Interrelated variations of O3, CO and deep convection in the tropical/subtropical upper troposphere observed by the Aura Microwave Limb Sounder (MLS) during 2004–2011 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
17 Jan 2013
2School of Engineering and Applied Sciences, Harvard University, Cambridge, USA
3School of GeoSciences, The University of Edinburgh, Edinburgh, UK
Received: 24 May 2012 – Published in Atmos. Chem. Phys. Discuss.: 31 Jul 2012Abstract. The interrelated geographic and temporal variability seen in more
than seven years of tropical and subtropical upper tropospheric
(215 hPa) ozone, carbon monoxide and cloud ice water content (IWC)
observations by the Aura Microwave Limb Sounder (MLS) are presented.
Observed ozone abundances and their variability (geographic and
temporal) agree to within 10–15 ppbv with records from sonde
observations. MLS complements these (and other) observations with
global coverage and simultaneous measurements of related parameters.
Previously-reported phenomena such as the ozone "wave one" feature
are clearly seen in the MLS observations, as is a double peak in
ozone abundance over tropical East Africa, with enhanced abundances
in both May to June and September to November. While repeatable
seasonal cycles are seen in many regions, they are often accompanied
by significant interannual variability. Ozone seasonal cycles in
the southern tropics and subtropics tend to be more distinct (i.e.,
annually repeatable) than in the northern. By contrast, carbon
monoxide shows distinct seasonal cycles in many northern subtropical
regions, notably from India to the Eastern Pacific. Deep convection
(as indicated by large values of IWC) is typically associated with
reductions in upper tropospheric ozone. Convection over polluted
regions is seen to significantly enhance upper tropospheric carbon
monoxide. While some regions show statistically significant
correlations among ozone, carbon monoxide and IWC, simple
correlations fall well short of accounting for the observed
variability. The observed interrelated variations and metrics of
annual and interannual variability described here represent a new
resource for validation of atmospheric chemistry models.
Revised: 25 Nov 2012 – Accepted: 13 Dec 2012 – Published: 17 Jan 2013
Citation: Livesey, N. J., Logan, J. A., Santee, M. L., Waters, J. W., Doherty, R. M., Read, W. G., Froidevaux, L., and Jiang, J. H.: Interrelated variations of O3, CO and deep convection in the tropical/subtropical upper troposphere observed by the Aura Microwave Limb Sounder (MLS) during 2004–2011, Atmos. Chem. Phys., 13, 579-598, doi:10.5194/acp-13-579-2013, 2013.