SW downward flux is part of Earth’s energy budget. This concept is used to understand how much energy the Earth gets from the Sun, and how much energy the Earth system radiates back to outer space. All energy budget parameters describe the ‘flux,’ or flow, of a specific type of electromagnetic energy.
This parameter is reported on a 72-Day cycle and is an average value for that 72-day period.
This parameter is a TOA measurement, meaning that it’s measured at the top of the atmosphere. For the purposes of Earth’s radiation budget, TOA is considered to be about 20 km above the surface of the Earth. Above that there is little interaction between the energy flux and the atmosphere.
Because this is an All-sky parameter, it includes all types of conditions, including clear or cloudy skies when they occur.
It specifically measures ‘SW’ or ‘shortwave’ energy. SW is visible light, emitted by the Sun and then reflected or absorbed by the Earth and Earth’s atmosphere. This visible light has wavelengths shorter than 5 micrometers.
This parameter is a measurement of Downward flux, or the energy that’s coming toward the Earth.
Flux is the rate of energy flow coming in or out. In other words, flux measures how much energy is coming or going.
Overall, this parameter measures the amount of visible light energy entering the Earth system at the top of the atmosphere.