Global CFC-11 (CCl3F) and CFC-12 (CCl2F2) measurements with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS): retrieval, climatologies and trends 1Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK), Karlsruhe, Germany
17 Dec 2012
2Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain
3NOAA Earth System Research Laboratory, Boulder, CO 80305, USA
4Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA
Received: 11 Jun 2012 – Published in Atmos. Chem. Phys. Discuss.: 25 Jul 2012Abstract. Vertical profiles of CFC-11 (CCl3F) and CFC-12 (CCl2F2) have been
measured with the Michelson Interferometer for Passive Atmospheric Sounding
(MIPAS) with global coverage under daytime and nighttime conditions. The
profile retrieval is based on constrained nonlinear least squares fitting of
measured limb spectral radiance to modeled spectra. CFC-11 is
measured in its ν4-band at 850 cm−1, and CFC-12 is analyzed in its
ν6-band at 922 cm−1. To stabilize the retrievals, a Tikhonov-type
smoothing constraint is applied. Main retrieval error sources are measurement
noise and elevation pointing uncertainties. The estimated CFC-11 retrieval
errors including noise and parameter
errors but excluding spectroscopic data uncertainties are below 10 pptv
in the middle stratosphere,
depending on altitude, the MIPAS measurement mode and the actual atmospheric
situation. For CFC-12 the total retrieval errors are below 28 pptv at an
altitude resolution varying from 3 to 5 km.
Time series of altitude/latitude bins were fitted by a simple parametric
approach including constant and linear terms, a quasi-biennial oscillation
(QBO) proxy and sine and cosine terms of several periods.
In the time series from 2002 to
2011, quasi-biennial and annual oscillations are clearly visible.
A decrease of stratospheric CFC mixing ratios in response to the Montreal
Protocol is observed for most altitudes and latitudes. However, the trends
differ from the trends measured in the troposphere, they are even positive at some
latitudes and altitudes, and can in some cases only be explained by decadal
changes in atmospheric age of air spectra or vertical mixing patterns.
Revised: 29 Nov 2012 – Accepted: 03 Dec 2012 – Published: 17 Dec 2012
Citation: Kellmann, S., von Clarmann, T., Stiller, G. P., Eckert, E., Glatthor, N., Höpfner, M., Kiefer, M., Orphal, J., Funke, B., Grabowski, U., Linden, A., Dutton, G. S., and Elkins, J. W.: Global CFC-11 (CCl3F) and CFC-12 (CCl2F2) measurements with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS): retrieval, climatologies and trends, Atmos. Chem. Phys., 12, 11857-11875, doi:10.5194/acp-12-11857-2012, 2012.