Rethinking satellite-based solar irradiance modellingThe SOLIS clear-sky module

Abstract

Accurate solar irradiance data are not only of particular importance for the assessment of the radiative forcing of the climate system, but also absolutely necessary for efficient planning and operation of solar energy systems. Within the European project Heliosat-3, a new type of solar irradiance scheme is developed. This new type will be 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).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. The linkage of the clear-sky module with the cloud module is also briefly described in order to point out the benefits of the integrated RTM use for the all-sky situations. The integrated use of an RTM within the new Solar Irradiance Scheme SOLIS is applied by introducing a new fitting function called the modified Lambert -Beer (MLB) relation. Consequently, the modified Lambert -Beer relation and its role for an integrated RTM use are discussed. Comparisons of the calculated clear-sky irradiances with ground-based measurements and the current clear-sky module demonstrate the advantages and benefits of SOLIS. Since SOLIS can provide spectrally resolved irradiance data, it can be used for different applications. Beside improved information for the planning of solar energy systems, the calculation of photosynthetic active radiation, UV index, and illuminance is possible. D

A broadband simplified version of the Solis clear sky model

“…is a good fitting function for the horizontal global irradiance (Mueller et al, 2004). The source of the incoming diffuse irradiance is the attenuation of the beam radiation due to scattering process and it cannot be described in term of attenuation of the incoming radiation.…”

“…The Solis model (Mueller et al, 2004) was developed within the frame of the European project Heliosat-3 and is used as normalization function in the Meteosat satellite irradiance evaluation process. It is a spectrally resolved physical model, based on radiative transfer model (RTM) calculations, it needs atmospheric water vapor column and aerosol content as main input parameters.…”

“…The scheme is used to derive the radiation components from the GOES satellites in the US (George et al, 2007). (Mueller et al, 2004) The knowledge of the aerosol and water vapor content of the atmosphere makes evaluation of the clear sky irradiance possible with Solis, a model based on radiative transfer calculations. The basis of the model is the LambertBeer relation:…”

Conversion function between the Linke turbidity and the atmospheric water vapor and aerosol content

“…In order to extend its validity to higher atmospheric water vapor content and to introduce altitude dependence, a new formulation is proposed. It is based on a new clear sky model developed by Mueller et al (2004) derived from LibRadtran (Mayer et al, 1997) radiative transfer calculations: the Solis scheme. It is fully compatible with the above formulation within the specified limits.…”

A non-parametric method for correction of global radiation observations

“…With the statistical clear-sky model the sensor output level under clear-sky conditions is modeled directly from the observations. This is compared to solar radiation calculated with a clear-sky model based on physical modeling of the optical effects through the atmosphere, such as the models described by Davies and McKay (1982), Bird (1984), Rigollier et al (2000), Mueller et al (2004), andIneichen (2006). In the preset study forecasts from a numerical weather prediction (NWP) model is used.…”