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Figure 1-1: Illustration of the C3S daily TSI CDR (v3.0) and ICDR period (1/1/2021 onward), in grey. The 121-days running mean is also shown (orange curve).

Figure 1-2: Beginning of the C3S TSI data file.

General definitions

Term

Definition

Total Solar Irradiance (TSI)

The Total Solar Irradiance (TSI) quantifies the total amount of solar energy that is received by the Earth. It is defined per unit surface perpendicular to the Sun–Earth direction at the mean Sun–Earth distance. The TSI is a fundamental variable governing the climate system, and is recognized as Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS).

Climate Data Store (CDS)

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

Earth Radiation Budget

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.

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

An interim CDRs is an extension of a CDR that meets some timeliness requirements needed in some applications (e.g. “State of the Climate” reports). These preliminary data might not be fully validated and may need to be reprocessed before inclusion in the CDR.

Astronomical unit

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 (usually expressed in W/m² unit).

Scope of the document

This document is the Product User Guide and Specifications (PUGS) for the third version (v3.0) of the daily Total Solar Irradiance (TSI) timeseries which is generated and published as part of the Copernicus Climate Change Service (C3S), and subsequent ICDR extensions of the product time series (v3.x). It provides the minimum information a user should need for an appropriate use of the TSI data available through the C3S Climate Data Store (CDS).

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table1_1
Table 1-1: General characteristics of the C3S v3.x daily TSI CDR.

C3S daily TSI timeseries

Spatial resolution

NA

Grid

NA

Temporal resolution

Daily mean

Time period

CDR : 1st Jan. 1979 to 31st Dec. 2020

ICDR : 1st Jan. 2021 to present

(~ 10 days latency)

Format

ASCII

Reference level for the fluxes

Irradiance at 1 Astronomical Unit (AU)

+ Irradiance at actual Earth-Sun distance


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Table 1-2: Total Solar Irradiance space instruments (the acronyms are defined in footnote). The instruments used in the C3S v3.x composite are indicated in bold while the 5 instruments used to define the absolute level are marked with (*).

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)

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)

NOAA-9

Yes

1985 - 1989

ERBE(1986)

ACRIM 2

UARS

Yes

1991 - 2001

Willson et al. (1994)

Solcon 2

Atlas 1

No

1992

Crommelynck et al (1994)

Sova 1

Eureca

No

1992 - 1993

Crommelynck et al (1994)

Sova 2

Eureca

No

1992 - 1993

Romero et al. (1994)

ISP-2

Meteor-3 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. (2012)

PREMOS (*)

Picard

Yes

2010 - 2014

Schmutz et al. (2012)

SIM

FY 3B

No

2011 - present

Fang et al. (2014)

TIM (*)

TCTE

Yes

2013 - present

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



Info
iconfalse

1 TCFM: Temperature Control Flux Monitor; ERB: Earth Radiation Budget; ACRIM: Active Cavity Radiomer 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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table1_3
Table 1-3: Target requirements for the C3S v3.x daily TSI CDR.

Target requirements

Spatial resolution

NA

Temporal coverage

1st January 1979 - present

Accuracy

TCDR : < 1 W/m²
ICDR : < 1 W/m²

Stability

TCDR : < 0.3 W/m²/decade
ICDR : < 0.5 W/m²/decade

1.3 Data Format

The data comes as a simple ASCII text file that can be opened with many tools such as text editors (e.g. vi, gedit, notepad, etc.), spreadsheets (e.g. excel), and graphical tools (e.g. gnuplot). It contains a header followed by the actual data. The header provides information about the CDR such as the version, type (CDR or ICDR), creation date and time, license, documentation, input time series (instruments) that have been used, and scaling factors. Any user of the data should have a careful look at the header. The data part is organized per line, with 1 line per day, with 23 columns with the content specified in Table 1-4.

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Table 1-4: Data format per column of the C3S v3.x daily TSI CDR.

col

Column content
1

Date expressed as fractional year (e.g. 1987.0 is 1st Jan 1987 at 00:00 UTC). This field is useful for visualization.

2

Total Solar Irradiance (TSI) value in W/m² at 1 Astronomical Unit (AU). This value is the daily mean.

3

Date expressed as Julian Day number (integer number).

4

Date expressed as a character string YYYYMMDD (YYYY=year, MM=month, DD=day)

5

Number of individual TSI values combined in the composite TSI for this day.

6

Estimated TSI uncertainty in W/m².

7

Earth-Sun distance in Astronomical Unit (AU) for this date at 12:00 UTC.

8

TSI value at the actual Earth-Sun distance, in W/m².

9

Flags for the instruments/models used in the composite.

10

Original TSI values for instrument ERB/NIMBUS7

11

Original TSI values for instrument ACRIM1

12

Original TSI values for instrument ERBS

13

Original TSI values for instrument ACRIM2

14

Original TSI values for instrument DIARAD/VIRGO

15

Original TSI values for instrument PMO06/VIRGO

16

Original TSI values for instrument ACRIM3

17

Original TSI values for instrument TIM/SORCE

18

Original TSI values for instrument PREMOS

19

Original TSI values for instrument SOVAP

20

Original TSI values for instrument TIM/TCTE

21

Original TSI values for instrument TIM/TSIS1

22

Original TSI values for model SATIRE

23

Original TSI values for model NRLTSI2

The 9th column provides a character string composed of 14 digits, one for each instrument/model used in the composite. The order of these digits follows the order in the table. The meaning of each digit is presented in table 1-5. As an example, the character string “02030000000011” means that only instruments 2 and 4 are used for the daily mean for this particular day.

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table1_5
Table 1-5: Instrument flag code.

Instrument flag code

0

No data available for this day. The value in the instrument column is “NaN”.

1

Data available for this day, but not used in the composite. The non-used value is in the instrument column.

2

Data available for this day and used in the composite. The non-used value is in the instrument column.

3

Data are not available for this day but interpolation is done. The interpolated value is given in the instrument’s column.

4

Data rejected for this day (e.g. outlier), interpolation is done. The original value is given in the instrument’s column.

The following figure 1-2 shows the beginning of the C3S TSI data file. The two last columns provide the TSI value from the SATIRE-S (Yeo et al, 2014a and 2014b) and the NRL TSI v2 semi-empirical models. These models are not used in the CDR, except SATIRE-S at the very beginning of the record (between 1st January 1979 and 6 November 1980).

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This data product has been produced by the Royal Meteorological Institute of Belgium (RMIB), on behalf of the Copernicus Climate Change Service (C3S). The following relevant License and disclaimer apply: https://cds.climate.copernicus.eu/api/v2/terms/static/licence-to-use-copernicus-products.pdf

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section2
2. Data access information

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