"\"longwave\" means longwave radiation. Upwelling radiation is radiation from below. It does not mean \"net upward\". Radiance is the radiative flux in a particular direction, per unit of solid angle. The direction towards which it is going must be specified, for instance with a coordinate of zenith_angle. If the radiation does not depend on direction, a standard name of isotropic radiance should be chosen instead." . . . "Climate and Forecast (CF)" . "upwelling longwave radiance in air" . . .