1. Langley Research Center / Atmospheric Sciences Directorate Climate Calibration Observatory Roadmap/Decadal Survey Mission Concept Bruce 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) Francesco 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)

2. Langley Research Center / Atmospheric Sciences Directorate 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/temperature 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.

3. Langley Research Center / Atmospheric Sciences Directorate Tropical (20S - 20N) TOA Radiation Anomalies: Observations 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 0.5% of TOA LW CRF 0.3% of TOA SW CRF 0.3% of TOA SW CRF 0.3% of TOA Net CRF 0.3% of TOA Net CRF - 0.3 Wm -2 climate reqmt (BAMS, Sept 2005) High Accuracy Multi-Decadal Records Critical: High Accuracy Multi-Decadal Records Critical: Variability vs Anthropogenic Variability vs Anthropogenic

4. Langley Research Center / Atmospheric Sciences Directorate Tropical (20S - 20N) TOA Radiation Anomalies: ERBE/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

5. Langley Research Center / Atmospheric Sciences Directorate 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 can’t use MODIS Terra: worried about VIIRS. NPOESS weather priority cannot afford critical climate calibration requirements: behind cost and schedule now.

6. Langley Research Center / Atmospheric Sciences Directorate 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: –don’t try to climate calibrate every satellite instrument –don’t 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 earth’s highly variable fields. –much larger fields of view (~50 to 100km) could be used leading to much smaller optics size/mass/power.

7. Langley Research Center / Atmospheric Sciences Directorate 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.

8. Langley Research Center / Atmospheric Sciences Directorate 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)

9. Langley Research Center / Atmospheric Sciences Directorate 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 20  m (bolometer detectors, 100km fov, nadir only). Reach 50- 100  m 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 - 2.5  m. –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 100  m wavelengths SW spectrometer, 100km fov, diffuser, solar views SW spectrometer, 1km fov/150km swath, lunar views, check 100km fov instrument

10. Langley Research Center / Atmospheric Sciences Directorate 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 < 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 <0.1% 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.

11. Langley Research Center / Atmospheric Sciences Directorate Examples that we are getting close Global Net Radiation and Ocean Heat Storage (In-situ/altimeter) Wong et al. 2006 J.Climate, in press

12. Langley Research Center / Atmospheric Sciences Directorate Examples that we are getting close Shows consistent calibration stability at < 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 0.21 Wm -2

13. Langley Research Center / Atmospheric Sciences Directorate 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

14. Langley Research Center / Atmospheric Sciences Directorate Examples that we are getting close Given climate variability, 15 to 20 years is required to first detect climate trends at cloud feedback level with 90% confidence Half of Anthrop Forcing of 0.6 Wm -2 /decade

15. Earthshine, ISCCP, CERES: 2000 to 2004 Loeb et al., AGU 2005 Climate accuracy requirements are poorly understood by the community: recent Earthshine 6% changes were published in Science, causing much confusion

16. ISCCP FD versus CERES: 2000 to 2004 Loeb et al., AGU 2005 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.

17. Langley Research Center / Atmospheric Sciences Directorate Amount of change for a factor of 6 in climate model sensitivity (2K to 12K for doubling CO 2 ) Murphy et al. Nature, 2004 Weather = dynamics, Climate = energetics Need Climate Change OSSEs, Climate Obs. Reqmts Dynamics variables not very sensitive Cloud, Radiation, Sea Ice variables very sensitive

18. Langley Research Center / Atmospheric Sciences Directorate 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 ASIC^3 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