CO2 semiannual oscillation in the middle troposphere and at the surface
Article first published online: 28 JUL 2012
©2012. American Geophysical Union. All Rights Reserved.
Global Biogeochemical Cycles
Volume 26, Issue 3, September 2012
How to Cite
2012), CO2 semiannual oscillation in the middle troposphere and at the surface, Global Biogeochem. Cycles, 26, GB3006, doi:10.1029/2011GB004118., , , , , , , and (
- Issue published online: 28 JUL 2012
- Article first published online: 28 JUL 2012
- Manuscript Accepted: 26 JUN 2012
- Manuscript Revised: 22 APR 2012
- Manuscript Received: 24 MAY 2011
- chemistry-transport model
 Using in situ measurements, we find a semiannual oscillation (SAO) in the midtropospheric and surface CO2. Chemistry transport models (2-D Caltech/JPL model, 3-D GEOS-Chem, and 3-D MOZART-2) are used to investigate possible sources for the SAO signal in the midtropospheric and surface CO2. From model sensitivity studies, it is revealed that the SAO signal in the midtropospheric CO2 originates mainly from surface CO2 with a small contribution from transport fields. It is also found that the source for the SAO signal in surface CO2 is mostly related to the CO2 exchange between the biosphere and the atmosphere. By comparing model CO2 with in situ CO2 measurements at the surface, we find that models are able to capture both annual and semiannual cycles well at the surface. Model simulations of the annual and semiannual cycles of CO2 in the tropical middle troposphere agree reasonably well with aircraft measurements.