Solar Radiation

EO Capability Benefits

Solar radiation is important for siting solar farms, as it informs energy yield estimations. Similarly, the Solar Potential of Buildings and energy-efficient building design rely on this variable. In agriculture, crop yield forecasting and evapotranspiration analysis require an accurate understanding of solar radiation. Finally, our climate and atmospheric dynamics are influenced by the sun’s radiation at a fundamental level.

EO Capability Description

Solar radiation is an umbrella term for a range of measurements and types of solar energy reaching the Earth. Solar irradiance, indicated in W/m², is the power per unit area received from the Sun in the form of electromagnetic radiation. Connected to this is solar insolation representing the total amount of solar energy received over a given period of time per unit area, commonly measured in kWh/m²/day (sometimes also called average irradiation). Different temporal units can be used, e.g. to derive monthly or annual averages.

Approaches typically combine data from geostationary (e.g. GOES, Meteosat) and polar-orbiting satellites (e.g. MODIS) with high temporal resolution, with sophisticated modelling techniques. Clear sky models are used to estimate solar surface irradiance under cloudless conditions, accounting for the Earth-Sun distance as well as the atmosphere’s composition (e.g. aerosols, water vapor and ozone) and the path length of radiation passing through the atmosphere depending on the Sun’s position. More complex models also account for local atmospheric variability, such as that caused by air pollution.

As Cloud Cover affects the amount of radiation reaching the Earth’s surface, satellite imagery is used to calculate the effective cloud albedo relative to clear-sky conditions, thus enabling all-sky irradiance to be estimated. This approach provides data for regions lacking ground-based measurements.

As higher altitudes receive more intense irradiance, Digital Elevation Models are also used to account for the effects of elevation on solar irradiance.

Indicative Cost Range Details

Various solar radiation-related global datasets at 0.05 degrees spatial resolution are available freely through EUMETSAT’s Satellite Application Facility on Climate Monitoring (CM SAF). Specialised companies offering end-to-end solutions tend to follow a subscription model.

Basic EO Capabilities

Cloud Cover

Operational Use

Digital Elevation Model

Operational Use

Relevant EO Technologies

BROAD-BAND RADIOMETERS

MULTI-PURPOSE VIS/IR

MR SPECTRO-RADIOMETERS

HR OPTICAL

Simple scanning telescopes that measure how much sunlight is reflected by Earth and how much heat the planet emits back to space, each in very wide spectral bands from visible light out into the thermal infrared. By measuring one band that only sees reflected sunlight and another that sees both sunlight and heat, they can subtract the two to work out just the heat component, then use models of how clouds and surfaces reflect and emit in different directions (helped by cloud images from instruments like MODIS, VIIRS or SEVIRI). Those raw measurements are turned into maps of energy flow at the top of the atmosphere. Spatial resolution ranges between 20–50 km.

EXAMPLES

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