Carbon Monoxide (CO) and Solar Cycle Variability
Jae N. Lee [Jae.N.Lee@nasa.gov], Joint Center for Earth Systems Technology, University
of Maryland, Baltimore County, Baltimore, MD; and NASA Goddard Space Flight Center,
Greenbelt, MD
To understand the temporal variability of the mesospheric Carbon Monoxide (CO)
composition in the wintertime polar middle atmosphere and its relation to the solar
variability, we analyze the CO observed with the Aura Microwave Limb Sounder (MLS).
The mesospheric CO is mainly produced by the Carbon Dioxide (CO2) photolysis and
can be considered as a tracer for the influence of the solar irradiance variability on the
mesosphere. We extract the solar signal from Aura MLS CO during December 2004 to
December 2011 period, in conjunction with Solar Radiation and Climate Experiment
(SORCE) measured total solar irradiance (TSI). We find that the positive correlation of
CO with the TSI is statistically significant up to 0.5 in the polar middle atmosphere in
both hemispheres. Positive correlation between TSI and CO indicates that increased
solar irradiance leads to abundant CO volume mixing ratio, by producing more CO by
photolysis of carbon dioxide in the upper mesosphere and thermosphere and transported
downward into the lower mesosphere and stratosphere. Positive correlation between TSI
and CO allows us to suggest that the interannual variability of the mesospheric CO and
the solar irradiance are physically connected.