The Sun, Climate, and the Total and Spectral
Solar Irradiance Sensor
P. Pilewskie
Laboratory for Atmospheric and Space Physics (LASP)
University of Colorado, Boulder Colorado
peter.pilewskie@lasp.colorado.edu
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The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Sun-Climate Questions
• What is the solar forcing at decadal and longer time scales?
– Solar Irradiance Climate Data Record (CDR): time series of
measurements of sufficient length, consistency, and continuity to
determine climate variability and change.
• How does the climate system respond?
– What are the mechanisms of climate response? Requires
measurement of wavelength-dependent irradiance variability.
– Can a solar climate signal be attributed to unique mechanisms?
– Is the climate more sensitive to solar forcing than to other forcings, for
example, greenhouse gas forcing?
Attribution
• How much of the 20th-century warming trend was due to
anthropogenic forcing?
– Requires rigorous probabilistic analysis.
• What are the expected climate changes for the 21st century?
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The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Where Does the Atmosphere Get Its Energy?
Heat Flux*
2
Heat Source
Solar Irradiance
Heat Flux from Earth's Interior
Radioactive Decay
Geothermal
Infrared Radiation from the Full Moon
Sun's Radiation Reflected from Moon
Energy Generated by Solar Tidal Forces in the Atmosphere
Combustion of Coal, Oil, and Gas in US (1965)
Cycle
Variability
alone, ~ 0.1% of
EnergySolar
Dissipated
in Lightning
Discharges
Dissipation
Magnetic
Stormlargest
Energy energy source
thanof the
second
Radiation from Bright Aurora
Energy of Cosmic Radiation
Dissipation of Mechanical Energy of Micrometeorites
Total Radiation from Stars
Energy Generated by Lunar Tidal Forces in the Atmosphere
Radiation from Zodiacal Light
Total of All Non-Solar Energy Sources
* global average
TSI,
Physical Climatology, W.D. Sellers, Univ. of Chicago Press, 1965
Table 2 on p. 12 is from unpublished notes from
H.H. Lettau, Dept. of Meteorology, Univ. of Wisconsin.
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[W/m ]
340.20
0.0612
0.0480
0.0132
0.0102
0.0034
0.0034
0.0024
is0.0002
~ 10X
6.8E-05
4.8E-05
3.1E-05
2.0E-05
1.4E-05
1.0E-05
3.4E-06
0.0810
Relative Input
1.000
1.8E-04
1.4E-04
3.9E-05
3.0E-05
1.0E-05
1.0E-05
7.0E-06
larger
6.0E-07
2.0E-07
1.4E-07
9.0E-08
6.0E-08
4.0E-08
3.0E-08
1.0E-08
2.4E-04
T ≈ 30 K without Sun
The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Solar forcing critical to obtain agreement with temperature record
Global Surface Temperature
Surface Temperature Anomaly (K)
Anthropogenic Forcing
Natural & Anthropogenic Forcing
Model: ENSO+VOL, r=0.49
ENSO
VOLCANIC AEROSOLS
Residual Temperature Anomaly (K)
Global Surface Temperature Residuals
Model: SUN+ANTH, r=0.70
ANTHROPGENIC GASES
SUN
Amman, 2003
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The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
Lean, 2005
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Solar forcing is seen in both global and regional changes
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GISS General Circulation Middle Atmosphere
The Sun, Climate, and the Total and Spectral Solar
Irradiance
Sensor
Model:
Rind
et al., JGR, 2007
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TSI Record
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The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Fourth Assessment Report of the IPCC, 2007
There is uncertainty in solar
forcing since the start of the
industrial era but climate
response is even more uncertain:
−1
 ∂Fnet N ∂Fnet ∂Q i 
 ∆Fnet
∆Ts = 
−∑
∂
∂
∂
T
Q
T
i =1
i
s 
 s
SORCE 2010 Science Meeting
The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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2009
circa 1997
Global Energy Budget
340
340.2 W m-2
Kiehl and Trenberth, 1997
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Trenberth, K.E., et al., Bull Amer. Meteor. Soc., 2009
The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Now if only the models would all use the same Sun …
Raschke et. al, GRL, 32, 2005
AMIP-2: Atmospheric Model Intercomparison Project)
Offset (global average) among TSI
measurements
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A Contrast in Spectral Variability
Brightening with
decreasing solar
activity
Dimming with
decreasing solar
activity
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Spectral Heating Rate Differences:
Integrated
Sunspot Case (2005/04/30)
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Spectral Heating Rate Differences:
Integrated
Facula/Plage (2005/08/29)
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TSIS: The Total and Spectral Solar Irradiance Sensor
TIM
Total Irradiance
Monitor (TIM)
Spectral Irradiance
Monitor (SIM)
200 – 2400 nm
96% of TSI
SIM
Thermal Pointing Platform (TPS)
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History of TSIS
• TSIS selected in 1998 for the National Polar-orbiting
Operational Environmental Satellite System (NPOESS).
• TSIS was de-manifested along with other climate
sensors in 2006 following the Nunn-McCurdy Program
Review.
• Re-manifested in 2008 to fly on NPOESS C1
– High priority given in the Earth Science Decadal Survey
– 2007 NRC Workshop: Options to Ensure the Climate Record
Workshop
• February, 2010: New restructuring NPOESS, creation of
Joint Polar Satellite System (JPSS)
– TSIS awaiting manifestation.
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TSIS TIM Goals
• Goals unchanged from Glory TIM
– Performance
• Accuracy
• Stability
• Noise
0.01% (1 σ)
0.001%/yr (1 σ)
0.001% (1 σ)
– Measure TSI for >5 yrs
– Report four 6-hourly and one daily average TSI measurement
per day (Level 3 data products)
Key Technologies
NiP black cones
In-phase analysis of ESRs at shutter frequency
Precision aperture at front of instrument
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TSIS SIM Goals
• The TSIS SIM:
– Performance
•
•
•
•
Spectral Range
Accuracy
Stability
Signal-to-Noise
SIM SSI
200-2400 nm
0.2% (1 σ)
0.01%/yr (1 σ)
1000 @ 300 nm
20000 @ 800 nm
– Measure SSI for >5 yrs
– Report two SSI measurements per day
Key Technologies
3 Miniature ESRs with Féry prisms
Prism rotation angle (wavelength) measured in
focal plane.
Redundant SIM channels to track degradation.
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TSIS SIM derives heritage from SORCE SIM
SORCE SIM designed for long-term spectral irradiance
measurements
SORCE SIM
• SORCE SIM very reliable instrument - no instrument anomalies in
6+ years of continuous operation
• TSIS Operation and analysis software reused from SORCE with
minor changes
Incorporate lessons learned from SORCE SIM (and other LASP
programs) into TSIS SIM to meet CDR-level requirements:
Addition of 3rd SIM channel to reduce degradation uncertainties.
Reduce uncertainties in prism degradation correction to meet long- term
stability requirement.
• Ultra-clean optical environment to mitigate contamination
Improve noise characteristics of ESR and photodiode detectors to meet
measurement precision requirement.
• Improved ESR thermal design
• Larger dynamic range A/D plus signal integration
TSIS SIM
Improve absolute accuracy pre-launch calibration.
• NIST SI-traceable Unit and Instrument level pre-launch spectral calibration
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Calibration and Verification
• Both TIM and SIM trace their calibrations to the
standard Watt.
• All elements of TIM and SIM instrument equations are
calibrated at either the component or instrument level.
• End-to-end verification of TIM via the TSI Radiation
Facility (TRF)
• End-to-end verification of the SIM instrument with NIST
Spectral Irradiance and Radiance Responsivity
Calibrations using Uniform Sources (SIRCUS) and a new
LASP SSI Radiation Facility.
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TIM Uncertainty Budget
Correction
Origin
Value [PPM]
Distance to Sun, Earth & S/C
Analysis
33,537
0.1
Doppler Velocity
Analysis
57
0.7
Shutter Waveform
Component
100
1.0
Aperture
Component
1,000,000
28
Component
452
46
Cone Reflectance
Component
182
35
Non-Equivalence, ZH/ZR-1
Instrument
782
43
Servo Gain
Instrument
2,115
0.0
Standard Volt +DAC
Component
1,000,000
15
Component
800
3
Standard Ohm + Leads
Component
1,000,000
25
Dark Signal
Instrument
1,645
14
Pointing
Analysis
100
10
Measurement Repeatability (Noise)
Instrument
-
4
Uncertainty due to Sampling
Analysis
-
12
Diffraction
Pulse Width Linearity
Total RSS
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1σ [PPM]
85.5
The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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SIM Uncertainty Budget
Correction
Origin
Value [PPM]
1σ [PPM]
Distance to Sun, Earth & S/C
Analysis
33,537
0.1
Doppler Velocity
Analysis
43
1
Pointing
Analysis
0
100
Shutter Waveform
Component
100
1
Slit Area
Component
1,000,000
360
Component
3,000-22,000
500
Prism Transmittance
Component
230,000-450,000
1,000
ESR Efficiency
Component
1,000,000
1,000
Standard Volt + DAC
Component
1,000,000
50
Component
0
50
Standard Ohm + Leads
Component
1,000,000
50
Instrument Function Area
Instrument
1,000,000
1,000
Wavelength (∆λ/λ = 150 ppm)
Instrument
1,000,000
750
Non-Equivalence, ZH/ZR-1
Instrument
2,000
100
Servo Gain
Instrument
2,000
100
Dark Signal
Instrument
0
100
Noise
Instrument
-
100
Diffraction
Pulse Width Linearity
Total
RSS
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2000
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Current TSIS Plan for Continuous TSI Record
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TSI and SSI Continuity
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Possible TSI and SSI Continuity
DoD option to
move to am
orbit
Solar
Observation
Orbit
Glory TIM
Glory scheduled
for Nov. 2010 launch
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TSIS C1-replacement
JPSS – Solar 1
JPSS – Solar 2
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Summary: TSI
• JPSS TIM, like Glory Tim, will have unprecedented levels
of accuracy and stability.
• It is critical to have overlap between sensors.
– With overlap, the estimate of secular trends in TSI is very
difficult; without overlap, nearly impossible.
– NASA SORCE mission (launched in 2003) is a five-year mission,
extended to 2012.
– NASA Glory mission (launch in 2010) is planned for three years
(2013), although TIM is designed for five years (2015).
• First flight of TSIS yet to be determined. Delays beyond
2013-14 increase the probability of a gap in the TSI
record.
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The Sun, Climate, and the Total and Spectral Solar Irradiance Sensor
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Summary: SSI
• JPSS SIM incorporates changes from SORCE SIM to
improve accuracy and stability.
• Only a 6 year history of continuous SSI
– Commenced with SORCE SIM
– Slightly more than one-half of a single solar cycle observed.
– Before SORCE, comparisons made between individual
reference spectra, not time series
• There is no SIM on NASA Glory; SSI gap is likely.
– SOLAR SOLSPEC may help fill.
• Any delays in the flight of TSIS will add to the expected
gap in the spectral irradiance record.
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