Climate Calibration Observatory RoadmapDecadal Survey Mission Concept Bruce Wielicki, NASA LaRC CERE

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Climate Calibration Observatory Roadmap/Decadal
Survey Mission ConceptBruce Wielicki, NASA
LaRC (CERES)Kory Priestley, NASA LaRC
(CERES)Peter Pilewskie, Colorado Univ.
(SORCE)Tom Stone (USGS Lunar ROLO project)Dave
Siegel UCSB (SeaWIFS, ocean color)Chuck McClain,
NASA GSFC (ocean color)Warren Wiscombe, NASA
GSFC (Leonardo)Joe Rice, NIST (Discover)Francesc
o Valero (Discover)John Harries, Imperial
College UK (GERB)Marty Mlynczak, NASA LaRC
(Far-IR Interferometry)Jim Anderson, Harvard
(Climate Interferometry)Kevin Trenberth, NCAR
(climate goals advisory)
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Climate Calibration Observatory Mission

• Why a Satellite Calibration Observatory?
• Anthropogenic forcing is 0.6 Wm-2/decade
• Tropical 20S to 20N AMIP annual mean climate
  noise is 0.3 Wm-2
• Global net radiation annual mean sigma is 0.4
  Wm-2 (ERBS)
• 50 uncertainty in cloud feedback is change in
  cloud net radiative forcing of 0.3 Wm-2/decade.
  25 uncertainty is 0.15 Wm-2/decade.
• Suggests threshold of 0.3 Wm-2 global net cloud
  forcing and goal of 0.15 Wm-2 for stability per
  decade.
• 0.15 Wm-2 SW cloud forcing is 0.15/50 0.3 of
  global mean
• 0.15 Wm-2 LW cloud forcing is 0.15/30 0.5 of
  global mean
• 0.15 Wm-2 in clear-sky LW flux is 0.1C
  temperature change/decade
• Converting to cloud optical depth/height/temperatu
  re for imagers
• equivalent visible channel stability is 0.5
  stability per decade
• equivalent cloud height/temperature is 15m or
  0.1K stability per decade
• Temperature/Water Vapor Sounding 0.04 to 0.08K
  per decade.
• Vegetation and Ocean Color 1 reflectance
  stability per decade.

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Tropical (20S - 20N) TOA Radiation
AnomaliesObservations vs. Climate Models

• Model "noise" 0.3 Wm-2
• Climate Signals 2 Wm-2
• Net tropical heating in 90s
• Opposite sign of "Iris"
• Climate Forcing 0.6 Wm-2 / decade
• 50 Cloud Feedback 0.3 Wm-2 / decade
• 0.5 of TOA LW CRF
• 0.3 of TOA SW CRF
• 0.3 of TOA Net CRF
• 0.3 Wm-2 climate reqmt (BAMS, Sept 2005)

High Accuracy Multi-Decadal Records
Critical Variability vs
Anthropogenic
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Tropical (20S - 20N) TOA Radiation
AnomaliesERBE/ScaRaB/CERES Comparisons
Best absolute accuracy of 0.5 to 2 insufficient
for climate anomalies Overlap is Critical
stability capability exceeds absolute accuracy
Wong et al., J. Climate, in press
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What do current instruments Provide?

• Goal of 0.3 SW and 0.5 LW stability very tough
  to achieve
• CERES nominal stability design is 0.5 per 6 year
  mission life
• Correction of RAP data transmission loss is 1
  SW in 4 years and was possible only because of
  independent crosstrack/RAP data
• AVHRR and geostationary imager visible channels
  several per year change. Constrained to 3-5
  using clear sky desert, ice.
• MODIS/MISR differ by 3 in absolute calibration
  and estimate stability at 2 per 6 years or
  better (using diffuser plates)
• SeaWIFS ocean color using monthly lunar views
  estimates stability constrained to 0.1 for
  annual mean, but only for dark targets (lunar
  reflectivity 5 to 10).
• For dark lunar targets need linearity of 0.1
  to transfer to much brighter scenes including
  clouds, snow, and desert.
• Current satellite instruments stress
  spatial/spectral resolution, not accuracy and
  stability of calibration. Detector linearity
  only a few .
• NPOESS VIIRS imager dropped lunar calibration
  (cost)
• Ocean color community cant use MODIS Terra
  worried about VIIRS.
• NPOESS weather priority cannot afford critical
  climate calibration requirements behind cost and
  schedule now.

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Satellite Climate Calibration Observatory

• Major problem for climate is achieving both
• sufficient global sampling (large regional
  variability, small global signals)
• sufficient calibration and especially stability
• no designed climate observing system currently
  exists.
• Current instruments focus on sampling first,
  calibration second
• Adding rigorous calibration sources and
  independence can double the size/cost of
  instruments
• Turn the problem around
• dont try to climate calibrate every satellite
  instrument
• dont try to sample the entire earth
• instead design instruments to be highly
  calibrated and stable transfer radiometers in
  orbit
• essentially provide a NIST quality calibration
  standard laboratory in orbit.
• design orbits, fields of view, pointing
  capabilities to optimize calibrating other
  instruments not sampling earths highly variable
  fields.
• much larger fields of view (50 to 100km) could
  be used leading to much smaller optics
  size/mass/power.

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Satellite Climate Calibration Observatory

• What would such an observatory look like?
• Precessing 67 degree inclined orbit
• Changes local sampling time by 24 hours every 3
  months
• Allows under-flight of all other spacecraft
  orbits leo, geo, etc
• Orbit period varies with altitude choose an
  altitude different than other satellites to allow
  matched time/location calibrations with all
  satellites for example 650 km.
• Varying local time assures that inter-calibration
  locations will vary from the equator to about 70
  degrees latitude and will cover a complete range
  of climate conditions.
• Two satellite calibration observatories at any
  time in orbit 6 hours of local sampling time
  apart, altitudes can differ (e.g. 650, 750km) to
  allow each to have different phasing of orbit
  synchronization with other satellites.
• Require /-5 minute simultaneity in orbit
  crossing locations same time/location/viewing
  angles. 10 of orbits (100 min period) will fill
  this criteria. Over long time periods this
  averages 1.4 calibrations per day with a low
  earth orbit spacecraft (e.g. sunsynch NPOESS) or
  more for geostationary.
• Can predict a week ahead when matched calibration
  orbit crossings will occur, what location, and
  what viewing angles.
• When one of the observatories or its instruments
  fail launch a replacement within 3 months. Use
  small Pegasus launch vehicles (instruments are
  small) and have spare spacecraft ready.

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Satellite Climate Calibration Observatory

• What types of instruments could be used for
  calibration standards?
• must be highly linear detectors (0.1) cavities,
  bolometers, etc
• must be capable of handling most of the solar and
  thermal infrared spectrum, including spectral
  resolution to match imagers and other
  spectrometers
• must be able to constrain total broadband energy
• field of view must be large enough to allow very
  accurate integration of other radiometers to
  match its fov nominally 100km
• field of view must be narrow enough to allow
  close matching of viewing zenith and azimuth
  angles to within /- 5 degrees/unbiased
• instruments and/or spacecraft must be able to
  control pointing accurately enough to achieve 98
  fov matching 2 km of 100 km fov. CERES is
  1km, MODIS is 100m.
• must have very accurate/stable independent
  calibration sources (e.g. deep cavity backbodies,
  lamps, solar viewing, lunar viewing)

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Satellite Climate Calibration Observatory

• Example instruments
• ERBS active cavities have demonstrated 0.1
  stability/decade, use solar constant checks every
  2 weeks.
• SORCE active cavities for solar irradiance, and
  prism spectrometer for spectral solar irradiance.
  Modify for earth viewing capability? Large fov?
  
• Truths instrument design for spectral solar?
• Anderson/Goody interferometer for 4 to 20mm
  (bolometer detectors, 100km fov, nadir only).
  Reach 50- 100mm water vapor greenhouse?
• Mlynczak FIRST Far-IR interferometer for 10 to
  100um (balloon test)
• Leonardo reflectivity spectrometer concept
  modify for calibration instead of angle/spatial
  sampling? 0.4 - 2.5mm.
• Lunar stability monitoring requires 1km fov to
  scan the roughly 6km lunar diameter (e.g.
  SeaWIFs). Also requires 0.1 linearity (dark
  target).
• In calibration mode, there is more dwell time for
  intercalibration when compared to normal
  scanning 10 to 100 times longer light gathering.
  
• Suggests
• 2 cavities (SW, Total) 500km fov
• IR spectrometer, 100km fov, dual deep cavity
  sources, 4 to 100mm wavelengths
• SW spectrometer, 100km fov, diffuser, solar views
• SW spectrometer, 1km fov/150km swath, lunar
  views, check 100km fov instrument

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Climate Calibration Observatory Summary

• Calibration first design linear, stable, full
  solar/ir spectra
• Intercalibration design for precessing
  orbit/large fov/pointing
• Launch on demand to reduce gap risk to lt 1.
• Two observatories allows independent calibration
  confirmation
• Provide a few hundred intercalibration samples
  for other instruments per year. 1 sigma noise in
  each sample 1. Annual mean lt0.1
• Allows a way to deal with uncertain NPOESS future
  calibration
• Allows calibration of geostationary
  imagers/sounders
• Allows calibration checks of international and
  U.S. missions
• CERES Rotating Azimuth plane scanner has
  demonstrated such intercalibration campaigns for
  precessing vs. sunsynchronous vs. geo orbits for
  CERES and GERB. Matches in time/space/angle
• Turns around our normal space mission design to a
  different paradigm to support climate change.
• For Climate Remote Sensing Calibration is the
  1st dimension.
• The other 8 are x, y, z, t, wavelength, s.
  zenith, v. zenith, v. azimuth angle.

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Examples that we are getting close

• Global Net Radiation and Ocean Heat Storage
  (In-situ/altimeter)

Wong et al. 2006 J.Climate, in press
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Examples that we are getting close
0.21 Wm-2
Shows consistent calibration stability at lt 0.3
Wm-2 per decade (95 conf) Unfortunately only
works for tropical mean ocean (nband vs bband
issues) Regional trends differ by 2 to -5
Wm-2/decade SeaWiFS vs CERES
Loeb et al. 2006 JGR, submitted
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CERES Shortwave TOA Reflected Flux Changes Ties
to Changing Cloud Fraction
Unscrambling climate signal cause and effect
requires complete parameter set at climate
accuracy. For e.g. for forcing/response
energetics radiation, aerosol, cloud, land,
snow/ice, temperature, humidity, precipitation
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Examples that we are getting close
Half of Anthrop Forcing of 0.6 Wm-2 /decade

• Given climate variability, 15 to 20 years is
  required to first detect climate trends at cloud
  feedback level with 90 confidence

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Earthshine, ISCCP, CERES 2000 to 2004
Climate accuracy requirements are poorly
understood by the community recent Earthshine 6
changes were published in Science, causing much
confusion
Loeb et al., AGU 2005
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ISCCP FD versus CERES 2000 to 2004
Tropical 30S-30N
Global 90S-90N
Meteorological satellite climate data is not
accurate or stable enough to determine decadal
trends, but very useful for regional studies.
Loeb et al., AGU 2005
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Amount of change for a factor of 6 in climate
model sensitivity (2K to 12K for doubling CO2)
Cloud, Radiation, Sea Ice variables very sensitive
Dynamics variables not very sensitive
Weather dynamics, Climate energetics Need
Climate Change OSSEs, Climate Obs. Reqmts
Murphy et al. Nature, 2004
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Conclusions

• The high confidence needed to be effective for
  climate policy critically needs
  calibration/stability/independent obs/independent
  analysis.
• IPCC AR4 preliminary conclusions
• aerosol indirect effect is forcing uncertainty,
• cloud feedback is dominant sensitivity
  uncertainty especially low cloud
• both require critical accuracy in SW cloud
  radiative forcing
• Climate Calibration Observatory concept can meet
  many of the ASIC3 requirements, but needs
  development and demonstration
• Near-term actions
• Keep SeaWiFS alive current source of lunar
  stability transfer
• Put Landsat/SPOT/etc on lunar stability scale
  with calibration manuevers
• Fill broadband gap by putting CERES FM-5 copy
  back on NPP (2009)
• Improve 80s/90s ISCCP and SRB data using ERBS
  active cavities as the poor mans climate
  calibration observatory for cloud/radiation
• Climate Calibration Observatory need phase A/B
  studies soon