Effect of line mixing on atmospheric brightness temperatures near 15 microm.

The effect of line mixing on the effective blackbody brightness temperature of the earth in the region of the 15microm nu (2)Q branch of CO(2) is calculated. The procedures used to compute line mixing follow those used to successfully model mixing observed in laboratory spectra of two near-infrared CO(2)Q branches. The atmospheric radiances are calculated between 664 and 670 cm(-1), a spectral region that is of interest for sounding the upper troposphere and the stratosphere. Mixing was found to lower the observed brightness temperatures by as much as 3 K for some temperature profiles. Ignoring this effect would significantly impact the ability of advanced sounders to produce temperature retrievals which meet the projected accuracy requirement of 1 K/km.