Earth Science and Applications from Space National Imperatives for the Next Decade and Beyond (2007) / Chapter Skim
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9 Climate Variability and Change
9 Climate Variability and Change
Pages 257-303
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From page 257... ...
• Evaluation and assessment of model capability will increasingly be the focus of measurement activities; demonstrating model capability is likely to drive development and evolution of observation systems and field campaigns. • Higher-spatial-resolution observations, predictions, and assessments are needed to better establish the link between climate research and societal benefits.
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From page 258... ...
. Those strategies advocate a vigorous comparison of climate models and observations and a focus on specific observations that test how well climate simulations incorporate feedback processes and elucidate aspects of spatial and temporal variability.
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From page 259... ...
Changes in the volume of water stored on land as ice and snow are of critical importance to coastal populations and infrastructure because of the effects on sea level. Water resource management is strongly tied to climate and weather, and adaptation strategies are expensive and often require decades to implement.
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From page 260... ...
In its consideration of the specific observations to be made and the challenges and opportunities presented by the changes anticipated in the coming decade, the Climate Change and Variability Panel adopted the list of essential climate variables in the 2003 Global Climate Observing System report (GCOS, 2003)
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From page 261... ...
Global records of a few decades have been constructed from space-based observations of such variables as sea-surface temperature, sea ice, atmospheric layer temperatures, Earth's energy budget, and cloud properties. Overlapping observations are crucial for identifying and reducing calibration uncertainties in current instruments that would otherwise exceed the geophysical changes of interest.
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From page 262... ...
As originally proposed, NPOESS lacked the capabilities of the EOS-era satellite systems: VIIRS was missing important water vapor and temperature sounding channels, the capability of CMIS to provide useful passive winds was uncertain, OMPS had much lower horizontal resolution than Aura's ozone-monitoring instrument (OMI) and lacked limb sounding, and ALT's orbit made removal of tides a challenge.
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From page 263... ...
In addition to sea-ice mapping, passive microwave sensors are used to map the onset and extent of melt on the Greenland ice sheet, a key to assessing climate change and the contributions of ice-sheet melt to rising sea level. In view of the fundamental role played by accurate long-term Earth radiation budget measurements and in view of the growing gap expected between the CERES observations on Aqua and the ERBS observations now scheduled for C-1 (proposed date, 2013)
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From page 264... ...
Because of the uncertain future of instrument calibration within NPOESS and the likelihood of important data gaps, the development of a space-borne calibration observatory to address accurate radiometry and reference frequencies is essential. • For many variables, such as aerosol and cloud properties and water vapor concentrations, it is crucial to avoid orbital drift, which causes a substantial shift of several hours in the local time of the observations.
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From page 265... ...
Reliable climate simulations require improved treatment of the processes known to be inadequate (NRC, 2003c, 2005b) : clouds, aerosols, and convective systems; biosphere-atmosphere interactions; coupling of sea ice, ocean circulation, and icemelt; ice-sheet dynamics; the fluxes of heat, momentum, water, and trace species across the interfaces of ocean-atmosphere, land-atmosphere, ice-atmosphere, boundary layer and free troposphere, troposphere-stratosphere, and ice-ocean; and internal variability, such as the ENSO.
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From page 266... ...
The necessary drive to design observing systems that address known deficiencies in knowledge should not be allowed to preclude opportunities for ongoing curiosity-driven discoveries whose tremendous contributions can continue to revolutionize the Earth sciences. requirements for developing climate data from satellite Observations involvement of the climate science community The success of NASA's Earth Science Enterprise in developing records of climate variables that have been validated over long periods is unprecedented.
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From page 267... ...
There is also a pressing need for measurements of the vertical distribution of water vapor, cloud-ice and liquid-water path, and convective processes. Large-Volume, accessible archives of Long-term climate Observations Climate science requirements have substantial implications for data management, distribution, access, reprocessing, scientific oversight, and value-added analyses that are all part of comprehensive data stewardship.
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From page 268... ...
Some of the approaches listed in Table 9.A.1, like those involving Earth's radiation budget components, have benefited from decades of advancement; others, such as the characterization of cloud properties to come from the millimeter-wavelength cloud radar on CloudSat, are just beginning.3 The matrix approach, combined with the perspective in the "Overview" and analysis of climate science requirements in the "Observational Needs and Requirements" section above, has guided the development of a proposed set of missions. The missions are not intended to address the problems in the current NPOESS program.
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From page 269... ...
Mission Summary -- Clouds, Aerosols, Ice, and Carbon Variables: Aerosol properties, cloud properties, ice-sheet volume, sea-ice thickness, ocean carbon, land carbon Sensors: Scanning dual-wavelength lidar, multiangle visible/near-IR polarized spectrometer, hyperspectral imager, radar Orbit/coverage: LEO/global Panel synergies: Health, Ecosystems, Water, Weather Some of the most important uncertainties in global climate change are the role of different types of aerosols in Earth's radiation budget and hydrologic cycle; the importance of black carbon aerosols in suppressing clouds, altering precipitation and heating the atmosphere; the rate of change in ice sheet volume; the rate at which the oceans take up and sequester carbon; and the change in land carbon storage and vegetation characteristics. Those topics have been discussed by the IPCC, the decadal survey committee's
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From page 270... ...
while substantially advancing the technology to better accuracy, finer resolution and greater spatial coverage -- all necessary to understand aerosol-cloud interaction. The package would also address ice sheets and, with the addition of a hyperspectral imager on the same platform or coflying on its own satellite, can address the ocean and land carbon goals mentioned above.
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From page 271... ...
Ice Sheet and Sea Ice Volume Mass balance of Earth's great ice sheets and their contributions to sea level are key issues in climate variability and change. The relationships between sea level and climate have been identified as critical subjects of study in the IPCC assessments, the U.S.
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From page 272... ...
272 EARTH SCIENCE AND APPLICATIONS FROM SPACE 532 nm Total Attenuated Backscatter (km-1 sr-1) 30 25 20 Altitude (km)
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From page 273... ...
Given the rapidity of the change in polar sea ice and ice sheets (e.g., Yu et al., 2004; Zwally et al., 2005; Parkinson, 2006) and the remaining lifetime of ICESat, a critical gap would arise if the new measurements were not made before the launch of CM1 (possibly in 2015)
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From page 274... ...
ICESat's laser altimeter measures elevations over the entire ice sheet for the first time, including the steeper margins where mass losses are largest. The large areas of thinning (dark blue)
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From page 275... ...
The primary instruments are a multibeam altimetric lidar, a spectrometer-polarimeter, and a cloud radar. Another key objective is to obtain ice sheet and sea ice topography measurements and from them to estimate sea ice thickness and ice volume change.
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From page 276... ...
properties and height, cloud droplet spectropolarimeter, cloud radar distribution How is ice sheet volume changing? Altitude of ice sheets Multibeam altimetric lidar for ice sheet altimetry How is sea ice thickness changing?
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From page 277... ...
For more than two decades, Earth radiation-budget observations from ERBE and CERES have been used to assess climate model simulations of the radiation budget (Wielicki et al., 2002) , cloud radiative forcing (Potter and Cess, 2004)
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From page 278... ...
Radiance Calibration and Time-Reference Observatory Estimation of trends in the climate records of the TIROS-N series has been complicated by the lack of radiometric calibration of instruments on different platforms. Trend estimation direct from the measurements is further complicated by drifts in the orbits of the operational satellites, which cause shifts in the local times of the observations and in orbit altitudes; orbit drift is not a problem for modern assimilation systems.
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From page 279... ...
Two satellites would be placed in precessing orbits separated by 6 hours in equatorial crossing time. The third satellite would provide a backup in the event of failure of one of the orbiting satellites, thereby ensuring overlap of observations as desired for climate-data records (CCSP, 2003; Ohring et al., 2005)
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From page 280... ...
Continuity The Earth radiation budget has been measured continuously from space for more than 2 decades. The CERES project has demonstrated the capability of obtaining highly accurate radiative fluxes when the broadband radiances obtained with the radiometer are interpreted through scene identification achieved through the analysis of collocated multispectral imagery data (Loeb et al., 2003a, 2005)
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From page 281... ...
Highly accurate measurements of solar irradiances along with the energy budget of Earth represent fundamental climate variables that have revealed considerable information concerning the workings of the climate system; extension of the record of accurate measurements into the NPOESS era should lead to constraints on radiative forcing and climate sensitivity. Given the threat of a gap in the highly accurate multidecade record of Earth radiation-budget measurements, the panel recommends that the CERES FM-5, now awaiting launch on NPOESS C-1, be refurbished and flown on NPP.
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From page 282... ...
TABLE 9.2.2 Instruments and Science Objectives: RCTRO Radiation Budget and Radiance Calibration for Long-Term Temperature, Pressure, and Estimates of Instrument Atmospheric and Surface Properties Water Vapor Climate Sensitivity Shortwave spectrometer Primary NA Primary Thermal infrared spectrometer Primary Primary Primary Broadband active-cavity radiometer Primary NA Primary Filtered broadband active-cavity Primary NA Primary radiometer GPS NA Primary Primary GPS radio occultation on future NASA NA Primary Primary LEO missions and on NPOESS TABLE 9.2.3 Instrument Requirements: RCTRO Instrument Requirements Comments Orbit Three satellites: two in precessing orbits separated by 6 hours of crossing time, and one ready to launch Shortwave spectrometer 0.2-3 μm with a nadir field of view of about 100 km, steerable to achieve various view angles Thermal infrared 3-100 μm with a nadir field of view of about 100 km, steerable to achieve spectrometer various view angles Broadband active-cavity 0.2-100 μm with a nadir field of view of about 500 km, steerable to achieve radiometer various view angles Filtered broadband active- 0.2-3 μm broadband shortwave radiances with a nadir field of view of cavity radiometer about 500 km, steerable to achieve various view angles GPS receiver High-precision, high-stability oscillator GPS satellites With high-accuracy ultrastable oscillator; radio occultation receivers that can receive GPS, GLONASS, and Galileo radio signals
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From page 283... ...
broadband radiances from multiple ERBS follow-on sensors SIM, TSIS follow-ons TABLE 9.2.5 Instruments and Science Objectives: ERBS Continuation Instrument Radiation Budget Estimates of Climate Sensitivity Scanning radiometer Primary Primary SIM Primary Primary TABLE 9.2.6 Instrument Requirements: ERBS Continuation Instrument Requirements Comments Orbit Fly on NPP, 1:30 orbit Requires VIIRS for scene identification ERBS follow-ons on NPOESS C-1 and C-3 Scanning radiometers Modified CERES Flight Change mirror attenuator to improve on-orbit solar calibrations Model-5 Replace CERES narrow 8- to 12-μm window filter (one of three CERES channels) with the ERBE long-wave filter Spectral irradiance Fly on NPP or Glory monitor Requires solar pointing platform TSIS follow-ons on NPOESS C-1 and C-3
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From page 284... ...
Many of those processes are absent from current ice-sheet models, and many global climate models fail to include active ice sheets at all; this suggests that an important and variable component of the Earth system is being overlooked in climate prediction. Key scientific goals of Climate Mission 3 are to understand glaciers and ice sheets sufficiently to estimate their contribution to local hydrology and global sea-level rise and to predict their response to expected changes in climate, to understand sea ice sufficiently to predict its response to and influence on global climate change and biological processes, to measure how much water is stored as seasonal snow and its variability, and to understand the interactions between the changing polar atmosphere and the changes in sea ice, snow extent, and surface melting.
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From page 285... ...
The Antarctic sea-ice increases are also statistically significant, although at a much lower rate of +13,600 ±2,900 km2/yr. The Northern Hemisphere plot is extended from Parkinson et al.
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From page 286... ...
and with gravity measurements from a GRACE-type mission would yield much improved estimates of changes in ice sheet mass balance. The combination of measurements of ice-sheet motion, topography, and mass would yield a powerful tool for assessing changes in the ice sheets.
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From page 287... ...
, GRACE follow-on incorporation of ice sheets into climate models be improved? How can the contribution of ice sheets Fine-resolution measurement of surface InSAR, Climate Mission 1, GRACE to sea-level change be estimated motion, repeat measurements of better?
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From page 288... ...
(2006) suggests that the current climate models are overestimating heat uptake.
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From page 289... ...
. Climate Mission 4 is proposed as a 5-year satellite mission using a wide-swath radar altimeter to measure ocean surface topography globally (or at least throughout the non-ice-covered oceans, depending on the selected orbit; see discussion below)
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From page 290... ...
Box 9.4 summarizes the components of the panel's proposed Climate Mission 4. high-priority subjects requiring innovative approaches Some of the major issues in climate research require innovative measurement approaches beyond those proposed in the RFI responses and beyond those required for Climate Missions 1-4.
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From page 291... ...
winds How can knowledge of the mesoscale Sea-surface height, ocean vector Swath radar altimeter, scatterometer, GRACE-type ocean circulation and ocean-bottom winds follow-on topography be used to improve ocean-circulation models and understanding of ocean-atmosphere interaction? How is sea level changing?
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From page 292... ...
focus area Beta: Measurement of convective transports Atmospheric convection is a key process in climate models that is not well understood. Convection transports heat, water vapor, momentum, trace gases, and aerosols in the presence of clouds and mixed phases of precipitation.
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From page 293... ...
The problems of data continuity, relative and absolute calibration of the measurement sequence, open access to and availability of data, standardization of processing, and distribution standards must all be considered. interagency issues A number of institutional challenges must be addressed to achieve the full potential of the climate missions outlined above.
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From page 294... ...
The CLIVAR Climate Process Teams Program for in situ measurements is designed specifically to understand processes poorly handled by the climate models and provides a framework that could be adopted for a similar effort involving satellite measurements. The panel recommends a new cross-agency effort to foster a more fertile crossover between those collecting, managing, and analyzing satellite observations and the modeling groups.
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From page 295... ...
2003. The use of GPS measurements for water vapor determination.
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From page 296... ...
2003a. Angular distribution models for top-of atmosphere radiative flux estimation from the Clouds and the Earth's Radiant Energy System instrument on the Tropical Rainfall Measuring Mission Satellite.
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From page 297... ...
2005. Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002.
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From page 298... ...
TABLE 9.A.1 Climate Change and Variability Panel's Summary of Status of Major Climate Variables and Forcing Factors Measurement Follow-on RFI (GCOS) a Responseb Strategy Current Status (2010-2020)
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From page 299... ...
Stratospheric Limb and solar occultation HIRDLS on Aura, infrared radiometer None 63 aerosol properties, measurements SAGE II on ERBS (1984-2006) optical depth, size, Profile of aerosol extinction SAGE III on Meteor (2002-2006)
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From page 300... ...
, AIRS/AMSU on Aqua (2002) NPOESS GPS radio occultation GPS on CHAMP (2000)
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From page 301... ...
, COSMIC (2006) Mission 2 Profiles of temperature, water vapor with up to about 0.5-km vertical resolution near surface Surface network Radiosonde water-vapor profiles, WMO sonde network (1959)
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From page 302... ...
LDCM imagers ASTER on Terra (2000) Mission 1 Vegetation index at higher spatial EO-1 resolution Sea level Altimeter Jason 1 (2001)
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From page 303... ...
Mission 1 Rate for light drizzle aNumbers in parentheses refer to the essential climate variables listed in Appendix 1 of CGOS (2003)
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