Science Questions: Climate Benchmarking and On- Orbit SI Traceability CLARREO WORKSHOP Tuesday 21 October 2008 Jim Anderson, John Dykema, Stephen Leroy,

Science Questions: Climate Benchmarking and On-Orbit SI Traceability

CLARREO WORKSHOPTuesday 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.

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

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.

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?

Global Energy

Demand

(Population)

(Per Capita Income)

=

Units: joules

(Energy demand per

dollar of output)

x

x

What drives the demand for global energy?

20050.4 zetta-

joules of energy/yr

20501.0 zetta-joules of energy/yr

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.

Trajectory of Global Fossil Fuel Emissions

Raupach et al. 2007, PNAS

Recent emissions

1990 1995 2000 2005 2010

CO

2 E

mis

sions

(GtC

y-1)

5

6

7

8

9

10Actual emissions: CDIACActual emissions: EIA450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

1850 1900 1950 2000 2050 2100C

O2 E

mis

sions

(GtC

y-1)

0

5

10

15

20

25

30Actual emissions: CDIAC450ppm stabilisation650ppm stabilisationA1FI A1B A1T A2 B1 B2

Observed

2000-2006 3.3%

2006

2005

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

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.

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 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?

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

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 S

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Water Vapor Cloud Fraction

Temperature AerosolsLapse Rate

Der

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Qua

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es

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.

Testing for human influence

Testing climate models











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 forecastability to calculate time series

Radiance Differences for Selected 4AT Model at Midlatitude

The CLARREO ParadigmDetermination of the time dependent bias on-orbit

Reported True BB BB( ) [ ] [ ] B BB t I I dT dT

BB

B Td XTX

OL S PS

B B BdP dR dOP R O

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

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

BBB dTT

BBB d

OLB dPP

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

SS

B dRR

PB dOO

BB

B Td XTX

GPS Radio Occultation

GPS GPS LEO LEOcos cosdL

v vdt

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.




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Water Vapor Cloud Fraction

Temperature AerosolsLapse Rate

Der

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Qua

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es

Science QuestionsII. 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?

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 forecastability to calculate time series

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

Testing Climate Models

1

LW SWrad i i

i i

T F

Response = Forcing Sensitivity

RAD

RAD

4

3RAD

4

ii

i

F T

F

F T

F T T

dxF

x dT

Planck response to radiative forcing

Stefan -Boltzmann

1 = 1.7 w/m2-K (water vapor)

2 = –0.3 w/m2-K (lapse rate)

3 = 0.5 w/m2-K (clouds)

4 = 0.5 w/m2-K (surface albedo in cryosphere)

Information in Infrared

Obtain part of feedbacks

1

ii

i

dxF dT

x dt dt

CLARREO Science Questions

Science Question (“Change over time = Decadal change)

Climate ForcingCLARREO

Science ImpactCLARREO

SI Traceable ObservableCLARREO

Implementation Approach

1. How is the anthropogenic greenhouse gas radiative forcing changing over time? How accurately is this forcing change represented in models?

Critical Thermal IR Absolute spectrally resolved radiance

(i)

2. How is solar irradiance changing over time? How accurately is this forcing change represented in models?

Critical Total 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

Critical Absolute 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?

Critical Absolute spectrally resolved IR radiance

(i)

5. What is the amplitude of the temperature feedback? How accurately is it represented in climate models?

Critical GPS 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?


(i)

7. What is the amplitude of the cloud feedback in the shortwave component? How accurately is it represented in climate models?

Critical Absolute spectrally resolved SW radiance with polarization

(ii)

CLARREO Science Questions

Climate ResponseCLARREO

Science ImpactCLARREO

SI Traceable ObservableCLARREO

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?


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?


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?

Critical Absolute 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?


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?

Critical Absolute 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?

Important Spectrally resolved SW radiance as a function of angle

(ii)

The CLARREO Design Objectivesin Shortwave Region

Calibration against SI traceable standards on-orbit

Identification of source of reflected solar irradiance

Intercalibration of other SW instruments on-orbit

Stokes Parameters: Quantitative FoundationDefining Electromagnetic Radiation

Stokes parameters are both necessary and sufficient to link on-orbit observations to an SI traceable standard

rE E E r

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

, , ,0 ,0 ,90 ,0I I I

Wavelength

Plane of Polarization

Retardation

,0 ,0 ,90 ,0

,45 ,0 ,135 ,0

,45 , 2 ,135 , 2

Q I I

U I I

V I I

Stokes Parameters Define the Degree of Polarizationand 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

1/ 22 2 2Q U V I

Q I

0Q U V

The CLARREO Design Objectivesin Shortwave Region

Calibration against SI traceable standards on-orbit

Identification of source of reflected solar irradiance

Intercalibration of other SW instruments on-orbit

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

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

End

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?

• 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?

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?

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?

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?

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

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




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Surface Air Temperature

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)

p pp

pdppn

22

)(1)(ln

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.

dSn

U

s

e

s

e

nUpU

S

iksiks

41

)(

GPS Radio Occultation (3)

• Refractivity

• “Dry” pressure

• Geopotential height

2w1-231-6 )hPaK10363()hPaK6.77(10)1(

T

p

T

pnN

)(

0

1-4 )K7521()()mhPa10402.4()(hp

h

d T

dpqhpdhNhp

0msl2222 /)

2

1()

2

1)(( grrh ss

r

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.?

Documents

Science Questions: Climate Benchmarking and On- Orbit SI Traceability CLARREO WORKSHOP Tuesday 21 October 2008 Jim Anderson, John Dykema, Stephen Leroy,