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Published October 2012 | public
Journal Article

Fundamental modes of atmospheric CFC-11 from empirical mode decomposition

Abstract

Following an initial growth, the concentrations of chlorofluorocarbon-11 (CFC-11) in the atmosphere started to decline in the 1990's due to world-wide legislative control on emissions. The amplitude of the annual cycle of CFC-11 was much larger in the earlier period compared with that in the later period. We apply here the Ensemble Empirical Mode Decomposition (EEMD) analysis to the CFC-11 data obtained by the U.S. National Oceanic and Atmospheric Administration. The sum of the second and third intrinsic mode functions (IMFs) represents the annual cycle, which shows that the annual cycle of CFC-11 has varied by a factor of 2–3 from the mid-1970's to the present over polar regions. The results provide an illustration of the power of the EEMD method in extracting a variable annual cycle from data dominated by increasing and decreasing trends. Finally, we compare the annual cycle obtained by the EEMD analysis to that obtained using conventional methods such as Fourier transforms and running averages.

Additional Information

© 2014 World Scientific Publishing Company. Received 27 July 2012; Revised 30 September 2012; Accepted 12 November 2012; Published 26 March 2013. KFL performed the linear filtering analysis using the computer facilities at the Atomic and Molecular Physics Laboratories, The Australian National University provided by Dr. Franklin P. Mills. This research was supported by NSF grant ATM-9903790 to the California Institute of Technology. The CFC-11 data measured by the Halocarbons and other Atmospheric Trace Species (HATS) group were obtained from http://www.esrl.noaa.gov/gmd/hats/combined/CFC11.html.

Additional details

Created:
August 22, 2023
Modified:
October 17, 2023