Net terrestrial radiation

From Glossary of Meteorology

net terrestrial radiation

(Also called net outgoing IR.) The net flux density of terrestrial radiation.

This is the difference between upwelling and downwelling longwave flux density, which may be referenced to any specified altitude, but is most commonly referenced to the surface. The long- term global average for the net terrestrial radiation leaving the earth's surface is approximately 50 W m-2.