Rethinking satellite-based solar irradiance modelling: The SOLIS clear-sky module

TLDR: In this article, a new type of solar irradiance scheme is developed based on radiative transfer models (RTM) using atmospheric parameter information retrieved from the Meteosat Second Generation (MSG) satellite (clouds, ozone, water vapour) and the ERS-2/ENVISAT satellites (aerosols, ozone).

About: This article is published in Remote Sensing of Environment.The article was published on 2004-05-30 and is currently open access. It has received 263 citations till now. The article focuses on the topics: Solar irradiance & Atmospheric radiative transfer codes.

Figures

Fig. 13. Same as Fig. 12, but for global irradiance. Aerosol type is ‘‘maritime’’ on upper figure, and ‘‘urban’’ on lower figure.

Table 1 Improvements in METEOSAT resolution

Fig. 5. Correction of H2O deviations. The values derived with the MLB relation are compared for different H2O(g) amounts. H2O is specified in ppm (parts per million). Recalculation of the vertical optical depth leads to a good agreement between MLB values and the explicit RTM runs for the same ai.

Fig. 9. Comparison between SOLIS and measurements using the GADS/ OPAC information for the aerosols. The calculated Heliosat clear-sky irradiance is also diagrammed. The differences between the models are mainly due to the different atmospheric input information.

Fig. 3. For monochromatic radiation, the Lambert –Beer relation is still a good approximation if the ‘vertical’ optical depth s0 is used. In order to yield a better match, a correction of formula (2) (MLB relation) is necessary.

Fig. 2. Comparison between RTM calculations and fit using the modified Lambert–Beer relation for different atmospheric states.

Frequently asked questions

Q1. What are the contributions in "Rethinking satellite-based solar irradiance modelling the solis clear-sky module" ?

Within the European project Heliosat-3, a new type of solar irradiance scheme is developed. This paper focuses on the description of the clear-sky module of the new scheme, especially on the integrated use of a radiative transfer model. 

Q2. What future works have the authors mentioned in the paper "Rethinking satellite-based solar irradiance modelling the solis clear-sky module" ?

SOLIS provides the possibility to use enhanced information of the atmospheric state and, hence, the potential to improve the accuracy of the calculated direct, global, and diffuse irradiance. Additionally, spectrally resolved data can be calculated operationally in MSG pixel resolution. Deviations of the atmospheric state from the average ( O3, H2O ( g ), aerosols ) can be easily corrected using the results of the modified Lambert–Beer fit. The usage of the modified Lambert–Beer law enables not only the direct integration of an RTM into the irradiance scheme, but also the potential for the calculation and use of easy handling look-up tables. 

Q3. What are the benefits of the integrated use of RTM?

The integrated use of RTM is linked with high flexibility relating to the input of the atmospheric state, changes in theory (e.g., new aerosol models), and the desirable output parameters. 

Q4. What is the starting point of the integrated use?

Starting point of the integrated use is the assumption that daily values of the atmospheric clear-sky parameters in a spatial resolution of 100 100 or 50 50 km are sufficient. 

Q5. What is the importance of a accurate estimation of the downward solar irradiance?

An accurate estimation of the downward solar irradiance is not only of particular importance for assessing the radiative forcing of the climate system, but also absolutely necessary for an efficient planning and operation of solar energy systems and the estimation of the energy load. 

Q6. What is the way to obtain global ozone column maps?

The data assimilation approach delivers global ozone column maps for a certain point in time with a horizontal resolution of 0.36j. 

Q7. What is the way to use an RTM in the calculation schemes?

The integration of an RTM into the calculation schemes, instead of using precalculated lookup tables, is only possible if the necessary computing time can be decreased enormously. 

Q8. What is the problem with the use of an RTM for the treatment of heterogenous clouds?

With respect to 3-D cloud effects, an operational usage of an RTM for the treatment of heterogenous clouds (whether directly or using precalculated look-up tables) is not feasible today. 

Q9. What is the relative root mean square error for global and direct irradiance?

The relative root mean square error is 1.9% for global and 4.2% for direct irradiance with a relative bias of 0.6%and 0.5%, respectively. 

Q10. How can the aerosol optical depth be calculated?

With the knowledge of TL and w, and with the help of a model developed by Ineichen (2003), the aerosol optical depth can be retrieved.