Improvements in Nimbus 7 limb infrared monitor of the stratosphere ozone profiles as obtained with updated spectral line parameters and radiance algorithms

Abstract

Ozone distributions from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) experiment of 1978–1979 are generally in good agreement with other concurrent ozone measurements in the middle and upper stratosphere, but not at lower altitudes. LIMS ozone is too large below about the 15‐hPa (or millibar) level, particularly at lower latitudes. A new LIMS ozone distribution is presented for 1 day of profiles, May 5, 1979, obtained with an improved forward radiance algorithm and using the spectral line parameters for the 9‐ to 10‐μm region in the HITRAN 92 compilation. However, we also divided our single day of retrieved ozone mixing ratio profiles by a suggested factor of 1.051, which makes them compatible with the ozone distributions from several of the UARS experiments. Our revised distribution still agrees with the archived LIMS ozone to better than ±5% above about the 15‐hPa level, but there is a significant decrease for the revised ozone in the lower stratosphere. That decrease approaches 25% at 50 hPa in the tropics. In general, the revised LIMS ozone is now in accord with the comparison data sets for the stratosphere, except for the lowest levels (Umkehr layer 3 or 63–127 hPa), where the effects of interfering species and small biases in LIMS temperatures are most pronounced. It is concluded that the current 9‐ to 10‐μm ozone line list is adequate for obtaining good quality ozone mixing ratio profiles from satellite broadband limb‐infrared measurements.