In
the present study atmospheric CO2 retrievals based on Aqua satellite
AIRS (Atmospheric Infrared
Sounder) instrument observations are compared with forward model predictions.
There is quite good agreement in seasonal cycles as well as North-South
gradients when averaged over large scales. At smaller scales there are
contrasts between upper troposphere CO2 above continents versus
oceans in the retrievals and there are signatures off Africa
which seem likely artifacts caused by aerosols. As a consequence retrievals
cannot be used at this stage to constrain surface sources and sinks without
causing large biases. Interestingly there is good agreement in the shape of the
N-S gradient at low-to-mid latitudes in the Northern hemisphere between
simulations based on one transport model (LMDZ) and retrievals, but disagreement
when comparing with simulations based on a second transport model (TM3). This
raises questions about lower to upper troposphere transport and their
representation in these models.
Author: Y. Tiwari, M. Gloor, R. Engelen, C. Rödenbeck, et al (ktiwari at bgc-jena dot mpg dot de)
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