sorce science mtg. dec. 2003 r c willson - columbia university1 acrim instrument team roger s....
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SORCE Science Mtg. Dec. 2003
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ACRIM INSTRUMENT TEAM
Roger S. Helizon, Jet Propulsion LaboratoryInstrument Scientist/Project Mgr.
ACRIM Composite Total Solar Irradiance Time Series
ACRIM SCIENCE TEAM
Dr. Richard C. Willson, Columbia UniversityPrincipal Investigator
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
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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