Last modified on Jan 29, 2024 14:35

Contributors: A. Velazquez Blazquez (Royal Meteorological Institute of Belgium (RMIB)), N.Clerbaux (RMIB)

Issued by: RMIB/Nicolas Clerbaux

Date: 24/11/2023

Ref: C3S2_D312a_Lot1.2.2.6-v1.0_202303_PUGS_ECVEarthRadiationBudget_v1.1

Official reference number service contract: 2021/C3S2_312a_Lot1_DWD/SC1

History of modifications

List of datasets covered by this document

Related documents

Acronyms

List of tables

List of figures

General definitions

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).

Executive summary

The Total Solar Irradiance (TSI) quantifies the amount of solar energy that is received by the Earth. It is defined as the amount of solar power that reaches the Earth 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 an Essential Climate Variable (ECV) by the Global Climate Observing System (GCOS).

Within the Copernicus Climate Change Service (C3S), a long composite Climate Data Record (CDR) is constructed from different TSI measurements obtained by an ensemble of space instruments that have observed the Sun since the 1970’s. In the v3 version, the composite starts on 1/1/1979 and provides daily value of the TSI. To create the composite, the measurements of the individual instruments are first put on a common absolute scale, and their quality is assessed by intercomparison. Then, the composite time series is an average of all available measurements, on a daily basis.

Section 1 presents a description of the product, with the list of the instruments used in the generation of the datasets. In addition, there's all the information related to the format and requirements of the product, with an example of a dataset. Section 2 presents all the information related to the access of the data and the data sources.

1. Composite daily Total Solar Irradiance CDR

1.1 Product description

The Total Solar Irradiance (TSI) quantifies the amount of solar energy that is received by the Earth. The TSI is defined as the amount of solar power that reaches the Earth’s top of the atmosphere per unit surface area perpendicular to the Sun–Earth direction at the mean Sun–Earth distance. It is a fundamental variable governing the climate system, and is recognized as an ECV by the Global Climate Observing System (GCOS). Within the Copernicus Climate Change Service (C3S), a composite Climate Data Record (CDR) is constructed from measurements of the TSI assessed by an ensemble of space instruments.

The first Total Solar Irradiance (TSI) measurements from space were made with the Temperature Control Flux Monitor (TCFM) on Mariner 6 and 7 (Plamondon, 1969). Following this, continuous measurement of the TSI started with the Earth Radiation Budget (ERB) instrument on Nimbus 7 (Hickey et al., 1980). Then continuous monitoring with an ageing corrected TSI instrument started with the Active Cavity Radiometer Irradiance Monitor (ACRIM1) instrument on the Solar Maximum Mission (SMM) (Willson et al., 1980). Since these early missions, TSI measurements have been continued with several space instruments listed in Table 1-2 (reproduced from ATBD [D1]).

The daily TSI composite is constructed by scaling the individual series to a common absolute level as described in the ATBD [D1]. An important part is the definition of this reference level. In the version v3.0 (and the following ICDR releases v3.1, v3.2, etc), the scaling level is defined by normalizing a set of reference instruments, in such a way that their average scale factor is equal to 1. These reference instruments are indicated with a (*) in Table 1-2.

For the ICDR, a regular download of new TSI data is performed for the active instruments before launching the ICDR processing. Currently these active instruments are: DIARAD/VIRGO, PMO6/VIRGO and TIM/TSIS. This list is likely to change in the future due to probable discontinuation of the SOHO satellite (with DIARAD and PMO06 instruments onboard) and also the incorporation of new instruments like DARA and CLARA.

The general characteristics of this Climate Data Record (CDR) are summarized in Table 1-1.

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

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 (*).

Figure 1 illustrates the TSI daily timeseries. The daily values are shown in grey while the red curve shows the 121-days running mean. The CDR (indicated as TCDR on the graph) starts during the solar cycle 21 and stops just before the increase of solar activity during cycle 25. The ICDR (interim) period is shown.

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).

1.2 Target requirements

The target requirements for the TSI daily records are discussed in the Target Requirements and Gap Analysis Document (TRGAD)[D5] and are summarized in Table 1-3. The stability requirement is slightly relaxed for the ICDR version. These requirements are verified in the Product Quality Assurance Report (PQAR, [D5]).

Table 1-3: Target requirements for the C3S v3.x daily TSI CDR.

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.

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

The 9^th 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.

Table 1-5: Instrument flag code.

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 (Ball et al., 2014) 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 1^st January 1979 and 6 November 1980).

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

The users are invited to read the ATBD [D1], the PQAD [D2], the PQAR [D3], the SQAD [D4] and the TRGAD [D5] documents for additional information on the data product and production system. 

1.4 Disclaimer and License

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 License and disclaimer apply: https://cds.climate.copernicus.eu/api/v2/terms/static/licence-to-use-copernicus-products.pdf

2. Data access information

2.1 Data access through the RMIB

The C3S daily Total Solar Irradiance (TSI) timeseries is made available to the C3S Climate Data Store (CDS) through an HTTPS server hosted by the Royal Meteorological Institute of Belgium (RMIB). The server provides a validated version of the CDR over the period: 1^st January 1979 – 31^st December 2020 (in version 3.0):

        https://gerb.oma.be/tsi/C3S_RMIB_daily_TSI_composite_TCDR_v3.0.txt

and regularly updated the ICDR with increasing version number v3.x, e.g.:

        https://gerb.oma.be/tsi/C3S_RMIB_daily_TSI_composite_ICDR_v3.1.txt

In addition, a daily update of the ICDR is performed in the “latest” file:

        https://gerb.oma.be/tsi/C3S_RMIB_daily_TSI_composite_ICDR_v3_latest.txt

2.2 Data access through the CDS

Data access through the CDS

Within C3S, the distribution will be through the CDS (https://cds.climate.copernicus.eu/) where documentation created for the inclusion of the data in the CDS, such as this PUGS, will be also provided.

2.3 Product ordering process

You need to be registered and logged in to order products in the CDS. A login is provided upon registration, all products in the CDS are delivered free of charge.

References

Ball, W.T., Krivova, N.A., Unruh, Y.C., Haigh, J.D. and Solanki, S.K., 2014. A new SATIRE-S spectral solar irradiance reconstruction for solar cycles 21–23 and its implications for stratospheric ozone. Journal of the Atmospheric Sciences, 71(11), pp.4086-4101.

Crommelynck, D., Domingo, V., Fichot, A., & Lee, R. (1994). Total Solar Irradiance Observations from the EURECA and ATLAS Experiments. International Astronomical Union Colloquium, 143, 63-69. doi:10.1017/S0252921100024544

Dewitte S. (2013). The Contribution of the DIARAD Type Radiometer to the Revision of the Solar Constant Technical Note. Available at ftp://gerb.oma.be/steven/RMIB_TSI_composite/ diaradnewsolarconstant.pdf

Dewitte, S. and Clerbaux, N., 2017. Measurement of the earth radiation budget at the top of the atmosphere—a review. Remote Sensing, 9(11), p.1143.

Dewitte, S. and Nevens, S., 2016. The total solar irradiance climate data record. The Astrophysical Journal, 830(1), p.25.

Dewitte, S., Crommelynck, D., and Joukoff, A. (2004). Total solar irradiance observations from DIARAD/VIRGO, J. Geophys. Res., 109, A02102, doi:10.1029/2002JA009694.

Dewitte, S., Janssen, E. and Mekaoui, S., (2013). May. Science results from the Sova-Picard total solar irradiance instrument. In AIP Conference Proceedings (Vol. 1531, No. 1, pp. 688-691). AIP. doi:10.1063/1.4804863

ERBE Science Team (1986). First data from the Earth Radiation Budget Experiment. BAMS, 67, 818--824.

Froehlich, C. (2003). Long-Term Behaviour of Space Radiometers, Metrologia,40, 60-65.

Froehlich, C., Crommelynck, D.A., Wehrli, C. et al. (1997). In-Flight Performance of the Virgo Solar Irradiance Instruments on Soho. Sol. Phys. 175, 267–286. doi:10.1023/A:1004929108864

Hickey, J.R., L.L. Stowe, H. Jacobowitz, P. Pellegrino, R.H. Machhoff, F. House, T.H. Vonder Haar (1980). Initial solar irradiance determinations from nimbus 7 cavity radiometer measurements, Science, 208, 281--283.

Kopp, G., Lawrence, G. & Rottman, G. (2005). The Total Irradiance Monitor (TIM): Science Results. Sol Phys 230, 129–139. doi:10.1007/s11207-005-7433-9

Mekaoui, S., Dewitte, S. (2008). Total Solar Irradiance Measurement and Modelling during Cycle 23. Sol Phys 247, 203–216. doi:10.1007/s11207-007-9070-y

Mekaoui, S., Dewitte, S., Conscience, C. and Chevalier, A. (2010). Total solar irradiance absolute level from DIARAD/SOVIM on the International Space Station. Advances in Space Research, 45(11), pp.1393-1406.

Mount Wilson Observatory (2013). The 150-foot Solar Tower Current Selected Data (Mt. Wilson, CA: Mount Wilson Institute), http://obs.astro.ucla.edu/150_data.html

Plamondon, (1969): TCFM solar observations on Mariner 6, JPL Space Program Summary, 3, 162.

Romero, J., Wehrli, C. & Fröhlich, C. (1994). Solar total irradiance variability from SOVA 2 on board EURECA. Sol. Phys. 152, 23–29 doi:10.1007/BF01473178

Schmutz W., Fehlmann A., Finsterle W., Kopp G., Thuillier G. (2012). Total solar irradiance measurements with PREMOS/Picard, AIP Conf. Proc, 1531, 624. doi: 10.1063/1.4804847

TCTE 2014, Total Solar Irradiance Calibration Transfer Experiment (Boulder, CO: Univ. of Colorado), http://lasp.colorado.edu/home/tcte/data

Willson, R. (1994). Irradiance Observations of SMM, Spacelab 1, UARS, and ATLAS Experiments. International Astronomical Union Colloquium, 143, 54-62. doi:10.1017/S0252921100024532

Willson, R.C. (2014). ACRIM3 and the Total Solar Irradiance database. Astrophys. Space Sci. 352, 341–352. doi:10.1007/s10509-014-1961-4

Willson, R.C., S. Gulkis, M. Janssen, H.S. Hudson, G.A. Chapman, (1980): Observations of Solar Irradiance Variability, Science, 211, 700 - 702. doi: 10.1126/science.211.4483.700

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