CLARREO Workshop: Summary and Next Steps

1. CLARREO Workshop:Summary and Next StepsDavid F. YoungNASA Langley Research CenterCLARREO Mission Study Lead CLARREO Science Workshop 21-23 October 2008 Washington, DC

2. Outline • Summary of Workshop Sessions • What Next? • Science Questions • Wrap-up discussion

3. Important Example of an SI Traceable Data Record Phillies 3 Rays 2 Philadelphia Phillies Games Won vs Year

4. Review of Sessions

5. Workshop Sessions • Introduction to CLARREO Chair: David Young • Science Questions: Climate Benchmarking and S.I. Traceability Chair: Jim Anderson • Science Questions: Climate Prediction and Climate Model Testing Chair: Bill Collins • Sampling Chair: Daniel Kirk-Davidoff • Applied S.I. Traceability (and Instrument Incubator Proposals) Chair: John Dykema • Inter-calibration of Operational Instruments Using CLARREO Chair: Bruce Wielicki • The Way Forward Chair: David Young

6. Summary of Introduction Session • Steve Volz and Jack Kaye • NASA HQ perspectives on implementation of the Decadal Survey missions • Expectations for the CLARREO team • David Young • Set the stage for the Workshop • John Bates • NOAA is working actively on continuity of the climate observation system • NOAA is anticipating the benefits of CLARREO

7. II: Science Questions: Climate Benchmarking and On-Orbit SI Traceability • The key role played by optical radiation and climate. • Challenge: Lack of accurate models and lack of accurate observations. • Climate measurements require a new strategy linking to SI traceability on-orbit that establish an unbroken chain with uncertainties tested for systematic errors. • These benchmark observations must gain the trust of the scientific and public policy communities: stark contrast between Keeling and ground based measurements. • Spectral radiances can be directly tied to SI traceable units: when used with ancillary data and/or models to derive climate variables, SI traceability broken. • Quality of traceability claim runs from no traceability (level 0) through imagery satellites (level 1-2), metorological satellites (level 3), research satellites (3-4) to climate benchmark satellites (level 5) • When claim is made that sensor is “stable” it means accuracy/traceability is secondary. • The National Measurement Laboratory model for traceability • NIST optical measurements traceable through the electrical watt, aperature measurements through the meter, radiance through both source-based and detector based approaches: SIRCUS. • Strategy of constant and continuous intercomparison with international standards. • CLARREO objectives and NIST strategy tightly linked.

8. II: Science Questions: Climate Benchmarking and On-Orbit SI Traceability • The CLARREO Imperative: If the climate observable is not SI traceable it does not fall within the CLARREO paradigm • Science driving the CLARREO mission is contained within two societal objectives: (1) Establishing Global Climate Benchmarks and (2) Development of an Operational Climate Forecast • Given the rapid increase in climate forcing from carbon release, how is the Earth’s climate system changing? • Tracking the dramatic increase in primary energy generation. • Carbon release from fossil fuel combustion reached 8.4 GtC/yr in 2006 headed for 10 GtC/yr in 2009. • Rapid melting of Arctic Ice requires just 0.1 ZJ/yr of the 6000ZJ/yr cycling in climate system. Axiom: It is the flow of heat not global warming that carries the critical message. • CLARREO: Why Now? • Critical distinction between SI traceable on-orbit benchmark and quantities derived from, or retrieved from, those observations. Axiom 1 and Axiom 2. • Distinction between CLARREO benchmarking and process studies; between CLARREO climate forecast testing and process studies. • CLARREO paradigm: determination of each term in the time dependent bias equation with a specific subsystem on-orbit. • Why GPS is SI traceable on-orbit and why it is a powerful complement to absolute spectrally resolved IR radiance. • Forcings and Feedbacks: The mathematical formulation and the specific science questions associated therewith • Objective in the SW: The critical role played by the Stokes parameters • Technical Advances behind CLARREO: Why Now.

9. II: Science Questions: Climate Benchmarking and On-Orbit SI Traceability • CLARREO is a NASA new start based on NRC Decadal Survey based on science/societal objectives prioritization and backed by ASIC3 technical analysis. • Strong and broad teaming of NASA centers, agencies, and university involvement • The unique contributions that CLARREO adds for benchmarking and end-to-end model testing that is distinct from that of process studies. • Why we need CLARREO: Serious gaps in accuracy capability of existing systems - broadband has very limited information content and is not SI traceable. OLR insensitive to trends in T surface, atmosphereic T, WV, C. • Filter radiometer sounders and imagers: very limited accuracy even IR. • New high resolution IR sounders: not designed for nor optimized for determination of unequivocal decadal trend measurements. Many examples. • Basic tenants and new paradigms for CLARREO: High information content, very high accuracy (absolute) with accuracy proven on-orbit, commitment to long-term records of climate for societal objectives. • Analysis of the power of using direct observable SI traceable radiance: Multiple examples. • Analysis of key advances needed from dedicated climate system: CLARREO • Powerful link between absoluted spectrally resolved radiance in IR and GPS RO. • High level CLARREO requirements: Spectral coverage and resolution, spatial footprint and angular sampling, temporal resolution and sampling. • Analysis of statistical recovery and footprint size in many domains globally. • Analysis of annual mean spectral 25 year trends: CLARREO does not need cloud clearing - it is a critical spectral component that is an integral part of the climate record. • Orbits: the combination of spatial and temporal sampling to minimize bias from harmonics of the diurnal variation requires three true 90 degree polar orbits. • Requirements of subsystems for SI traceability on orbit: absolute temperature phase transition cells, direct emissivity measurements, polarization, linearity, etc.

10. Science Questions: Climate Prediction and Climate Model Testing • OSSE Team: Climate Model Observing System Simulation Experiments • OSSE uses climate projections to emulate CLARREO spectra. • Can cloud responses be separated from other signals? • Does OSSE bound significance of detection and attribution? • Should team conduct exploratory SW LBL calculations to interpret OSSE? • Stephen Leroy: Testing Models with CLARREO: Feedbacks and Sensitivity • Trends in GPS radio occultation useful to monitor surface temperature. • Trends in outgoing LW spectrum constrain LW forcings and feedbacks. • Optimization in space is necessary to reduce detection times. • Work in progress includes simulations in cloudy skies and shortwave trends. • Mike Mishchenko: Constraining climate models with polarized radiances • Current knowledge of AOT and aerosol microphysical are unsatisfactory. • Polarimetric measurements can be accurately and stably calibrated on orbit. • Polarimetry is useful to characterize aerosols and cloud properties. • What are trade-offs implied by swap of polarimeter for spectrometer?

11. Science Questions: Climate Prediction and Climate Model Testing • Peter Pilewskie: CLARREO Visible and Near-Infrared Studies • Water vapor feedback drives SW accuracy requirement of about 0.2-0.3% • SW information content is invariant for resolutions between about 5-20 nm. • PCA of SCHIAMACY show clouds/water vapor, vegetation, and Rayleigh • Other spectral decomposition methods may be more suitable than PCA • Cross-calibration issues lead to other spectral resolution • V. Ramaswamy: Radiation spectra at TOA and climate diagnoses • Methods to measure sensitivity of spectral outgoing longwave radiation • Outgoing longwave spectra are useful tests of climate system models • Infrared spectral signatures of climate change: emergence of H2O? • Possibilities of further climate information: Temperature stratification? • Kevin Bowman: Observational constraints on feedbacks • Combination of far-IR, IR, and visible spectra provides strong constraints on the radiative response of water in its 3 phases to anthropogenic forcing. • What are implications of FOV on the synergy of the spectral regions? • Could spectral combination capture climate signals from boundary layer?

12. III: Sampling • Bob Knuteson showed that subsampling of AIRS data along the satellite ground track at a range of footprint sizes produced very similar means and distributions of brightness temperatures for a range of frequencies. • Alex Ruzmaikin reviewed the statistical treatment of sampling errors, pointing out that the error of a mean depends on the standard deviation of the sampled data, the number of samples (including a negative exponent whose size between 0 and 1 depends on the autocorrelation of the sampled data), and a factor, also dependent on n, that determines how closely the sampled data is expected to come to a normal distribution. He showed that for brightness temperature distributions typical of tropical regions, approximately 1 year is needed for a single satellite to reduce random sampling error to 0.1 K over zonal mean bands. • Dan Kirk-Davidoff presented results from simulations of CLARREO sampling using proxy data from an archive of 10 micron brightness temperatures assembled from a suite of geostationary and polar orbiting satellites, and from modeled multispectral radiances derived from a GFDL coupled climate model run. He discussed both bias due to aliasing of observed variability by periodic observations and sampling errors due to random variablility, and showed that a single precessing orbiter is capable of producing means with an one-sigma accuracy of 0.1 K for zonal means, and at better than 0.3 K accuracy for 15 by 30 degree grid squares.

13. III: Sampling • Dave Doelling presented a study of ERBE LW and SW data used to scale GOES data, showing that variability in the diurnal cycle of spectrally averaged radiances was a relatively small source of error in sun-synchronously sampled data, especially when averaged globally. • Zhonghai Jin presented a study demonstrating the capacity of a solar irradiance instrument to detect some candidate climate trends in global and regional trends. Radiance data were simulated using aerosol and cloud properties from several retrieved data sets. • The discussions session following the talks focused on several points that arose in the talks and questions. Highlights included: the costs and benefits of off-nadir sampling from CLARREO, the interaction of spectral and spatial resolution in determining optimal footprint size, and on the need to quickly determine the minimum number of satellites required to answer the CLARREO science questions.

14. IV: Applied SI-Traceability • Relevant parts of CLARREO paradigm is essential information for decadal climate and SI traceability • IIP activities are pursuing technological developments to obtain new information (far IR), trace LW and SW to SI/NIST • UW/Harvard IIP developing technology for tracing blackbodies to SI on-orbit and interferometers to demonstrate calibration concept • Diffuse UW/Harvard cavity design will see performance decrease in far IR beyond 50 mm • LaRC IIP developing far IR blackbodies, detectors, beamsplitters • Useful synergy with CSA far IR mission under consideration?

15. IV: Applied SI-Traceability • LASP developing SW sensor capable of Earth observation and solar observation via attenuation by 10-5 • Combination of apertures, integration time, filters • Traceability to solar versus lunar preferable due to better spectral knowledge • Polarimetry: key question is quantifying relevant information obtainable from polarimetry (aerosols, land surface properties) versus radiometry (water vapor, molecular features); complementary information on clouds? • Aerosols by radiometry perhaps optimal in UV, requiring resolution << 10 nm • What polarimetric capabilities will be provided by other missions? • GPS-RO currently operational, data extend back 7 years through SAC-C, CHAMP • Current status of RO-Trends indicates COSMIC meeting CLARREO goals for zg>5 km; critical refraction limiting factor • International comparison of GPS-RO

16. TRUTHS: Traceable Radiometry Underpinning Terrestrial- and Helio- Studies • Satellite based mission to: • make traceable measurements of solar radiation incident on, and reflected from, the Earth • transfer its unprecedented calibration accuracy to other satellite-based EO instruments through the calibration of reference targets such as the Sun, Moon and the Earth’s deserts • Supporting measurements of land processes, ocean colour, Earth radiation budget, atmospheric chemistry and aerosol distribution - Wide spectrum (380 to 2500 nm) - Spatial resolution ~ 25 to 100 m (TBD) - Spectral radiance uncertainty <0.3% (using novel in-flight calibration system directly traceable to SI) Nigel Fox National Physical Laboratory

17. TRUTHS key instrumentation Core calibration unit:- Cryogenic Solar Absolute Radiometer (CSAR) - Primary standard - Spectral Calibration Source (SCS) - spectral range to suit - Filter Radiometers (FR) - number and spectral range to suit - Ground + atmosphere radiance (single pixel) Operational Instruments: - Earth imager - hyper-spectral (number of options) - Cryogenic Solar Absolute Radiometer (CSAR) - Total Solar Irradiance - Solar Spectral Irradiance Monitor (SSIM) - Solar spectral irradiance

18. Key instrument status/development Most TRUTHS instrumentation can be selected from existing instruments (or those under development) Principle instrument is CSAR – “primary standard” - Principle well known demonstrated in Lab for >20yrs - Now under development for TRUTHS and ground based deployment to replace WRR at Davos - Design driver is space flight (and TRUTHS requirements) - Instrument to have necessary redundancy (multi-cavity - mass, mechanical isolation, thermal capacity all based on needs of space and Astrium space cooler (much easier for ground application alone) - primary interface also Astrium cooler (with interface to ground cooler) - Cavities for both TSI (high power) and spectral response (low power)

19. CSAR: status • Preliminary design now complete based on models and FE analysis • Optical, • Thermal • Geometric • mechanical • Baseline design has ambient temperature limiting aperture at front of CSAR • Engineering drawings of prototype to be complete (Dec 08) • Prototype cavities currently being coated with NiP black • Prototype instrument for testing (summer 09) • Operational CSAR (ground, WRR DAVOS ) and engineering model (TRUTHS) spring 2010

20. TRUTHS mission status • - UK funding agencies, NERC, BNSC, still express interest but no commitment. • Project visible to senior UK political figures (science minister) (although personnel changed two weeks ago. • Discussions started with SSTL (Surrey Satellite Technology Ltd) regards collaboration and “mission of opportunity” • TRUTHS and CLARREO visible to, and encouraged to collaborate from CEOS • Interest in climate issues and ECVs increasing within Europe and UK likely to become host to a new ESA facility for “climate studies” SSTL platform capabilities: - Payload ~ 200 Kg - pointing accuracy = 0.04° - Pointing Knowledge = 0.001°

21. V. Intercalibration Using CLARREO

22. What Next?

23. √ √ √- √ Workshop Goals • Discuss and refine the CLARREO science objectives • Present results from on-going science trade studies for community comment • Define and refine the links between the identified science objectives and the measurement requirements • Present CLARREO-related Instrument Incubator Proposal Selections • Identify requirements for technological development to enable mission success • Identify studies needed to further the readiness of the CLARREO mission.

24. Tall Poles / Open Questions • Science Questions finalization and prioritization • Clearly state the unique aspect of CLARREO relative to the existing and planned climate observing system • Answering key questions • Sampling • Define accuracy goals based on global, zonal, or regional means • Identify sampling studies at selected orbits • Investigate sampling benefits of swath data • Consider Salby asynoptic theory • Perform SW-specific studies • Solar portion of CLARREO • What constitutes a reflected solar benchmark? • Criticality must be clear in science objectives (Collins) • Polarization vs. radiance • What is the actual accuracy goal? • Demonstration of Intercalibration in the solar • When do OSSE results come in?

25. How do we get there? • Continue telecons • Identify and support studies focused on identified tall poles • Science Requirements • Using input from this workshop the team will produce a final version of the Science Objectives document by November 30 • Release for public comment • Develop draft Level 1 requirements with some basic trades: Feb • Feb: Develop several mission concepts based on these requirements/trades • March: Produce initial cost scenarios for assistance in cost/science prioritization at April team meeting • April team meeting for agreement on Level 1 requirements • Concept to take to MCR: this is not the “final” CLARREO concept but should have a confidence of ~ 80%. Refinement of last 20% will occur through Phase A following MCR. • Mission studies will continue through 2008 and continue in 2009.

26. Science Questions

27. Defining CLARREO • NASA has formed a team to complete Pre-Phase A studies to define the CLARREO mission • The study plan represents an integrated strategy that engages climate scientists, modelers, satellite instrument teams and calibration experts from: • NASA LaRC, GSFC, and JPL • U.C. Berkeley / GISS / GFDL • Harvard University • University of Wisconsin-Madison • Laboratory for Atmospheric and Space Physics • Contributing, but not funded: • National Institute of Standards and Technology • Begin by defining the societal objectives and key science questions to be addressed by CLARREO

28. CLARREO Societal Objectives • Establishment of a climate benchmark: The essential responsibility to present and future generations to put in place a benchmark climate record, global in its extent, accurate in perpetuity, tested against independent strategies that reveal systematic errors, and pinned to international standards on-orbit. • Development of an operational climate forecast that is tested and trusted through a disciplined strategy using state-of-the-art observations with mathematically rigorous techniques to systematically improve those forecasts.

29. CLARREO Imperative • Initiate an unprecedented, high accuracy record of climate change that is tested, trusted and necessary to provide sound policy decisions. • Initiate a record of direct observables with the high accuracy and information content necessary to detect long term climate change trends and to test and systematically improve climate predictions. • Observe the SI traceable spectrally resolved radiance and atmospheric refractivity with the accuracy and sampling required to assess and predict the impact of changes in climate forcing variables on climate change.

30. CLARREO Science Questions • Given the rapid increase in climate forcing from carbon release, how is the Earth痴 climate system changing? • Recognizing the impact on both scientific understanding and societal objectives resulting from the irrefutable, high accuracy, SI traceable Keeling CO2 record, what measurements obtained from space would constitute an analogous high accuracy, SI traceable climate record defining the global response of the climate system to the anthropogenic and natural forcing?

31. How CLARREO Fits In

32. CLARREO Science Questions

33. Draft CLARREO Science Questions:Climate Forcing

34. Draft CLARREO Science Questions:Climate Response

35. Draft CLARREO Science Questions:Climate Feedbacks and Sensitivity

36. Wrap-up

37. Thank You Thanks See you at the Fall AGU Session Title: SI-Traceable Climate Measurements From Space: Requirements, Methods, and Accuracies • Oral session: Wednesday, Dec 17, 8:00-12:20 pm • Poster session: Tuesday, Dec 16, 13:40-18:00 pm

38. Backups

39. Discussion Points Sampling • The sampling rate requirement for accurate measurement increase as the length of the averaging period decreases, and as the statistical order of the measurement increases. How can we most clearly and concisely express the trade-off between the number of CLARREO orbiters and the attainment of CLARREO mission science goals? • What metrics of CLARREO science value should be used to determine the optimal field of view for the IR and visible instrument, and what weight should they be given? • How does the additional variable of solar zenith angle affect the sampling problem for the creation of benchmark observations of solar reflectance? Applied S.I. Traceability • What further technical advances are necessary to make each IIP flight worthy? • What systematic errors are known for IR, SW and how do we quantify them?

40. Discussion Points Inter-calibration of Operational Instruments • What spectral properties (e.g. coverage, resolution, sampling) are required of CLARREO for accurate intercalibration of operational IR imagers and sounders, solar and IR imagers, and broadband instruments like CERES? • What combination of CLARREO instrument noise performance and footprint size is required of CLARREO for accurate IR and solar reflected intercalibration? • What is the right time interval for calibration at climate accuracy? • Can we detect and correct spectral changes from in orbit optics contamination? • What is the requirement for in-situ/aircraft validation of CLARREO itself?

41. Suggested studies • Look at the combination of all spectral regions • Look at Line by Line to narrow focus on particular SW regions • Look at spectral resolution requirement for intercalibration • Sampling • Get Dan better data • Sampling studies at selected orbits • Look at swath • Salby asynoptic theory • Global vs regional? • SW study? • SCIAMACHY / MODIS comparison