Intercomparison of vertically resolved merged satellite ozone data sets: interannual variability and long-term trends
In the framework of the SI2N (SPARC (Stratosphere-troposphere Processes And their Role in Climate)/IO<sub>3</sub>C (International Ozone Commission)/IGACO-O3 (Integrated Global Atmospheric Chemistry Observations – Ozone)/NDACC (Network for the Detection of Atmospheric Composition Change))...
Main Authors: | , , , , , , , , , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2015-03-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | http://www.atmos-chem-phys.net/15/3021/2015/acp-15-3021-2015.pdf |
Summary: | In the framework of the SI2N (SPARC (Stratosphere-troposphere Processes And
their Role in Climate)/IO<sub>3</sub>C (International Ozone
Commission)/IGACO-O3 (Integrated Global Atmospheric Chemistry Observations – Ozone)/NDACC (Network for the Detection of Atmospheric Composition
Change)) initiative, several long-term vertically resolved merged ozone data
sets produced from satellite measurements have been analysed and compared.
This paper presents an overview of the methods, assumptions, and challenges
involved in constructing such merged data sets, as well as the first thorough
intercomparison of seven new long-term satellite data sets. The analysis
focuses on the representation of the annual cycle, interannual variability,
and long-term trends for the period 1984–2011, which is common to all data
sets. Overall, the best agreement amongst data sets is seen in the
mid-latitude lower and middle stratosphere, with larger differences in the
equatorial lower stratosphere and the upper stratosphere globally. In most
cases, differences in the choice of underlying instrument records that were
merged produced larger differences between data sets than the use of
different merging techniques. Long-term ozone trends were calculated for the
period 1984–2011 using a piecewise linear regression with a change in trend
prescribed at the end of 1997. For the 1984–1997 period, trends tend to be
most similar between data sets (with largest negative trends ranging from −4
to −8% decade<sup>−1</sup> in the mid-latitude upper stratosphere), in large part due to
the fact that most data sets are predominantly (or only) based on the SAGE-II
record. Trends in the middle and lower stratosphere are much smaller, and,
particularly for the lower stratosphere, large uncertainties remain. For the
later period (1998–2011), trends vary to a greater extent, ranging from
approximately −1 to +5% decade<sup>−1</sup> in the upper stratosphere. Again, middle and
lower stratospheric trends are smaller and for most data sets not
significantly different from zero. Overall, however, there is a clear shift
from mostly negative to mostly positive trends between the two periods over
much of the profile. |
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ISSN: | 1680-7316 1680-7324 |