Keywords:
ozone
;
stratosphere
Description / Table of Contents:
One of the largest uncertainties in determining the effect of CFC’s on stratospheric ozone has been the
magnitude of the trends in the altitude region between 15 and 20 km. In the 1994 WMO-UNEP ozone
assessment, SAGE was reported as giving trends up to -0± 8% per decade at northern mid-latitudes,
while the ozonesonde stations gave a trend of -± 3% per decade. In 1996 the SPARC panel on
Understanding Ozone Trends and the International Ozone Commission decided to collaborate, under the
auspices of the World Climate Research Programme and the World Meteorological Organisation, on a
study to carefully re-evaluate the ground-based and satellite data to resolve this discrepancy. The
philosophy of the study was similar to that of the International Ozone Trends Panel of 1988 which
addressed the total ozone measurements. The published literature was not simply reviewed, but a critical
re-analysis and interpretation of the vertical profiles of ozone was performed. One of the principal aims
of the report was to determine if there was sufficient confidence in the long-term measurement systems
to use them for accurate determination of ozone trends in the stratosphere and troposphere. A major
purpose of the study was to validate the quality of the data including quantification of the errors and to
determine if there were any limitations in altitude or latitude.
The report is divided into three main chapters. Chapter 1 contains a description of how the various
instruments work, and how ozone concentrations are calculated from the raw measurement. Particular
attention is paid to the true vertical resolution of each instrument’s measurement and to its long term
calibration drift as well as to its precision and accuracy. Chapter 2 assesses how well the various
measurements agree through a series of rigorous data comparisons. Traditional techniques based on zonal
averages and on close matches in time and space are augmented by new techniques which classify the air
mass according to its dynamic history. Chapter 3 discusses and uses the various methods available for
calculating trends, as well as investigating how well the causes of the trends can be determined by
statistical approaches.
Pages:
Online-Ressource (288 Seiten)
URL:
http://www.sparc-climate.org/publications/sparc-reports/sparc-report-no1/
Language:
English
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