Rotational variations in space-based TSI observations
Abstract
The Solar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor (TIM) is providing TSI data starting from 2003 to the present with the stability of less than 200 ppm of degradation. Furthermore, the recent collaborations among space-based total solar irradiance (TSI) observations has been successful and resolved the issue of the large difference in TSI in favor of SORCE TIM. While expecting less active solar maximum in solar cycle (SC) 24 than the past three solar cycles, the TSI observations of the present and the upcoming few more years will provide a natural experiment to study how the Sun varies during the less active solar cycle. Applying Ensemble Empirical Mode Decomposition (EEMD) method to daily TSI time series, we analyze the short-term variability of TSI associated with solar rotation from SORCE TIM and compare it with those from ACRIM3 (Active Cavity Radiometer Irradiance Monitor3, and VIRGO (Variability of Solar Irradiance and Gravity Oscillations). We determine the amplitude of the 27 and 13.5 days variations of TSI, during the declining phase, prolonged solar minimum of SC 23, and the rising phase of SC 24, by separating different modes of variability from three independent TSI observations. Comparisons of rotational variations of the TSI among SORCE TIM, ACRIM3, and VIRGO show good agreement in amplitude and phase during the declining phase between 2004 and 2007 and poor agreement in minimum phase after this period. There exist rotational variances during the prolonged minimum, even though their amplitudes are more than five times smaller than those in the declining phase. Absolute calibration offsets among measurements make it possible to construct a single composite TSI record, but the statistical analysis provides how much solar irradiance varies in different time scales. The amplitude and phase of TSI variability on different time scales and their statistical significance are presented, as needed in climate research.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGC51C0978L
- Keywords:
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- 7538 SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY Solar irradiance