument: ► Geoscience Laser Altimeter System (GLAS) Weekly global update ~ 3 cm precision (over 100 km2) ~ 20 cm accuracy = ~ 1 cm sea level Future Goals: 02 February 2005 Polar Ice Sheet Mass Balance Cloud heights and aerosols Land topography surface water Improved (denser) spatial coverage Improved precision => mass balance Goddard Space Flight Center 53 Observing the Global Water Cycle Snow Cover and Water Content ► Need: Major annual water resource comes from snow melt Biosphere turns on/off at 0°C ► Goal: Measure Global Snow Cover and Water Equivalent on ecological and seasonal scales MODIS global snow cover map • Present and proposed measurements: – – – – snow cover: color measurements surface temperature: IR & microwave radiometry snow water content: Ku and Ka band Radiometer surface characteristics & vegetation: C and Ku band SAR; hyperspectral 02 February 2005 Goddard Space Flight Center 54 Observing the Global Water Cycle Cold Lands Mission ► Goals: Vastly improved measurement precision and accuracy Measure global snow cover and water equivalent ► ► 02 February 2005 on ecological and seasonal scales account for the effects of vegetation Goddard Space Flight Center 55 Observing the Global Water Cycle Aquarius Ocean Salinity Mission • Ocean Salinity: – – Drives thermo­haline circulation Investigate changes with climate variability Cool, saline water sinks, forms the ocean deep­water source Reduced salinity due to rainfall in inter­tropical convergence zone Increased salinity due to mid­ latitude evaporation 02 February 2005 Goddard Space Flight Center Increased salinity in Atlantic ocean … Why? 56 Observing the Global Water Cycle Aquarius Ocean Salinity Mission ► Why measure ocean salinity?: drives thermo­haline circulation ► links ocean circulation with the global water cycle a measure of ocean precipitation and evaporation ► How to measure ocean salinity?: Ocean emissions: L­band radiometer (GSFC) Sea surface roughness: L­band scatterometer (JPL) Monthly global coverage 80 km resolution 0.2 psu accuracy (0.1 K) 02 February 2005 Goddard Space Flight Center 57 Land Data Assimilation System (LDAS) Land Provides land surface states (snow depth, soil moisture, temperature, etc.) and fluxes (evaporation, etc.) for water resource applications. and APPROACH: Force land surface APPROACH: models with data from spacemodels based and ground observing based systems....
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