Total Solar Irradiance (TSI)

Daily mean data adjusted to 1 A.U. and corrected for sensor degradation

Table Of Contents:

1.) Composite Total Solar Irradiance database 1978-present, compiled by C. Frohlich and J. Lean

2.) ACRIM Composite TSI Time Series 1978-present, compiled by R. Willson

3.) SORCE (Solar Radiation and Climate Experiment) 2003-present, compiled by G. Rottman


4.) Total Solar Irradiance (TSI) data from individual satellites: ERBS (Oct 1984-Aug 2003), NIMBUS (Nov 16, 1978-Dec 13, 1993), NOAA9 (Jan 23, 1985-Dec 20, 1989), NOAA10 (Oct 22, 1986-Apr 1, 1987), SMM Feb 16, 1980-June 1, 1989), SOHO VIRGO (Jan 18, 1996-Nov 13, 1999) and UARS (Oct 4, 1991-Dec 31, 1997)


5.) Older, archival databases:

5a.) Dr. John Arvesen's Solar Spectral Irradiance data at the top of the atmosphere in the 300-2500 nm wavelength range (UV to visible), from NASA research aircraft -- 11 flights

5b.) Charles Greeley Abbot solar constant database -- Note: 2 years of scientific investigation are needed to bring this database into a scientifically useable research database

Total Solar Irradiance (All ftp)

Total Solar Irradiance Measurements

The "solar constant" is, in fact, not constant. Recent satellite observations have found that the Total Solar Irradiance (TSI), the amount of solar radiation received at the top of the Earth's atmosphere, does vary -- see the graph for the results from six satellites. "The variations on solar rotational and active region time scales are clearly seen. The large, short-term decreases are caused by the TSI blocking effect of sunspots in magnetically active regions as they rotate through our view from Earth. The peaks of TSI preceding and following these sunpot "dips" are caused by the faculae of solar active regions whose larger areal extent causes them to be seen first as the region rotates onto our side of the sun and last as they rotate over the opposite solar limb." [Excerpted from the UARS descriptive text] The TSI provides the energy that determines the Earth's climate.

• Radiometrically the composite is based on the ACRIM-I and II records; before the start of the ACRIM-I measurements in 1980, during the spin mode of SMM, and during the gap between ACRIM-I and II, corrected data are inserted by shifting the level to fit the corresponding ACRIM data over an overlapping period of 250 days on each side of the ACRIM sets. In early 1996 the VIRGO data take over, again shifted to agree with ACRIM-II. Finally the composite record is adjusted via ACRIM-II to SARR (Space Absolute Radiometer Reference) which was introduced by Commelynck et al. (1995) and allows the comparison of different space experiments. The data from ERBE and ACRIM-III, as well as an empirical model, are used for comparisons and for internal consistency checks. For more information, please visit the web site of the World Radiation Center.
  • TSI Composite Database plot
  • TSI Composite Data 1978-present daily data (ASCII)
  • TSI Composite Database plot of data 1978-1999.

• For up-to-date data, please visit the ACRIM home page. ACRIM3 (Active Cavity Radiometer Irradiance Monitor 3) monitors the total variability of solar irradiance with active cavity radiometer solar monitoring sensors. ACRIM 3 was successfully launched on board the NASA ACRIMSAT spacecraft on December 20, 1999.
  • The ACRIM composite time series is constructed from combinations of satellite TSI data sets. NNAA3 uses Nimbus7 ERB and ACRIM1,2 and 3 results (plot). NNAVA3 replaces the 1996-1998 ACRIM2 results with the two year VIRGO results (plot).

• SORCE (Solar Radiation and Climate Experiment) was launched on Jan 25, 2003, to provide precise measurements of solar radiation. It is operated by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado (CU) in Boulder, Colorado, USA. It continues the ERB measurements begun in 1979 and the ACRIM measurements.
• For data information, please visit the SORCE (Solar Radiation and Climate Ex Sciences (GES) Distributed Active Archive Center (DAAC) in Greenbelt, Maryland, USA. Please visit the NASA DAAC or the SORCE webpage to access these data.

• 4a. NASA Earth Radiation Budget Satellite (ERBS) satellite data October 1984-August 2003 descriptive text (WORD doc)
  • From 1984 to present, total solar irradiance (TSI) values were obtained from the solar monitor on the Earth Radiation Budget Satellite (ERBS) nonscanner instrument. The ERBS solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions. The ERBS satellite was placed into orbit on October 5, 1984, and the solar monitor is still operating properly, after almost 18 years. The measurement precision is about 0.01 percent, while the accuracy is 0.2 percent. At least once every 14 days, the Sun is observed by the monitor. The averaged irradiance values represent an almost instantaneous level, and not a daily average.
    • ERBS satellite bi-weekly database (txt)
• 4b. NASA NIMBUS satellite data November 16, 1978-December 13, 1993 data format (txt)
  • From 1978 to 1993, total solar irradiance (TSI) values were obtained from the solar monitor on the NASA NIMBUS nonscanner instrument. The NIMBUS solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions. The paper "The Nimbus-7 Solar Total Irradiance: A new Algorithm for its Deviation" by D.V. Hoyt, H.L. Kyle, J.R. Hickey, and R.H. Maschoff (JGR, vol 97, pp 51-63) describes the methodology used to reduce the data.
    • NIMBUS satellite bi-weekly database (txt) in x-y plottable format.
• 4c. NOAA 9 and 10 satellite data January 23, 1985-December 20, 1989 data format (txt)
  • From 1985 to 1989, total solar irradiance (TSI) values were obtained from the solar monitor on the NOAA9 and NOAA 10 nonscanner instruments. The NOAA solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
    • NOAA9 satellite database (txt) in x-y plottable format.
    • NOAA10 satellite bi-weekly database (txt) in x-y plottable format.
• 4d. NASA Solar Maximum Mission (SMM) satellite data February 16, 1980-June 1, 1989 data format (txt)
  • From 1980 to 1989, total solar irradiance (TSI) values were obtained from the solar monitor on the SMM nonscanner instruments. The SMM solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
    • SMM satellite daily database (txt) in x-y plottable format.
• 4e. SOHO VIRGO, v2 satellite data February 16, 1980-June 1, 1989 data format (txt)
  • From 1980 to 1989, total solar irradiance (TSI) values were obtained from the solar monitor on the SMM nonscanner instruments. The SMM solar monitor is an active cavity radiometer, similar in design to the Active Cavity Radiometer Irradiance Monitors (ACRIM) which have flown on the NASA Solar Maximum Mission (SMM), Upper Atmosphere Research Satellite (UARS), and Atmospheric Laboratory for Applications and Science (ATLAS) spacecraft missions.
    • SOHO VIRGO v2 satellite daily database (txt) in x-y plottable format.
    • SOHO VIRGO v2 satellite plot of daily database 1996-1999.
• 4f. NASA Upper Atmosphere Research Satellite (UARS) Active Cavity Radiometer Irradiance Monitor II Experiment (ACRIM II) TSI satellite data October 4, 1991-December 31, 1997 data format (txt)
  • The second Active Cavity Radiometer Irradiance Monitor experiment (ACRIM II) was launched in September 1991 as part of the science payload of the Upper Atmosphere Research Satellite (UARS). The variations on solar rotational and active region time scales are clearly seen. The large, short-term decreases are caused by the TSI blocking effect of sunspots in magnetically active regions as they rotate through our view from Earth. The peaks of TSI preceding and following these sunpot "dips" are caused by the faculae of solar active regions whose larger areal extent causes them to be seen first as the region rotates onto our side of the sun and last as they rotate over the opposite solar limb. The downward trend through the 1991-1997 period is similar in slope and amplitude to that observed by ACRIM I during the decling phase of solar cycle 21. From the peak of solar cycle 21 to its minimum the TSI decreased by about 0.08 percent. It appears likely from the ACRIM II results thus far that the cycle 22-23 minimum in TSI will occur during 1997, near the average solar cycle period of about 11 years after the cycle 21-22 minimum, and with a similar decrease relative to the maximum of cycle 22 in the 1990-1991 period.
    • NASA UARS satellite daily database (txt) in x-y plottable format.

• 5a. Dr. John C. Arvesen's solar spectral irradiance at the top of the atmosphere -- UV to visible (200-2495 nm)
  • NASA research aircraft database (txt) including descriptive text
    • Results are presented of an experiment to determine extraterrestrial solar spectral irradiance at the Earth's mean solar distance within the 300-2500 nm wavelength region. Spectroradiometric measurements were performed during eleven research flights on board a NASA CV-990 aircraft at altitudes between 11.6 km and 12.5 km. Precision of the measurements was better than +/- 1 percent. Absolute accuracy of the resultant extraterrestrial solar spectral irradiance is about +/-3 percent over most of the measurement range. A listing of results is presented at intervals varying from 0.1 nm throughout most of the uv-visible Fraunhofer region to 5 nm in the continuum region of the infrared. Additionally, a listing of solar spectral irradiance, smoothed over the detailed Fraunhofer structure, is presented for engineering use.

• 5b. Charles Greeley Abbot solar constant database 1902-1954
  • Descriptive text and data format (text)
    • The Smithsonian Astrophysical Observatory (APO) gathered solar constant data during at least 49 years of solar monitoring. The solar constant is the total amount of energy received from the sun per unit time per unit area exposed normally to the Sun's rays at the average Sun-Earth distance and outside of the Earth's atmosphere. The purpose of this APO porject was to determine an accurate value for this energy flux and to determine whether or not the Sun's total energy output is indeed constant in time.
    • Notwithstanding all of the short comings and controversy inherent in the data, this program is the longest and most carefully conducted solar radiation program made in the 20th century.
    • Dr. Vernon Derr estimated a research effort of two qualified scientists studying the data for about two years would be needed to fully understand and correct the database. The 47 data files are available via the ftp site.

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