GSB 7.1 Standardlösung

CM SAF: Top of atmosphere radiation

To understand the evolution of the Earth climate, it is essential to quantify the Earth Radiative Budget, i.e how much energy is coming in and how much is going out. The term 'how much is coming in' is given by the TOA Incoming Solar radiation (TIS). The term "how much is going out" is splitted in two parts the TRS and the TET, also respectively called short and longwave.

TOA Incoming Solar radiation (TIS)
The product is based on measurement of the Total Solar Irradiance (TSI, about 1362.5 W/m²) provided by the Differential Absolute Radiometer (DIARAD) instrument as part of the Variability of Irradiance and Gravity Oscillations (VIRGO) experiment on the Solar and Heliospheric Observatory (SOHO) satellite. By principle, differential radiometry allows to correct the temporal degradation of the instrument. As validation, the time series is regularly compared with time series from 3 others instruments (PMO6 VIRGO on SOHO, TIM on SORCE and ACRIM-3) as well as a time series taking as input solar magnetograms (a model allows to explain TSI as a function of sun magnetic activity). The methodology and results are presented by Mekaoui and Dewitte (2008). Such intercomparison exercise is regularly, i.e. about yearly, performed to incorporate the newly acquired data. Although there is no more concern about the stability of the data record, it is worth to precise that investigations are on-going about the absolute level of the TSI. A team has been set up by the International Space Science Institute to work on this topic. This ISSI initiative is known as "An Assessment of the Accuracies and Uncertainties in the Total Solar Irradiance Climate Data Record" and may result in an adjustment of the data record in the future.
Ref.: S. Mekaoui, S. Dewitte, 2008: Total Solar Irradiance Measurement and Modelling during Cycle 23, Solar Physics, Volume 247, Issue 1, pp 203-216

The TOA Reflected Solar (TRS) radiation corresponds to the energy reflected by the Earth system while the TOA Emitted Thermal (TET) radiation corresponds to the energy thermally emitted (TET is also often calles OLR as "Outgoing Longwave Radiation").

The CM SAF provides 2 distinct data records of TOA radiation products: a first one is based on the operational observations provided by the Meteosat First and Second Generation satellites. This record covers 1983-2015
(DOI: 10/5676/EUM_SAF_CM/TOA_MET/V001).
A second record exploits the enhanced possibilities offered by the MSG satellites, in particular the use of the GERB broadband instruments on MSG, covering 2004-2015
(DOI: 10/5676/EUM_SAF_CM/TOA_GERB/V002).

The TOA radiation products are provided as different temporal averages: monthly mean , daily mean, and monthly mean diurnal cycle.

Further details on the products in general, on retrieval details and physical basis as well as on quality can be found in the Product user Manuals (PUM), Algorithm Theoretical Basis Documents (ATBD) and the Validation Reports (ValRep).
All products can be ordered via the Web User Interface.

NC / Sep2018

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