Using IR Brightness Temperature Spectra to Disentangle the Effects of Ozone, Carbon Dioxide, and Water Vapor On Global Stratospheric Temperature Trends

The CLARREO mission has been established by NASA’s Langley Research Center to establish benchmark measurements using traceable international standards (SI) through various independent paths. Time standard, temperature standard, and solar/lunar standard are used to ensure unbiased and simple processing methods, rendering the claims of atmospheric trends irrefutable.

The objective of this study is to interpret the infrared brightness temperature spectra time series using coincident vertical profiles of stratospheric carbon dioxide, water vapor, and ozone concentration. Possible implications of this work could lead to disentangling a correlation between carbon dioxide and ozone. The trends in ozone may mask the effects of carbon dioxide. An increase in carbon dioxide causes a cooling effect in the stratosphere whereas ozone recovery should lead to a warming of the stratosphere. An increase in water vapor could lead to a decrease in ozone due to the changes in the catalytic chlorine/bromine free radical chemistry of the lower stratosphere.

The satellite observations used in this study are from a series of hyperspectral infrared sounders developed for the operational assimilation into numerical weather prediction models (NWP). These observations include the EUMETSAT METOP satellite series with the IASI sensor with data record beginning in January 2007 and the NASA/NOAA Suomi-NPP satellite with the CrIS and OMPS sensors with data record beginning in April 2012. The ozone profile observations were obtained from the OMPS Limb Profiler.

Previous findings (Brindley et al. 2015) imply that at the largest spatial scales, fluctuations in the mid to upper tropospheric temperatures and water vapor, and not cloud or surface temperature, play the dominant role in determining the level of interannual variability in all sky outgoing longwave radiation.  Enhanced variability was seen in the 9.6 micron ozone band.  In this study, we will investigate the role of ozone heating and carbon dioxide cooling on the observed brightness temperature spectra. In particular, the CrIS IR brightness temperatures will be correlated with ozone concentration at the corresponding height level. Similar analyses will be performed on carbon dioxide and water vapor. By doing so, this work is expected to lead to a better interpretation of climate trends in observed brightness temperature from missions such as the NASA CLARREO IR Pathfinder.