sorce science mtg. dec. 2003 r c willson - columbia university1 acrim instrument team roger s....

SORCE Science Mtg. Dec. 2003

R C Willson - Columbia University 1

ACRIM INSTRUMENT TEAM

Roger S. Helizon, Jet Propulsion LaboratoryInstrument Scientist/Project Mgr.

roger@simdac.jpl.nasa.gov

ACRIM Composite Total Solar Irradiance Time Series

ACRIM SCIENCE TEAM

Dr. Richard C. Willson, Columbia UniversityPrincipal Investigator

acrim@acrim.com

Dr. Alex Mordvinov, Head –Solar Activity LaboratoryInstitute Of Solar Terrestrial Physics, Irkutsk, Russia

Co-Investigator

Dr. James Hansen, Director – NASA/GISSCo-Investigator

Dr. Hugh S. Hudson – University of CA at BerkeleyCo-Investigator

SORCE Science Mtg. Dec. 2003

R C Willson - Columbia University 2

The Total Solar Irradiance Observational Database

• Continuous monitoring since 1978 by redundant, overlapping, satellite experiments

• Overlapping comparisons provide contiguous results at mutual precision levels

• Absolute uncertainty varies by experiment but is not demonstrably less than 0.1 % (SI)

• Traceability varies between experiments: ≥ 50 ppm/decade

• Scale differences of ± 0.4 % likely due to systematic errors in sensor metrology

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0.4 %

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ACRIM ‘gap’

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ACRIM Composite TSI Approach

• Uses

Original published results from TSI experiments

Overlapping comparisons to relate experiments at mutual precision level

Comparisons of ACRIM with Nimbus7/ERB to bridge the ACRIM ‘gap’

• Reconciles Composite time series to ACRIM3 ‘native scale’

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Comparison of ACRIM and PMOD Composite TSI

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Composite TSI Measurements and Models

• ACRIM Composite TSI

Uses original published results from TSI experiments

Uses Nimbus7/ERB ACRIM ‘gap’ ratio to link ACRIM1 and ACRIM2

• PMOD Composite TSI

Modifies published results from TSI experiments

Uses ERBS ACRIM ‘gap’ ratio to link ACRIM1 and ACRIM2

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The ACRIM - PMOD Composite Trend Difference

is an artifact of using the Nimbus7/ERB or ERBS ACRIM ‘gap’ ratios

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Comparison of Nimbus7/ERB and ERBS results (Simultaneous Daily Means)

ACRIM GAP

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Comparison of Overlapping Observationsduring ACRIM1, ACRIM ‘gap’ and ACRIM2 Periods

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Composite TSI Summary and Conclusions

• ERBS degradation during ACRIM ‘gap’ equals the ACRIM - PMOD trend difference

• PMOD adjustment of Nimbus7/ERB results during ACRIM ‘gap’ equals the ACRIM - PMOD trend difference

• The absence of a minimum-to-minimum trend in composite models using ERBS results to bridge the ACRIM ‘gap’ is an artifact of ERBS degradation

• Composite TSI time series using best extant data exhibit a minimum-to-minimum trend of + 0.04 %/decade during solar cycles 21 - 23