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Figure 1: SATIRE-S daily TSI values (grey) and 121-days running mean (horizontal line at 1360.75 W/m² to illustrate the change in solar minima).

Figure 2: NRLTSI2 daily values (grey) and 121-days running mean (horizontal line at 1360.45 W/m² to illustrate the stability of the solar minima). Only data onward of 1976 are shown.

Figure 3: Timeseries of SATIRE-S (red) and NRLTSI2 (black) TSI reconstruction models after 121-days running mean. The daily NRLTSI2 values are shown in grey. Horizontal line at 1360.75 W/m² illustrates the change in solar minima.

Figure 4: (rescaled) ERB timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 5: (rescaled) ACRIM1 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 6: ERBS timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 7: (rescaled) ACRIM2 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 8: (rescaled) DIARAD timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 9: PMO06 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

Figure 10: (rescaled) ACRIM3 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. Some outliers are in red.

Figure 11: (rescaled) TIM/SORCE timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

Figure 12: (rescaled) SOVA/Picard timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

Figure 13: (rescaled) PREMOS timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

Figure 14: (rescaled) TIM/TCTE timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

Figure 15: (rescaled) TIM/TSIS-1 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

Figure 16: Timeseries of individual TSI measurements after selection and harmonization. A 121-day running mean is used to remove the short-term solar noise. The 1361 W/m² horizontal line is shown to illustrate the stability between the solar minima.

Figure 17: Illustration of the gap filling process. The black curve is an original TSI record with many data gaps (in this example the TIM/TCTE in 2014). The green curve is the SATIRE-S model. The red curve shows how the gaps can be filled by mixing the incomplete record with the (complete) SATIRE-S record.

Figure 18: C3S composite daily TSI values (grey) and 121-day running mean (red). The NRLTSI2 model, with an offset of 0.31 W/m² to match the curves, is shown in black.

General definitions

Term

Definition

Earth Radiation Budget (ERB)

The difference between the incoming radiant energy to the Earth (directly dependent on the TSI) and the outgoing radiant energy due to reflection and thermal emission.

Electrical substitution cavity radiometer

Radiant energy measurement principle in which the radiant energy absorbed in a cavity is equilibrated with electrical power dissipated in a second non-illuminated equivalent cavity.

Magnetogram

Image of the Sun showing the strength and the polarity of its magnetic fields. The image is taken by an instrument called magnetograph.

Scattering and diffraction

Change of light direction due to interaction with matter. The diffraction is a spreading of light without changing in the average direction, while scattering is the deflection of the light with a clear change of direction.

Astronomical Unit (A.U.)

Unit of length equal to the mean distance between the center of the Earth and the center of the Sun.

Irradiance

Flux of radiant energy per unit area. The irradiance is usually expressed in W/m² unit.

Solar cycles

The solar cycles are nearly periodic 11-year changes in the Sun's activity.

Solar minima, quiet Sun

The 11-year solar cycle is characterized by periods of least solar activity called solar minima or quiet Sun. During these periods the average TSI is also minimum.

Bright facula

A solar facula is a bright spot in the photosphere. This part of the Sun disk has higher TSI than its surrounding area.

Dark sunspot
Umbra
Penumbra
Network

Opposite to a facula, a sunspot is a part of the Sun disk that appears darker, i.e. with a lower TSI, than its surrounding area. The sunspots can be decomposed in two main regions: the central umbra (with the lowest TSI) and the surrounding penumbra (with higher TSI than in the central umbra). The sunspots are often organized in network.

Bias

bias-corrected Root Mean Squared Difference

The bias (b) is the average value of the difference of the data (x_i ) with respect to a reference dataset (r_i ), where N is the number of data points:

Mathdisplay
b=\frac{1}{2}\sum_{i=1}^{N}(x_i-r_i)

The bias-corrected Root Mean Squared Difference (bcRMSD) is the square root of the average of the square of the differences with respect to the reference dataset, once the bias (b) has been removed from the data points (x_i ) (therefore the term "bias corrected"):

Mathdisplay
bcRMSD=\sqrt{\frac{1}{N}\sum_{i=1}^{N}(x_i-b-r_i)^2)}

Climate Data Store (CDS)

The front-end and delivery mechanism for data made available through C3S.

Climate Data Record (CDR)

Sufficiently long, accurate and stable time series of a climate variable to be useful to address climate variability and change.

Interim Climate Data Record (ICDR)

An interim CDR is an extension of a CDR that meets some timeliness requirements needed in some applications, e.g. for use in the "State of the Climate" reports. These preliminary data might not be fully validated and may need to be reprocessed before inclusion in the finale CDR.

Scope of the document

This document is the Algorithm Theoretical Basis Document (ATBD) for the generation of the version 3 of the Climate Data record (CDR) and Interim Climate Data Record (ICDR) v3.1 of daily Total Solar Irradiance (TSI) for the Copernicus Climate Change Service (C3S).

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Relative variations of the TSI in phase with the 11-year solar cycle of the order of 1 W/m² are now well established, as summarized by Dewitte & Nevens (2016) [D1] and Dewitte & Clerbaux (2017) [D2]. Apart from these true TSI variations, differences in the absolute level well above 1 W/m² are observed between the different instruments indicating limitations of the absolute accuracy. For this reason, multiplicative correction factors are determined to scale all the timeseries to a same radiometric level. These factors are determined by optimizing the consistency over the overlap periods that exist between the different instruments. Still, a reference level must be defined and this is done in this work in such a way that the average of the correction factors for the 5 most accurately calibrated instruments is set to 1.0. These 5 instruments are: Physikalisches und Meteorologisches Observatorium 06 (PMO06), Precision Monitor Sensor (PREMOS), and the TIM instruments on the Solar Radiation and Climate Experiment (TIM/SORCE), on the Total solar irradiance Calibration Transfer Experiment (TIM/TCTE), and on the International Space Station (TIM/TSIS1).

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Table 1: Total Solar Irradiance space instruments (acronyms definitions in footnote). The instruments used in the C3S v3.0 and v3.1 daily TSI composite are highlighted in bold.

Instrument¹	Platform(s)	Used	Operation period(s)	References
TCFM	Mariner-6 & 7	No	1969	Plamondon (1969)
ERB	Nimbus 6	No	1975	Hickey et al (1976)
ERB	Nimbus 7	Yes	1978 - 1993	Hickey et al (1980)
ACRIM 1	SMM	Yes	1980-1989	Willson et al. (1980)
Solcon 1	Spacelab 1	No	1983	Crommelynck et al (1987)
ERBE	ERBS	Yes	1984-2003	ERBE (1986)
ERBE	NOAA-9	Yes	1985-1989	ERBE (1986)
ACRIM 2	UARS	Yes	1991-2001	Willson (1994)
Solcon 2	Atlas 1	No	1992	Crommelynck et al (1994)
Sova 1	Eureca	No	1992-1993
Sova 2	Eureca	No	1992-1993	Romero et al. (1994)
ISP-2	Meteor-3 No 7	No	1994	Sklyarov et al. (1996)
DIARAD/VIRGO	SOHO	Yes	1996-present	Dewitte et al. (2004)
PMO06V-A/VIRGO	SOHO	Yes	1996-present	Froehlich et al. (1997)
ACRIM 3	ACRIMSAT	Yes	2000-2014	Willson et al. (2003)
TIM	SORCE	Yes	2003-2020	Kopp et al. (2005)
DIARAD/SOVIM	ISS	No	2008	Mekaoui et al. (2010)
SIM	FY 3A	No	2008-2015	Fang et al. (2014)
SOVA	Picard	Yes	2010-2014	Dewitte et al. (2013a)
PREMOS	Picard	Yes	2010-2014	Schmutz et al. (2012)
SIM	FY 3B	No	2011-present	Fang et al. (2014)
TIM	TCTE	Yes	2013-2019	Kopp et al. (2016)
SIM	FY 3C	No	2013-present	Wang et al. (2017)
TIM	TSIS-1	Yes	2018- present	Kopp, G. (2020),
CLARA	NorSat	No	2018- present	Walter et al. (2017)
DARA	PROBA-3	No	To be launched

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1 TCFM: Temperature Control Flux Monitor; ERB: Earth Radiation Budget; ACRIM: Active Cavity Radiometer Irradiance Monitor; SMM: Solar Maximum Mission; SOLCON: Solar Constant; ERBE: Earth Radiation Budget Experiment; ERBS: Earth Radiation Budget Satellite; NOAA: National Oceanic and Atmospheric Administration; UARS: Upper Atmosphere Research Satellite; ATLAS: Atmospheric Laboratory for Applications and Science; SOVA: Solar Variability; EURECA: European Retrievable Carrier; ISP: Solar Constant Gauge; DIARAD: Differential Absolute Radiometer; VIRGO: Variability of Irradiance and Gravity Oscillations; SOHO: Solar and Heliospheric Observatory; PMO: Physikalisches und Meteorologisches Observatorium; TIM: Total Irradiance Monitoring; SORCE: Solar Radiation and Climate Experiment; SOVIM: Solar Variability Irradiance Monitor; SIM: Solar Irradiance Monitor; FY: Feng Yung; PREMOS: Precision Monitor Sensor; TCTE: Total Solar Irradiance Calibration Transfer Experiment.

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2. Input and auxiliary data

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• The NRLTSI2 record is explicitly not used when constructing the C3S v3.0 and v3.1 daily TSI composites, so it can be used as independent source for the validation (see methodology and results in PQAD [D3] and PQAR [D5] documents).

2.1.1 SATIRE-S

The SATIRE-S (Spectral And Total Irradiance Reconstructions, Yeo et al, 2014a and 2014b) is a reconstruction of the TSI over the 1974-present-day period using full-disc magnetograms and continuum images of the Sun. It uses the data from the National Solar Observatory Photospheric magnetogram (NSO KP) (1974-1999), SOHO/ Michelson Doppler Imager (MDI) (1999-2009) and Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) (since 2010). These observations allow for the estimation of the fractional coverage of: quiet Sun, sunspot umbrae, sunspot penumbrae, faculae and network. A regression between these indices and the TSI is then derived and used in the reconstruction. The SATIRE-S data starts on 23rd August 1974 and provides data until 8th July 2023 (at time of writing). New data are regularly added to the timeseries.

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SATIRE-S

Full name: Spectral And Total Irradiance Reconstructions

Organization: Max-Planck-Institut für Sonnensystemforschung (MPI for Solar System Research)

Period covered

C3S period selected

C3S adjustment factor

23.08.1974 – 08.07.2023

01.01.1979 – 06.11.1980

Set to 1.00015

Data availability

C3S Data availability (filled)

C3S estimated noise level

100%

100% (100%)

Set to 0.5 W/m²

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Figure 1: SATIRE-S daily TSI values (grey) and 121-days running mean (horizontal line at 1360.75 W/m² to illustrate the change in solar minima).

DATA SOURCE: http://www2.mps.mpg.de/projects/sun-climate/data_body.html

References: Yeo et al. (2014a), Yeo et al. (2014b).

Notes:

The model shows marked differences in solar minima levels
The quality of the reconstruction is better when SDO/HMI is used, i.e. from 30.04.2010 onward (S. Dewitte, pers. comm.)

2.1.2 NRLTSI2

NRLTSI2 is the version 2 of the Naval Research Laboratory’s (NRL) solar variability models for Total Solar Irradiance (TSI). This CDR was created at the Space Science Division of the Naval Research Laboratory (NRL) in collaboration with the Laboratory for Atmospheric and Space Physics (LASP) of the University of Colorado. The NRLTSI2 CDR is published as part of the NOAA CDR Program and is documented by Coddington et al. (2015, 2016). In this model, the daily TSI is estimated from the observation of the bright faculae and the dark sunspots on the solar disk. A linear regression between these proxies of solar activity and the TIM/SORCE TSI was established and used in the reconstruction. The model assumes a quiet Sun TSI of 1360.45 W/m² (Kopp and Lean, 2011) as estimated from the TIM/SORCE measurement at solar minimum. The reconstruction starts on 1st January 1882 and provides data until 31st December 2022 (at time of writing). New data are regularly added to the timeseries, on a quarterly basis.

NRLTSI2

Full name: Naval Research Laboratory Total Solar Irradiance version 2

Organization: U.S. Naval Research Laboratory

Period covered

C3S period selected

C3S adjustment factor

01.01.1882 – 31.12.2022

Not used in the composite

(not applicable)

Data availability

C3S Data availability (filled)

C3S estimated noise level

100%

100% (100%)

(not applicable)

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Figure 2: NRLTSI2 daily values (grey) and 121-days running mean (horizontal line at 1360.45 W/m² to illustrate the stability of the solar minima). Only data onward of 1976 are shown.

DATA SOURCE:

References: Coddington et al. (2015), Coddington et al. (2016).

Notes:

The record is regularly updated with new data.
The last year data are preliminary (ICDR concept) and later incorporated in the final CDR.

2.1.3 SATIRE-S / NRLTSI2 intercomparison

Figure 3 shows the SATIRE-S and NRLTSI2 timeseries over the 1975 – 2022 time period. The 2 models show very close agreement over solar cycle 23 (1996 – 2008) but otherwise exhibit significant differences, especially in the level of the solar minima in 1986, 1996 and 2019.

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Note about the graphs in Figure 4 to Figure 15 : the graphs show the timeseries of the satellite record (in green the daily and orange the 121-days running mean) after rescaling to the C3S record (in black). The NRLTSI2 data is also shown (in brown) after a rescaling on the same overlap period. The parts of the satellite record which are discarded in the C3S composite are in red (daily) and blue (121-days running mean).

2.2.1 ERB on NIMBUS7

ERB on Nimbus 7

Full name: Earth Radiation Budget on NIMBUS7

Organization: NASA / NOAA

Period covered

C3S period selected

C3S adjustment factor

16.11.1978 – 13/12/1993

01.01.1981 – 31.12.1989

0.992447

Data availability

Data availability (gap filled)

C3S estimated noise level

83.24%

89.45% (100% )

0.318 W/m²

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Figure 4: (rescaled) ERB timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE: https://opendap.larc.nasa.gov/opendap/NIMBUS-7/ERB_Ch10C_TSI_NAT/nimbus7_tsi_19781116_19931213

References: Hickey et al. (1980)

Notes:

The ERB / NIMBUS-7 instrument has no aging monitoring capability.
Data before 1981 and after 1990 have been discarded due to marked differences with the TSI models. The problem affecting ERB/Nimbus 7 data during the so-called "ACRIM gap" period (in between ACRIM1 and ACRIM2) has been reported by other teams e.g. Lee et al. (1995) and Chapman et al. (1996).
During the selected period, there are many (332) gaps of 1 day in the record (they are interpolated).
Outliers (Julian day): 2447881, 2445468, 2445492

2.2.2 ACRIM1 on SMM

ACRIM1 on SMM

Full name: Active Cavity Radiometry Irradiance Monitor on Solar Maximum Mission

Organization: NASA

Period covered

C3S period selected

C3S adjustment factor

16.02.1980 – 14.07.1989

07.11.1980 – 14.07.1989

0.995568

Data availability

Data availability (gap filled)

C3S estimated noise level

90.14 %

90.00% (97.96%)

0.270 W/m²

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Figure 5: (rescaled) ACRIM1 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE ² : http://acrim.com/RESULTS/data/acrim1/acrim1_hdr.rtf
(https://web.archive.org/web/20170209071650/http://acrim.com/RESULTS/data/acrim1/acrim1_hdr.rtf)

References : Willson et al. (1981)

Notes:

In general, the running mean shows a close agreement with the NRLTSI2 reconstruction, except over the very early period (1980).
The ACRIM1 instrument was launched on the SMM spacecraft in February 1980. From November 1980 to April 1984 the SMM attitude control was degraded, leading to the so-called "ACRIM1 spin period" (Willson, 1994).
In 1984, there are data gaps. These gaps are short enough to be interpolated before ingestion in the composite, except one gap of 63 consecutive days.
Outliers (Julian day) : 2444642, 2447772, 2444804, 2444856, 2444884, 2445473, 2445533, [2444589:2444598], 2447137, 2447138

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2 Information retrievable from the web.archive.org serves as an interim solution due to ongoing issues with the ACRIM server. Future document versions will include updated links when available.

2.2.3 ERBS

ERBS

Full name: Earth Radiation Budget Satellite solar monitor

Organization: NOAA

Period covered

C3S period selected

C3S adjustment factor

17.12.1984 – 23.04.2003

02.07.1987 - 06.02.2001

0.997149

Data availability

Data availability (gap filled)

C3S estimated noise level

98.46%

97.93% ( 100%)

0.270 W/m²

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Figure 6: ERBS timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE ³ : An application, such as FileZilla, WinSCP or Wget, might be needed to open FTP sites.: ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_IRRADIANCE/ERBS2003.TXT

References: ERBE (1986)

Notes:

As the ERBS sampling period is 14 days, and as the ERBS measurements are relatively noisy, the "denoised" ERBS version from Mekaoui and Dewitte (2008) is used.
In general, the running mean shows a close agreement with the NRLTSI2 reconstructions, except over the very early period (before 02.07.1987) which has been discarded from the composite. At end of mission, from 06.02.2001 onward, there is also an apparent difference with respect to the models and the data are discarded from this date onward.
Outliers: none

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3 An application, such as FileZilla, WinSCP or Wget, might be needed to open FTP sites.

2.2.4 ACRIM2

ACRIM2

Full name: Active Cavity Radiometry Irradiance Monitor on Upper Atmosphere Research Satellite

Organization: NASA

Period covered

C3S period selected

C3S adjustment factor

04.10.1991 – 05.05.2001

0.997821

Data availability

Data availability (gap filled)

C3S estimated noise level

93.35%

93.35% (100%)

0.215 W/m²

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Figure 7: (rescaled) ACRIM2 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE⁴ : http://acrim.com/RESULTS/data/acrim2/dayu2deg_ts_0110041651_hdr.txt
https://web.archive.org/web/20170209065021/http://acrim.com/RESULTS/data/acrim2/dayu2deg_ts_0110041651_hdr.txt

References: Willson (1994)

Notes:

Close agreement with NRLTSI2, except during the solar minimum on 1996, but in this case the agreement with SATIRE-S is correct.
Outliers (Julian day): 2451423, 2451539

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4 Information retrievable from the web.archive.org serves as an interim solution due to ongoing issues with the ACRIM server. Future document versions will include updated links when available.

2.2.5 DIARAD / VIRGO on SOHO

DIARAD / VIRGO on SOHO

Full name: Differential Absolute Radiometer on Variability of Irradiance and Gravity Oscillations

Organization: RMIB

Period covered

C3S period selected

C3S adjustment factor

18.01.1996 - present

01.01.1997 – present

0.996449

Data availability

Data availability (gap filled)

C3S estimated noise level

93.95%

93.78% (98.33%)

0.121 W/m²

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Figure 8: (rescaled) DIARAD timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE⁵ : http://remotesensing.oma.be/meteo/view/en/3385923-diarad.level2.web.html

References: Dewitte et al. (2004)

Notes:

In general, close agreement between DIARAD and the models except for the first months which have been discarded as in Dewitte and Nevens (2016) and in Froehlich (2003).
The aging monitoring cavity failed on 9 Oct 2017 and since then the aging is extrapolated. Although "at risk", the data is kept as it stays as long as it stays in agreement with NRLTSI2. This is justified by the few number of space instruments in the ICDR period (2021 onward).
Since 2010, there is an annual cycle apparent in the DIARAD/VIRGO record. This cycle has been corrected.
Two gaps are too long to be interpolated: one of 104 days (2008) and one of 53 days (2021).
Outliers (Julian day): 2452313, 2451093

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5 As of 28.11.2023, the provided link to the dataset is not functional. This is the only data source in place for this dataset. The data provider has been alerted to this issue, and efforts are underway to resolve it for future accesibility.

2.2.6 PMO06 on VIRGO

PMO06 on VIRGO

Full name: Physikalich Meteorologisches Observatorium version 06

Organization: Physikalich-Meteorologisches Observatorium Davos and World Radiation Center

Period covered

C3S period selected

C3S adjustment factor

21.02.1996 – 13.05.2022

01.01.1997 – 13.05.2022

1.000181

Data availability

Data availability (gap filled)

C3S estimated noise level

97.87%

97.83% (98.88%)

0.173 W/m²

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Figure 9: PMO06 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. The parts discarded are in red and blue.

DATA SOURCE⁶ : ftp://ftp.pmodwrc.ch/pub/data/irradiance/virgo/TSI/VIRGO_TSI_Daily_V8_20230728.zip

References: Froehlich et al. 1997

Notes:

As for DIARAD, close agreement with the models except for the first months (before 01.01.2017) which have been discarded. The early increase of the VIRGO radiometers is also discussed in Froehlich (2003).
However, there is a significant departure from the models during the recent solar minima of 2020. As for DIARAD, the PMO06 data is kept due to the few number of instruments in the ICDR period.
Outliers: none.

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6 An application, such as FileZilla, WinSCP or Wget, might be needed to open FTP sites.

2.2.7 ACRIM3

ACRIM3

Full name: Active Cavity Radiometry Irradiance Monitor on ACRIMSAT

Organization: NASA

Period covered

C3S period selected

C3S adjustment factor

05.04.2000-05.03.2013

1.000078

Data availability

Data availability (gap filled)

C3S estimated noise level

97.44%

97.44% (100%)

0.126 W/m²

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Figure 10: (rescaled) ACRIM3 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models. Some outliers are in red.

DATA SOURCE ⁷ : http://acrim.com/RESULTS/data/acrim3/daya2sddeg_ts4_Nov_2013_hdr.txt
(https://web.archive.org/web/20170209060758/http://acrim.com/RESULTS/data/acrim3/daya2sddeg_ts4_Nov_2013_hdr.txt)

References: Willson et al. (2003)

Notes:

In general, good agreement with the 2 models, except during the solar minimum of 2009 and also at end of mission in 2013.
A slow decrease of the TSI with respect to the 2 models is visible; this could indicate that aging is not fully corrected.
Outliers (Julian day): 2453165, 2454116, 2454117, 2454118, 2455212, 245513, 2455214, 2455213.

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7 Information retrievable from the web.archive.org serves as an interim solution due to ongoing issues with the ACRIM server. Future document versions will include updated links when available.

2.2.8 TIM on SORCE

TIM on SORCE

Full name: Total Irradiance Monitor (TIM) on SOlar Radiation and Climate Experiment (SORCE)

Organization: Laboratory for Atmospheric and Space Physics (LASP)

Period covered

C3S period selected

C3S adjustment factor

25.02.2003 – 25.02.2020

(All)

1.000256

Data availability

Data availability (gap filled)

C3S estimated noise level

94.72%

94.72% (96.62%)

0.089 W/m²

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Figure 11: (rescaled) TIM/SORCE timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

DATA SOURCE: http://lasp.colorado.edu/data/sorce/tsi_data/daily/sorce_tsi_L3_c24h_latest.txt

References : Kopp et al. (2005)

Notes:

With respect to SATIRE-S (black curve), there is an apparent increase of the TIM/SORCE TSI. For this reason, a correction was applied in the version 2 of the C3S CDR. However, this increase is not visible with respect to NRLTSI2 and therefore, no correction will be performed in version 3.
There are 2 long data gaps of 144 days and 66 days in 2013-2014. They are not interpolated using the model.
Outliers: none.

2.2.9 SOVA on Picard

SOVA on Picard

Full name: SOlar VAriability Experiment on Picard

Organization: RMIB

Period covered

C3S period selected

C3S adjustment factor

27.08.2010 – 03.11.2013

0.999345

Data availability

Data availability (gap filled)

C3S estimated noise level

80.43%

80.43% (100%)

0.145 W/m²

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Figure 12: (rescaled) SOVA/Picard timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

DATA SOURCE: http://idoc-picard.ias.u-psud.fr:8182/sitools/upload/sovap-data.dat

Reference : Dewitte et al. (2013a)

Notes:

The IDOC-PICARD website provide daily and hourly data. The daily data are less complete than the hourly, we have therefore reconstructed the daily from the hourly.
Outliers: none

2.2.10 PREMOS on Picard

PREMOS on Picard

Full name: Precision Monitor Sensor on Picard

Organization: Physikalich-Meteorologisches Observatorium Davos and World Radiation Center

Period covered

C3S period selected

C3S adjustment factor

27.07.2010 – 20.08.2013

1.000256

Data availability

Data availability (gap filled)

C3S estimated noise level

90.19%

90.19% ( 100%)

0.086 W/m²

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	figure13
	figure13

Image Modified

Figure 13: (rescaled) PREMOS timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

DATA SOURCE: (daily and hourly data, see note here after)
http://idoc-picard.ias.u-psud.fr:8182/sitools/upload/premos_daily_means_20130705.dat
http://idoc-picard.ias.u-psud.fr/sitools/upload/premos_hourly_means_20140429.dat

References : Schmutz et al. (2012)

Notes:

Short record but with excellent agreement with both the SATIRE-S and NRMTSI2 models.
The daily data is less complete than the hourly one. In the C3S composite we have recomputed the daily values from the hourly ones.
Outliers: none

2.2.11 TIM on TCTE

TIM on TCTE

Full name: Total Irradiance Monitoring on Total Solar Irradiance Calibration Transfer Experiment

Organization: Laboratory for Atmospheric and Space Physics (LASP)

Period covered

C3S period selected

C3S adjustment factor

16.12.2013 – 15.05.2019

0.999771

Data availability

Data availability (gap filled)

C3S estimated noise level

83.46%

83.46% (93.98%)

0.092 W/m²

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	figure14
	figure14

Image Modified

Figure 14: (rescaled) TIM/TCTE timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

DATA SOURCE: http://lasp.colorado.edu/data/sorce/tsi_data/daily/sorce_tsi_L3_c24h_latest.txt

References : Kopp et al. (2016), (TCTE 2014)

Notes and references:

Good agreement with the 2 models.
During 2014 there are frequent gaps of 6-days duration that have been interpolated.
End of 2018-early 2019 there is a 119 days long gap that is not interpolated.
After the gap, and until end of mission, the decrease of the TSI is not supported by the 2 models (period 02.02.2019 – 15.05.2019).
Outliers: none

2.2.12 TIM on TSIS-1

TIM on TSIS-1

Full name: Total Irradiance Monitor on TSIS

Organization: Laboratory for Atmospheric and Space Physics

Period covered

C3S period selected

adjustment factor

11.01.2018 – present

0.999535

Data availability

Data availability (gap filled)

C3S estimated noise level

86.30%

86.30% (100%)

0.076 W/m²

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	figure15
	figure15

Image Modified

Figure 15: (rescaled) TIM/TSIS-1 timeseries (green and orange) with C3S CDR (black) and NRLTSI2 (brown) models.

DATA SOURCE: http://lasp.colorado.edu/data/tsis/tsi_data/tsis_tsi_L3_c24h_latest.txt (version 4 is used)

References : Kopp (2020)

Notes:

Good agreement with the NRLTSI2 model, but apparent increase with respect to SATIRE-S
The TIM/TCTE is providing near real time data with a latency of about 5 days.
Outliers : none.

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section3
section3
3. Algorithms

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section3-1
section3-1
3.1 Radiometric correction factors

...

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	table2
	table2

Table 2 : Scaling factors and precision estimates (see Section 3.2) for the 12 input TSI timeseries.

 Mathinline
i

Instruments

Scaling factor

Mathinline
α_i

(unitless)

Precision

Mathinline
ε_i

(W/m²)

1

ERB/NIMBUS7

0.992447

318

2

ACRIM1

0.995568

270

3

ERBS

0.997149

(0.039) 0.270

4

ACRIM2

0.997821

215

5

DIARAD/VIRGO

0.996449

121

6

PMO06/VIRGO

1.000181

173

7

ACRIM3

1.000078

126

8

TIM/SORCE

1.000256

89

9

SOVA/PICARD

0.999345

145

10

PREMOS/PICARD

1.000256

86

11

TIM/TCTE

0.999771

92

12

TIM/TSIS-1

0.999535

76

S

SATIRE-S in 1979-1980

1.000150

-

Figure 16 shows the resulting scaled TSI records for the individual instruments. For clarity we use a 121-days running mean to remove the short term solar noise, and to highlight the instrumental differences. After scaling, the instruments agree in general quite well, except at the very beginning of the record and for 2018 onward. Figure 16 also shows that the ERBS instrument is critical to fill the so-called ACRIM gap (15.07.1989 – 03.10.1991), it is the only TSI instrument that was monitoring the TSI during this period.

...

As some instruments (PREMOS and SOVAP) have not observed during low activity periods, it is decided to use the ‘RMS max’ column as an estimation of the instrument precision. For the ERBS timeseries, the estimated precision is not realistic (due to the use of SATIRE-S in the gap filling). It is then decided to use the ACRIM1 precision as estimate for the ERBS record, as both missions used the same radiometric cavity.

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	table3
	table3

Table 3: Instrument precision estimated as root mean square (RMS) difference with SATIRE-S. The columns 'max' and 'min' correspond respectively to periods of high and low solar activity. The column ‘all’ does not involve any selection based on solar activity.

 Mathinline
i

Instruments

RMS max

RMS all

RMS min

1

ERB/NIMBUS7

0.318

0.270

0.263

2

ACRIM1

0.270

0.184

0.128

3

ERBS

(0.039) 0.270

(0.037) 0.184

(0.035) 0.128

4

ACRIM2

0.215

0.187

0.139

5

DIARAD/VIRGO

0.121

0.103

0.064

6

PMO06/VIRGO

0.173

0.142

0.079

7

ACRIM3

0.126

0.111

0.064

8

TIM/SORCE

0.089

0.071

0.035

9

SOVA/PICARD

0.145

-

10

PREMOS/PICARD

0.086

-

11

TIM/TCTE

0.092

0.073

0.039

12

TIM/TSIS-1

0.076

0.057

0.031

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section3-3
section3-3
3.3 Gap filling

Many of the input records have gaps in the daily TSI values. It is the case with the ERB (Nimbus7) and ERBS (ERBE) measurements at the beginning of the composite and also of the TSIS-1 instrument at the end of the composite. In the C3S v3.0 and v3.1 daily TSI composite, a gap filling mechanism is implemented as a preprocessing of the original timeseries. A gap is filled provided it extends over less than 50 days.

...

Anchor

	table4
	table4

Table 4: General characteristics of the C3S daily TSI composite CDR.

General characteristics of the CDR
Temporal resolution	daily mean
Time period	CDR v3.0: 1^st January 1979 to 31^st of December 2020 ICDR: 1^st January 2021 onward v3.1: 1^st January 2021 – 30^th September 2023
Format	ASCII
Filenames	C3S_RMIB_daily_TSI_composite_TCDR_v3.0.txt C3S_RMIB_daily_TSI_composite_ICDR_v3.1.txt

The Total Solar Irradiance is the spectrally integrated total amount of radiant energy coming from the Sun per square meter of surface, perpendicular to the sunlight, at 1 astronomical unit.

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	table5
	table5

Table 5: Total Solar Irradiance parameter.

Total Solar Irradiance
long_name	Total Solar Irradiance, daily Means
standard_name	Total Solar Irradiance
CF_name	solar_irradiance
units	W/m².

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references
references
References

Chapman, G. A., Cookson, A. M., and Dobias, J. J. (1996): Variations in total solar irradiance during solar cycle 22, J. Geophys. Res., 101(A6), 13541– 13548, https://www.doi.org/10.1029/96JA00683.

...

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section2
2. Input and auxiliary data

2.1.1 SATIRE-S

2.1.2 NRLTSI2

2.1.3 SATIRE-S / NRLTSI2 intercomparison

2.2.1 ERB on NIMBUS7

2.2.2 ACRIM1 on SMM

2.2.3 ERBS

2.2.4 ACRIM2

ACRIM2

2.2.5 DIARAD / VIRGO on SOHO

DIARAD / VIRGO on SOHO

2.2.6 PMO06 on VIRGO

PMO06 on VIRGO

2.2.7 ACRIM3

ACRIM3

2.2.8 TIM on SORCE

TIM on SORCE

2.2.9 SOVA on Picard

SOVA on Picard

2.2.10 PREMOS on Picard

PREMOS on Picard

2.2.11 TIM on TCTE

TIM on TCTE

2.2.12 TIM on TSIS-1

TIM on TSIS-1

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section3
3. Algorithms

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section3-1
3.1 Radiometric correction factors

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section3-3
3.3 Gap filling

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Anchorsection2section22. Input and auxiliary data

2.1.1 SATIRE-S

2.1.2 NRLTSI2

2.1.3 SATIRE-S / NRLTSI2 intercomparison

2.2.1 ERB on NIMBUS7

2.2.2 ACRIM1 on SMM

2.2.3 ERBS

2.2.4 ACRIM2

ACRIM2

2.2.5 DIARAD / VIRGO on SOHO

DIARAD / VIRGO on SOHO

2.2.6 PMO06 on VIRGO

PMO06 on VIRGO

2.2.7 ACRIM3

ACRIM3

2.2.8 TIM on SORCE

TIM on SORCE

2.2.9 SOVA on Picard

SOVA on Picard

2.2.10 PREMOS on Picard

PREMOS on Picard

2.2.11 TIM on TCTE

TIM on TCTE

2.2.12 TIM on TSIS-1

TIM on TSIS-1

Anchorsection3section33. Algorithms

Anchorsection3-1section3-13.1 Radiometric correction factors

Anchorsection3-3section3-33.3 Gap filling

AnchorreferencesreferencesReferences

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section2
2. Input and auxiliary data

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section3
3. Algorithms

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section3-1
3.1 Radiometric correction factors

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section3-3
section3-3
3.3 Gap filling

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References