Earth Science and Applications from Space National Imperatives for the Next Decade and Beyond (2007) / Chapter Skim
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11 Water Resources and the Global Hydrologic Cycle
11 Water Resources and the Global Hydrologic Cycle
Pages 338-380
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From page 338... ...
It controls the growth of plants through water availability related to soil moisture and through radiation reaching the land surfacecontrolled largely by cloudsthat is available for photosynthesis. Evaporation and transpiration from plants act to transfer not only water vapor but also energy from the surface to the atmosphere, enabling a feedback that has important implications for precipitation over global land areas.
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From page 339... ...
The scientific challenge posed by the need to observe the global water cycle is to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The vision to address that challenge is a series of Earth observation missions that will measure the states, stocks, flows, and residence times of water on regional to global scales followed by a series of coordinated missions that will address the processes, on a global scale, that underlie variability and changes in water in all its three phases.
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340 EARTH SCIENCE AND APPLICATIONS FROM SPACE 1978 2000 FIGURE 11.2 Changes in the Qori Kalis Glacier, Quelccaya Ice Cap, Peru, from 1978 to 2000. SOURCE: Courtesy of L
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From page 341... ...
SOURCE: See www.hydro.washington.edu/forecast/monitor.shtml. Courtesy of Land Surface Hydrology Research Group, University of Washington.
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342 EARTH SCIENCE AND APPLICATIONS FROM SPACE BOX 11.1 cONtiNued FIGURE 11.1.2 Replicate photographs of Lake Powell at the confluence with the Dirty Devil River (entering from left)
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From page 343... ...
Among the key deficiencies is information about the space-time distribution of soil moisture and snow-water storageinformation that is nearly impossible to obtain from in situ sensors but would be produced by the SMAP and SCLP mission concepts proposed in the section "Prioritized Observation Needs." 100,000 66,881 Mm 3 90,000 (1971 to 1994 avg) 80,000 70,000 Storage (Mm3)
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From page 344... ...
and society is also required. Better water-cycle observations, especially on the continental and global scales, will be essential.
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From page 345... ...
Estimation of river discharge from space remains an elusive goal. Having high-quality estimates of those variables, coupled with measures of surface-water storage and transport, would substantially improve the ability to model and understand the amounts and flows of surface water and in turn to provide an integrated understanding of the water cycle globally.
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From page 346... ...
In addition to measurements that would be made by these four missions, several measurements that would benefit analyses of the water cycle were highly rated by the water-cycle panel but with somewhat lower priority. They include missions that would estimate water vapor transport, sea ice and glacier mass balance, groundwater and ocean mass, and inland and coastal water quality (see Table 11.1)
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From page 347... ...
, and the water resources panel repeats that recommendation here: The panel recommends that GPM be launched in a timely manner, without further delay. NpOess NPOESS was originally intended to include several measurements that are of key importance to understanding climate and the global water cycle.
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From page 348... ...
. Accurate flood forecasting requires good knowledge of the initial state of the land system (primarily soil moisture and, where relevant, snow-water storage)
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From page 349... ...
The missions proposed the section "Prioritized Observation Needs" will especially improve the ability to estimate initial conditions for flood forecasting: the proposed SMAP soil-moisture mission will provide direct estimates of near-surface soil moisture, the SCLP cold-lands mission will provide estimates of snow-water storage, and the SWOT swath altimetry mission will provide estimates of initial conditions of river levels and floodplain storage. Other missions, such as atmospheric moisture profiles and transport, will also help to improve weather forecasts, especially in parts of the world where in situ (e.g., radiosonde)
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From page 350... ...
Hence, NPOESS would not obviate the need for a dedicated soil-moisture mission. The nadir-pointing ocean altimeter would not have addressed the needs outlined in the section "Sea Ice Thickness, Glacier Surface Elevation, and Glacier Velocity" of either the hydrology or the oceanography community for high-resolution swath altimetry.
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From page 351... ...
centimeters Ecosystems SMAP topography circulation interferometer, (vertical) Health microwave Weather GPM radiometer, GPS NPP/NPOESS receiver Snow, cold land Snow-water SAR, passive Global 100 m 3-15 days Climate SCLP processes equivalent, snow microwave Ecosystems depth, snow radiometry Weather wetness Water vapor Water vapor Microwave Global Vertical Weather 3D-Winds transport profile; wind Climate PATH speed, direction GACM GPSRO Sea ice thickness, Sea ice thickness, Lidar, InSAR Global Climate DESDynI glacier surface glacier surface Solid Earth ICESat-II elevation, and elevation; glacier glacier velocity velocity Groundwater Groundwater Laser ranging 100 km Climate GRACE-II storage, ice sheet storage, glacier Solid Earth mass balance, mass balance, ocean mass ocean mass distribution Inland, coastal Inland, coastal Hyperspectral Global or regional 45 m (global)
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From page 352... ...
For example, the WOWS and water-cycle mission concepts would have additional and higher-frequency microwave channels for snow, ocean winds, salinity, precipitation, and other variables. The MOSS concept would add a lower-frequency (VHF)
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From page 353... ...
complementarity The soil moisture and freeze-thaw estimates from SMAP -- as measurements of key components of the terrestrial hydrosphere -- will contribute to the disciplinary sciences throughout the Earth system community. Because soil moisture determines rates of energy and moisture exchange between the land surface and atmosphere and is a critical measure of the terrestrial portion of the water cycle, numerous branches of basic and applied Earth science require this measurement, including operational weather applications, climate science and seasonal climate forecasting, and terrestrial ecology and carbon-cycle science.
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From page 354... ...
The SMAP components and system are all at technology readiness level 7 and higher. surface Water and Ocean topography Mission summary -- surface Water and Ocean topography Variables: River and lake elevation; ocean circulation Sensors: Radar altimeter, nadir SAR interferometer, microwave radiometer, GPS receiver Orbit/coverage: LEO/global Panel synergies: Climate, Ecosystems, Health, Weather Related RFI responses: Hydrosphere Mapper (56)
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From page 355... ...
. When averaged over surface water areas of about 1 km2 and linear distances of 10 km for slope (assuming a 100-m-wide river channel)
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and WatER (108) RFI responses and is called SWOT (Surface Water and Ocean Topography)
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From page 357... ...
Because the open ocean lacks fixed elevation points, additional sensors are required to attain the desired height precision: the microwave radiometer to estimate the tropospheric water vapor range delay, and the GPS receiver for a precise orbit. A potential side benefit is that the GPS receiver could in principle also be used to provide radio occultation soundings (see the section "Water Vapor Transport" below)
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From page 358... ...
The swath altimeter would provide a basis for estimating coastal currents, ocean eddies, and global sea level. In addition to the benefits related to the land-surface water cycle and oceanography, a swath altimetry mission would have important scientific benefits related to weather and climate prediction, floodplain hydrodynamics, aquatic ecosystem and carbon dynamics, mesoscale currents and eddies, coastal processes, and ocean bathymetry.
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From page 359... ...
The altimetric observations of eustatic sea-level change, when compared with estimates of mass change measured with GRACE and GRACE-II, would allow partitioning of the sea-level change between thermal expansion and increased ocean mass. Multidisciplinarity The surface water mission concept contributes observations needed for studies of climate variability and change; weather; human health and security; land-use change, ecosystem dynamics, and biodiversity; solid-Earth hazards and dynamics; and societal benefits of Earth science and applications, in addition to water resources and the global hydrologic cycle.
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From page 360... ...
, snow depth, and snow wetness over land and ice sheets at 100-m spatial resolution and 3- to 15day temporal resolution. The proposed measurement approach will use dual-mode high-frequency (X- and Ku- band)
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science Value In the global water cycle, terrestrial snow is a dynamic freshwater reservoir that stores precipitation and delays runoff. Snow properties influence surface water and energy fluxes and other processes important for weather and climate, biogeochemical fluxes, and ecosystem dynamics.
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cost Near the center of the range of cost options (about $300 million) , the fundamental baseline mission concept is a dual-frequency, dual-polarization SAR combined with a dual-frequency radiometer at 19 and 37 GHz with H-polarization.
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From page 363... ...
and MODIS, as well as passive microwave radiometers such as SMMR, SSM/I, and AMSR-E, by increasing the spatial resolution over that of previous passive sensors. Since the passive microwave measurements from SCLP are at the same frequencies as those of the past and present space-borne radiometers, the SCLP measurements can contribute to a sustained record of over 25 years of passive microwave observations of snow properties.
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From page 364... ...
. Other high-priority Water-cycle Observations Water Vapor transport Mission SummaryWater Vapor Transport Variables: Water vapor profile; wind speed and direction Sensors: Passive microwave; GPS Orbit/coverage: LEO/global Panel synergies: Weather, Climate Related RFI responses: AIRS (8)
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From page 365... ...
That shortcoming is mitigated by its additional capabilities to measure ocean circulation, oceanic evaporation, and air-sea interaction and to map the cryosphere. sea ice thickness, Glacier surface elevation, and Glacier Velocity Mission Summary -- Sea Ice Thickness, Glacier Surface Elevation, and Glacier Velocity Variables: Sea ice thickness, glacier surface elevation, glacier velocity Sensors: Lidar, InSAR Orbit/coverage: LEO/global Panel synergies: Climate, Solid Earth Related RFI responses: InSAR (83)
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From page 366... ...
and the continuation of the observation record would provide invaluable observations of long-term climate-related changes in the mass of the Antarctic and Greenland ice sheets and large Arctic ice caps. Longer records that would allow better characterization of interannual changes in soil moisture and groundwater storage for use by hydrologists and for use in global land surface models would also result, although the coarse spatial resolution will continue to be a critical constraint.
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The figure shows time series (September 1997-October 2000) of organic matter and sediment near the mouth of the Mississippi River (top panels: A, 1-2)
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From page 368... ...
The spectral range of 350-1,050 nm and spectral resolution of 1 nm would provide the capability to monitor rapid changes in water quality in coastal regions, such as the onset and dynamics of algal blooms and ocean surface eutrophication. NeXt-GeNeratiON chaLLeNGes In the previous section, the panel ranked seven mission concepts that will make key contributions to water-cycle science.
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and carbon flux in the surface carbon balance. Evaporation also codetermineswith precipitationthe rate of the global water cycle.
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The water cycle operates on a continuum of time and space scales and exchanges large amounts of energy as water undergoes phase changes and is moved from one part of the Earth system to another. A central challenge of a future water-cycle observation strategy is to progress from single-variable water-cycle instruments to multivariable integrated water-cycle instruments, probably in electromagneticband families.
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The simultaneous multichannel active and passive microwave measurements would allow improved-accuracy retrievals of dimensions that were the focus of several Explorer-class mission concepts. To be concise, that means that the multiple instruments are not just sharing a spacecraft.
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From page 372... ...
, 0.1 mm (ocean) prediction • Rain rate: 5 mm/hr • Improve weather prediction and Snow water equivalent: 3 cm characterization of moist processes in models • Sea-surface salinity: • Monitor coastal and open-ocean climate 0.2 practical salinity unit variability and water cycle • Extend capabilities for climate and weather prediction would improve soil-moisture retrieval by avoiding the need for auxiliary vegetation information.
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From page 373... ...
particles and affect their growth to precipitation-size particlesas well as influencing the opacity of clouds to sunlightthe close interaction among these processes is evident. The main objective of an integrated cloud-aerosol-precipitation mission would be to provide a more quantitative basis for predicting changes in the planet's hydrologic cycle and energy balance as a step toward prediction of severe weather, climate, and climate change with much higher confidence than now exists.
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From page 374... ...
For instance, one cannot understand or forecast runoff trends, including floods, without first knowing about precipitation. Lead responsibility for observing various aspects of the water cycle crosses NASA, NOAA, USGS, and USDA.
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From page 375... ...
And a snow and cold lands mission would estimate the water storage of snowpacks, especially in spatially heterogeneous mountainous regions that are the source areas for many of the world's most important rivers. Taken together and in coordination with in situ and airborne sensors, these four missions would form the basis of a coordinated effort to observe the terrestrial surface water cycle globally.
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From page 376... ...
They include missions that would estimate water vapor transport, sea ice thickness and glacier mass balance, groundwater storage and ocean mass, and inland and coastal water quality (see Table 11.1)
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attachMeNt Table 11.A.1 lists 47 responses to the decadal survey committee's RFI (see Appendixes D and E) that were considered by the Panel on Water Resources and the Global Hydrologic Cycle for possible relevance to the water cycle.
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From page 378... ...
and models to discriminate and quantify particulate and dissolved carbon species in coastal waters, as well as the exchanges of carbon between the land, atmosphere, and ocean 23 C-CAN Continuous Coastal Awareness Network will measure sea surface height, coastal currents and winds and sea spectral reflectance from different Earth vantage points at high spatial and/or temporal resolution 25 Daedalus Daedalus: Earth-Sun Observations from L1: Simultaneously observe key solar emission/space weather parameters and spectrally resolved radiances over the entire illuminated Earth to characterize the direct influence of solar variability on the Earth system 27 WOWS Water and Ocean Wind Sensor using active and passive microwave concepts 36 Emory CU Surge GPS to measure ocean wind speed/direction, sea surface height and land surface soil moisture 38 FLORA Global, high spatial resolution measurements of vegetation composition, ecosystem processes and productivity controls, and their integrated responses to climate 42 Grace Follow-on Mission GRACE follow-on 44 GISMO Glaciers and Ice Sheets Mapping Orbiter 46 Global Water Resources An international effort consisting of about two dozen satellite systems, each of which Mission is comparable with current operational GEO and LEO satellites 49 GPS-HOT High resolution/high temporal revisit oceanography mission for mesoscale process characterization, will also yield data suitable for global tsunami warning 50 H2S Ocean Emissions H2S emitting from ocean surface 55 Human-Induced Land Detecting Human Induced Land Degradation Impact on Semi-Arid Tropical Rainfall Degradation Variability. Uses satellite-derived precipitation data, satellite-derived vegetation index data (no apparent observation program proposed)
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From page 379... ...
and at useful soil depths (2-5 meters) 71 GEOCarb Explorer GEOCarb mission will provide continent-wide measurements of ecosystem carbon and water dynamics with multiple observations per day 72 Multiplatform InSAR Forest Subcanopy Topography and Soil Moisture 74 Suborbital Earth System UAVs to be used for synoptic weather, hurricanes, air quality, stratospheric ozone, Surveillance ozone depleting substances, greenhouse gases, ice sheets, forest fires, droughts, and storm damage 76 Far IR Far-Infrared for understanding natural greenhouse effect, atmospheric cooling by water vapor, and the role of cirrus clouds in climate 79 Integrated Water Cycle Coordinated water cycle observations from space Observations 80 Low-Cost Multispectral Earth Global land observation system that enhances Landsat and OLI with stereo Observing System multispectral imaging, greater coverage, revisit (eight days and better)
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From page 380... ...
380 EARTH SCIENCE AND APPLICATIONS FROM SPACE TABLE 11.A.1 Continued RFI Response Number Response Title Comment 99 SH2OUT Sensing of H2O in the Upper Troposphere 100 GPM Global Precipitation Mission 103 Surface Observatories in Surface observations of water vapor, temperature, and winds, plus surface radiative Support of Observations of fluxes and cloud and aerosol properties Aerosols and Clouds 104 Terra-Luna Earth-Moon science mission that would provide Earth measurements over a relatively short period during Earth-orbiting phase, revisited at intervals of a decade or so, including boreal and tropical forest land cover and biomass mapping, global ocean eddies, coastal currents and tides, and land cover and canopy height 107 Water Vapor Monitoring Missions 108 WatER The Water Elevation Recovery Satellite Mission 110 Climate-Quality Observations Lidar measurements to address the themes of climate variability and change, weather, from Satellite Lidar and water resources and the global hydrologic cycle 111 Advanced ICESat Ice Cloud and land Elevation Satellite NOTE: A complete list of RFI responses is provided in Appendix E Full-text versions of the responses are included on the compact disk that contains this report.
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