Global Distribution of CO2 Volume Mixing Ratio in the Mesosphere and Lower Thermosphere and Long-Term Changes Observed By Saber
Thursday, 18 December 2014: 1:55 PM
The SABER 10-channel limb scanning radiometer has been operating onboard the TIMED satellite nearly continuously since launch on December 7, 2001. Beginning in late January, 2002 and continuing to the present day, SABER has been measuring limb radiance profiles used to retrieve vertical profiles of temperature, volume mixing ratios (VMRs) of O3, CO2, H2O, [O], and [H], and volume emission rates of NO, OH(2.1µm), OH(1.6µm) and O2(singlet delta). The measurements extend from the tropopause to the lower thermosphere, and span from 54S to 84N or 54N to 84S daily with alternating latitude coverage every ~ 60 days. Currently more than six million profiles of each parameter have been retrieved. The CO2 VMR is a new SABER data product that just became available this year. The temperature and CO2 VMRs are simultaneously retrieved in the ~65 km to 110 km range using limb radiances measured at 4.3 and 15 micrometers. Results will be presented of CO2 validation studies done using comparisons with coincident ACE-FTS CO2 data and SD-WACCM model simulations. The CO2 VMRs agree with ACE-FTS observations to within reported measurement uncertainties and they are in good agreement with SD-WACCM seasonal and global distributions. The SABER observed CO2 VMR departure from uniform mixing tends to start above ~80 km which is generally higher than what the model calculates. Variations of CO2 VMR with latitude and season are substantial. Seasonal zonal mean cross sections and CO2 time series for selected latitudes and altitudes over the 12.5-year time period, will also be shown. The CO2 VMR increase rate at 100 km is in close agreement with in situ results measured at the Mauna Loa Observatory.