HR: 09:00h
AN: U41B-05    [Abstracts]
TI: Detection of a secular trend in Total Solar Irradiance of + 0.04 % per decade during solar cycles 21 - 23
AU: * Willson, R C
EM: rwillson@acrim.com
AF: Columbia University, 12 Bahama Bend, Coronado, CA 92118 United States
AB: A `piecewise' continuous record of total solar irradiance (TSI) has been made by satellite experiments since November 1978. Assembling a contiguous record from this set of observations is a challenging task due to variations in quality of the different data sets, the limitation that a subtle secular trend might be masked by uncertainties in accuracy, precision and traceability and the necessity of relating the ACRIM1 and ACRIM2 results across a two year gap. The ACRIM approach to constructing a composite TSI record retains maximum precision and traceability by using results published by the science teams of the various experiments without alteration and the Nimbus7/ERB comparisons to link ACRIM1 and ACRIM2. The resulting ACRIM composite TSI demonstrates an upward trend of 0.04 (+/- 0.01) % per decade between activity minima during solar cycles 21-23. [Willson & Mordvinov] Another TSI composite, the `PMOD' [Frohlich & Lean], uses the same set of TSI data in a different approach and does not find a significant trend between minima. The PMOD composite uses TSI proxy models to justify modifying published results and relates ACRIM1&2 results using the overlapping data of the ERBS/ERBE experiment. The absence of a trend in the PMOD composite can be shown to be an artifact of uncorrected ERBS/ERBE degradation during the ACRIM gap. It will be further shown that chromospheric TSI regression (proxy) models are not competitive in accuracy, precision or traceability with satellite TSI observations and their use is therefore counter-indicated in construction of TSI composites. [Willson, R.C., A. V. Mordvinov, JGRL 30, pp. 1199-1202, 2003, Frohlich C., J. Lean, JGRL 25, pp. 4377-4380, 1998]
UR: http://acrim.com
DE: 7538 Solar irradiance
DE: 3359 Radiative processes
DE: 1600 GLOBAL CHANGE (New category)
DE: 1650 Solar variability
SC: Union [U]
MN: 2004 AGU Fall Meeting