1. Science Questions: Climate Benchmarking and On- Orbit SI Traceability CLARREO WORKSHOP Tuesday 21 October 2008 Jim Anderson, John Dykema, Stephen Leroy, Jon Gero, Hank Revercomb, David Tobin, Fred Best, Bill Collins, Andy Lacis, V. Ramaswamy, Bruce Wielicke, et al.

2. 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 the climate forcing variables on climate change

3. Science Driving the CLARREO Mission is Contained in Two Societal Objectives I. Societal Objective of establishing 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. II. Societal objective of the development of an operational climate forecast: The critical need for climate forecasts that are tested and trusted through a disciplined strategy using state-of-the-art observations with mathematically rigorous techniques to systematically improve those forecasts.

4. Science Questions I.Societal Objective of establishing 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. 1.Given the rapid increase in climate forcing from carbon release, how is the Earth’s climate system changing?

5. Global Energy Demand (Population) (Per Capita Income) = Units: joules (Energy demand per dollar of output) x x What drives the demand for global energy? 2005 0.4 zetta- joules of energy/yr 2050 1.0 zetta- joules of energy/yr

6. What is this.6 zettajoule of increased energy demand per year by 2050 equivalent to? Commissioning of 250 nuclear power plants per year for the next forty years. or The construction of 1000 large coal burning power plants per year for the next forty years.

7. Trajectory of Global Fossil Fuel Emissions Raupach et al. 2007, PNAS Observed 2000-2006 3.3% 2006 2005

8. How does energy flow within the climate system? Very large flow of energy cycles through the Earth-Atmosphere System. Small changes in escape of IR radiation passing through atmospheric blanket to space will dramatically affect energy (heat) flow into major reservoirs: ocean, land, ice, atmosphere. Energy flow per year

10. CLARREO: Why Now? The urgency for the CLARREO mission is a result of the rapidly growing societal challenge of current and future climate change: The urgent need to quantitatively define global climate change against SI traceable standards on-orbit and to systematically test and improve predictive capability of climate change, to develop intelligent plans to minimize it, and to plan methods to adapt to it. This urgency is built upon the growing realization in the climate science community of the critical need for higher-accuracy decadal change observations than currently exist.

11. Science Questions I.Societal Objective of establishing 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. 1.Given the rapid increase in climate forcing from carbon release, how is the Earth’s climate system changing? 2.Recognizing the impact on both scientific understanding and societal objectives resulting from the irrefutable, high accuracy, SI traceable Keeling CO 2 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?

12. A Metrologically Disciplined Analysis of Climate Observables Reveals a Small Number that are SI Traceable On-Orbit Absolute Spectrally Resolved Radiance Emitted from the Earth to Space: IR and SW Refractivity of the Atmosphere Observed by Radio Occultation Solar Irradiance

13. Distinction Between SI Traceable On-Orbit Benchmark and Quantities Derived from the Benchmarks Climate observables that are SI traceable on-orbit Absolute spectrally resolved radiance emitted from Earth to space Refractivity of the atmosphere observed by radio occultation Solar irradiance SI Traceable Benchmark Climate Observations Water Vapor Cloud Fraction Temperature Aerosols Lapse Rate Derived Quantities

14. Axiom 1: Within the context of climate, metrology and the physical sciences, confusing the distinction between accuracy, precision and “stability” is a deadly sin. Axiom 2: Within the context of climate and the metrology associated therewith, confusing the distinction between an on-orbit SI traceable observable and a retrieved quantity extracted therefrom is a deadly sin.

16. Climate Model Process Improvements Climate Process Observations (Airborne obs., A-train) Climate model process testing Improvements in subroutines incorporated in climate models Establish improvements needed in model dynamics, radiation, and chemistry Climate Benchmark Observations High Accuracy Climate Benchmark Observations (CLARREO) Quantitative determination of how Earth’s climate is changing SI traceable determination of instrument bias on-orbit High accuracy determination of climate forcing and response Extension of Keeling-quality climate record to on-orbit observables End-to-end test of forecast ability to calculate time series

17. Radiance Differences for Selected 4AT Model at Midlatitude

19. The CLARREO Paradigm Determination of the time dependent bias on-orbit Error in absolute temperature Error in on-axis emissivity Error introduced by changes in polarization Error introduced by scattered light Error introduced by change in optical performance Error introduced by changes in the temperature gradient of blackbody

20. Deconstructing the Equation Representing the Time Dependent Bias Determination On-Orbit Error in absolute temperature on-orbit Error in on-axis emissivity Error introduced by changes in polarization

21. Deconstructing the Equation Representing the Time Dependent Bias Determination On-Orbit Error introduced by scattered light Error introduced by changes in optical performance Error introduced by changed in the temperature gradient of blackbody

22. GPS Radio Occultation

23. Calibration: Double Differencing Hardy, K.R., G.A. Hajj, and E.R. Kursinski, 1994: Accuracies of atmospheric profiles obtained from GPS occultations. Int. J. Sat. Comm., 12, 463-473.

24. Distinction Between SI Traceable On-Orbit Benchmark and Quantities Derived from the Benchmarks Climate observables that are SI traceable on-orbit Absolute spectrally resolved radiance emitted from Earth to space Refractivity of the atmosphere observed by radio occultation Solar irradiance SI Traceable Benchmark Climate Observations Water Vapor Cloud Fraction Temperature Aerosols Lapse Rate Derived Quantities

25. Science Questions II.Societal objective of the 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. How accurately do climate forecast GCMs calculate the trend in longwave forcing by carbon dioxide, by nitrous oxide, by methane, by ozone, by halocarbons, etc.? How accurately do climate GCMs calculate the trend in longwave response of the atmosphere as conveyed in the spectrally resolved longwave radiation on continental scale? How accurately do climate GCMs calculate the trend in the shortwave radiative forcing by aerosols (aerosol direct effect), by land use change, by snow and ice? How accurately do climate GCMs calculate the major shortwave radiative feedback processes in the atmosphere that are largely responsible for the equilibrium climate sensitivity calculated by climate models?

26. Climate Model Process Improvements Climate Process Observations (Airborne obs., A-train) Climate model process testing Improvements in subroutines incorporated in climate models Establish improvements needed in model dynamics, radiation, and chemistry Climate Benchmark Observations High Accuracy Climate Benchmark Observations (CLARREO) Quantitative determination of how Earth’s climate is changing SI traceable determination of instrument bias on-orbit High accuracy determination of climate forcing and response Extension of Keeling-quality climate record to on-orbit observables End-to-end test of forecast ability to calculate time series

27. End-to- End Climate Forecast Testing High Accuracy Climate Benchmark Observations (CLARREO) End-to-end test of climate forecast decadal change Test of climate forecast feedbacks Test of climate forecast forcing and response Elimination of IPCC models that cannot correctly calculate trends, forcing and feedbacks

28. Testing Climate Models Response = Forcing  Sensitivity  1 = 1.7 w/m 2 -K(water vapor)  2 = –0.3 w/m 2 -K(lapse rate)  3 = 0.5 w/m 2 -K(clouds)  4 = 0.5 w/m 2 -K(surface albedo in cryosphere)

29. Information in Infrared Obtain part of feedbacks

30. CLARREO Science Questions Science Question (“Change over time = Decadal change) Climate Forcing CLARREO Science Impact CLARREO SI Traceable Observable CLARREO Implementation Approach 1. How is the anthropogenic greenhouse gas radiative forcing changing over time? How accurately is this forcing change represented in models? CriticalThermal IR Absolute spectrally resolved radiance (i) 2. How is solar irradiance changing over time? How accurately is this forcing change represented in models? CriticalTotal and spectral solar irradiance(i) 3. How is the reflected solar irradiance from Earth changing over time? How accurately is this forcing change represented in climate models? –Aerosol direct effect –Aerosol indirect effect –Land use CriticalAbsolute spectrally resolved radiance as a function of angle and polarization (ii) – (iii) Climate Feedbacks 4. What is the amplitude of the water vapor feedback? How accurately is it represented in climate models? CriticalAbsolute spectrally resolved IR radiance (i) 5. What is the amplitude of the temperature feedback? How accurately is it represented in climate models? CriticalGPS Absolute spectrally resolved IR radiance (i) 6. What is the amplitude of cloud feedback in the longwave component? How accurately is it represented in climate models? CriticalAbsolute spectrally resolved IR radiance (i) 7. What is the amplitude of the cloud feedback in the shortwave component? How accurately is it represented in climate models? CriticalAbsolute spectrally resolved SW radiance with polarization (ii)

31. CLARREO Science Questions Climate Response CLARREO Science Impact CLARREO SI Traceable Observable CLARREO Implementation Approach 8. How is the vertical temperature and water vapor structure in the atmosphere changing over time? How accurately do climate models predict the changes? CriticalAbsolute spectrally resolved IR radiance GPS refraction (i) 9. How are the cloud properties (fraction, optical depth, emissivity, height) changing over time as manifest in the IR? How accurately do climate models predict the changes? CriticalAbsolute spectrally resolved IR radiance GPS refraction (i) – (ii) 10. How are the cloud properties (fraction, optical depth, emissivity, height, temperature, phase, particle size) changing over time as manifest in the SW? How accurately do climate models predict the changes? CriticalAbsolute spectrally resolved SW radiance as a function of angle and polarization (ii) – (iii) 11. How are the amplitude and phase of diurnal cycles of Earth emitted IR radiance changing over time? How accurately do climate models predict the change? CriticalAbsolute spectrally resolved IR radiance GPS refractivity (i) 12. How are the amplitude and phase of diurnal cycles of Earth’s reflected absolute spectrally resolved shortwave radiance changing over time? How accurately do climate models predict the changes? CriticalAbsolute spectrally resolved SW radiance as a function of angle and polarization (ii) – (iii) 13. How is vegetation responding to climate change, including ocean color. How accurately do climate models predict the changes? ImportantSpectrally resolved SW radiance as a function of angle (ii)

32. The CLARREO Design Objectives in Shortwave Region Calibration against SI traceable standards on-orbit Identification of source of reflected solar irradiance Intercalibration of other SW instruments on-orbit

36. Stokes Parameters: Quantitative Foundation Defining Electromagnetic Radiation Stokes parameters are both necessary and sufficient to link on-orbit observations to an SI traceable standard

37. Measurement of I, Q, u, V Requires within the CLARREO paradigm 1.Absolute on-orbit calibration of I(λ,ψ,ε) 2.Ability to define the SRF of the instrument(s) on-orbit 3.Ability to rotate the plane of polarization of the spectrometers 4.Ability to vary the along track scan angle of the observations Wavelength Plane of Polarization Retardation

38. Stokes Parameters Define the Degree of Polarization and the Degree of Linear Polarization Degree of Polarization: Degree of Linear Polarization: For unpolarized Light: Light emitted from the sun is unpolarized Thermal emission in the IR is unpolarized

39. The CLARREO Design Objectives in Shortwave Region Calibration against SI traceable standards on-orbit Identification of source of reflected solar irradiance Intercalibration of other SW instruments on-orbit

40. CLARREO: Why Now? The timing of the CLARREO mission (why now?) is a result of recent advances in a wide range of scientific, metrology, and technological research. These recent advances include: Development of a new generation of optical subsystems in the thermal infrared which, when taken together, provide SI traceable on-orbit accuracies (absolute) to 50 mK. Evolution of the sophistication in GPS design and retrievals such that accuracies (absolute) of 0.1 K with a vertical resolution of 0.1 km is achieved with global soundings. New methods at national physics laboratories developed to increase the accuracy of solar wavelength standards by an order of magnitude. An example is the SIRCUS (Spectral Irradiance and Radiance Calibrations with Uniform Sources) facility at NIST and its portable version. Greatly increased experience with more accurate high spectral resolution mid-infrared spectrometers and interferometers for temperature, water vapor, and cloud sounding (AIRS, IASI, CrIS spaceborne instruments, as well as AERI, NAST-I, HIS, and Intesa ground and airborne instruments. The first successful Far Infrared Interferometer flights on a high-altitude balloon (FIRST) Greatly improved methods and understanding of how to accurately intercalibrate instruments in orbit, including interferometers, imagers, and broadband radiation budget instruments Demonstrations of the value of polarization measurements of aerosol properties and the ability to build such instruments at high accuracy (POLDER, APS) Greatly improved understanding of the angle/space/time variability of radiative fluxes from the new CERES analysis that combines up to 11 instruments on 7 spacecraft into an integrated radiative flux climate data record

41. CLARREO: Why Now? The timing of the CLARREO mission (why now?) is a result of recent advances in a wide range of scientific, metrology, and technological research. These recent advances include: A clearer understanding of the value of decadal-change observations at high accuracy in providing the critical testing ground for the accuracy of climate model predictions A clearer understanding of the level of uncertainty in climate forcings and feedbacks, Improved accuracy of infrared blackbody sources using phase change temperature measurements as part of highly accurate deep well blackbodies. Improved accuracy of spaceborne spectral and total solar irradiance using active cavity absolute detectors (e.g., SORCE) Factor of 1000 improved sensitivity of active cavity detectors through cryogenic cooling (including mechanical coolers) to low temperatures. These have been in use at standard labs such as NIST and in vacuum ground calibration facilities such as that for CERES

42. End

46. Recognizing the impact on both scientific understanding and societal objectives resulting from the irrefutable, high accuracy, SI traceable Keeling CO 2 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? How is the temperature structure of the atmosphere changing on spatial and temporal scales relevant to climate? How is the specific humidity changing on defined pressure surfaces on spatial and temporal scales relevant to climate? How is cloudtop height changing on spatial and temporal scales relevant to climate? How is cloud liquid water path changing on spatial and temporal scales relevant to climate? How is cloud fraction changing on spatial and temporal scales relevant to climate? How are the amplitude and phase of the diurnal cycle in temperature, water vapor, and clouds changing? How rapidly is the troposphere expanding? How are the tropopause height and temperature changing? How is the thickness of the planetary boundary layer changing? How is the width of the Hadley cell changing? How is the aerosol direct effect changing on spatial and temporal scales relevant to climate? How is cloud nadir reflectivity changing on spatial and temporal scales relevant to climate? How is surface snow and ice changing on spatial scales relevant to climate as a function of season? How is surface albedo changing due to changes in land use?

47. Climate is forced by the long-term balance between (1) the solar irradiance absorbed by the earth-ocean-atmosphere system, and (2) the infrared (IR) radiation exchanged within that system and then emitted to space. What are the changes in the spatial, spectral, and temporal fluxes of radiation at the top-of-the-atmosphere (TOA)? What is the trend in longwave forcing by carbon dioxide, by nitrous oxide, by methane, by ozone, by halocarbons, etc.? What is the response of the atmosphere as conveyed in the spectrally resolved longwave radiation on continental scales? How is surface-to-space longwave radiation changing? How large is the lower tropospheric water vapor-longwave feedback? How large is the upper tropospheric water vapor-longwave feedback? How large is the lapse rate feedback? How large is the low cloud-longwave feedback? How large is the high cloud-longwave feedback? What is the response of the atmosphere as conveyed in the shortwave spectrum on continental scales? What is the trend in the shortwave radiative forcing by aerosols (aerosol direct effect)? What is the trend in the shortwave radiative forcing by land use change? What is the trend in shortwave radiative forcing by snow and ice? How large is the cloud-shortwave feedback? How large is the aerosol indirect effect?

48. How accurately do state-of-the-art climate GCMs calculate the trend in longwave response of the atmosphere as conveyed in the spectrally resolved longwave radiation on continental scales? Specifically, how accurately do climate forecast GCMs calculate: Absolute magnitude and trends in surface-to-space longwave radiation? Absolute magnitude in the lower tropospheric water vapor-longwave feedback? Absolute magnitude in the upper tropospheric water vapor-longwave feedback? Absolute magnitude in the lapse rate feedback? Absolute magnitude in the low cloud-longwave feedback? Absolute magnitude in the high cloud-longwave feedback?

49. How accurately do state-of-the-art climate GCMs calculate the major shortwave radiative feedback processes n the atmosphere that are largely responsible for the equilibrium climate sensitivity calculated by climate models? Specifically, how accurately do state-of-the-art GCMs calculate: Cloud-shortwave feedback? Aerosol indirect effect?

50. CLARREO Team NASA Langley Research Center: Dave Young University of California, Berkeley Harvard University NIST Jet Propulsion Laboratory University of Wisconsin Goddard Institute for Space Science Goddard Space Flight Center Geophysical Fluid Dynamics Laboratory University of Colorado-LASP

51. Technical Presentations Jonathan Gero, Harvard University: Progress in On-Orbit SI-traceable Radiance Measurements for CLARREO –Tuesday @ 9:20 Sergey Mekhontsev, NIST: Spectral Characterization of Infrared Radiometers and Imagers –Tuesday @ 10:00 Tom Stone, US Geological Survey: Calibrated Stellar Data Base of the USGS Lunar Calibration Program –Tuesday @ 11:55 John Dykema, Harvard University: On-Orbit Calibration Knowledge and Program Objectives for CLARREO –Tuesday @ 4:15 Greg Kopp, LASP: CLARREO Mission Visible and Near-Infrared Radiometry Studies –Tuesday @ 4:55

52. Distinction Between SI Traceable On-Orbit Benchmark and Quantities Derived from the Benchmarks Climate observables that are SI traceable on-orbit Absolute spectrally resolved radiance emitted from Earth to space Refractivity of the atmosphere observed by radio occultation Solar irradiance SI Traceable Benchmark Climate Observations

53. Surface Air Temperature

54. GPS Radio Occultation (2) Orbit determination and clock correction, GPS and LEO: dL/dt Diffraction (and multipath) inversion: ε(p) Inversion for refractivity: N(r) Kursinski, E.R., G.A. Hajj, J.T. Schofield, R.P. Linfield, and K.R. Hardy, 1997: Observing Earth’s atmosphere with radio occultation measurements using the Global Positioning System. J. Geophys. Res., 102, 23429-23465. Hajj, G.A., E.R. Kursinski, W.I. Bertiger, L.J. Romans, and S.S. Leroy, 2002: A technical description of atmospheric sounding by GPS occultation. J. Atmos. Solar-Terr. Phys., 64, 451-469. Gorbunov, M.E., H.H. Benzon, A.S. Jensen, M.S. Lohmann, and A.S. Nielsen, 2004: Comparative analysis of radio occultation processing approaches based on Fourier integral operators. Radio Sci., 39, doi:10.1029/2003RS002916.

55. GPS Radio Occultation (3) Refractivity “Dry” pressure Geopotential height

56. Science Questions II.Societal objective of the 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. 3. How accurately do climate forecast GCMs calculate the trend in longwave forcing by carbon dioxide, by nitrous oxide, by methane, by ozone, by halocarbons, etc.?