LW upward 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.

The name of the parameter indicates all of the information about how the measurement was made. Refer to an overview.

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 “LW” or “longwave” energy. LW is infrared energy or heat, emitted by the Earth and atmosphere. This infrared light has wavelengths longer than about 5 micrometers.
This parameter is a measurement of Upward flux, or the emitted/reflected energy that’s going away from 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 infrared energy leaving the Earth system from the top of the atmosphere.