Classification of Ascension Island and Natal ozonesondes using self-organizing maps

Anders A. Jensen, Anne Mee Thompson, F. J. Schmidlin

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Ozone profiles from balloon-borne ozonesondes are used for development of satellite algorithms and in chemistry-climate model initialization, assimilation and evaluation. An important issue in the application of these profiles is how best to treat variations where varying photochemical and dynamical influences can cause the ozone mixing ratio in the tropospheric segments of the profile to change by of a factor of 2-3 within a day. Clustering techniques are an ideal way to approach the statistical classification of profile data and we apply self-organizing maps to tropical tropospheric SHADOZ data, hypothesizing that the data will sort according to various influences on ozone, namely anthropogenic sources like biomass burning, meteorological conditions, and stratospheric or extra-tropical intrusions. Self-organizing maps, that use a learning algorithm to reveal the most prominent features of a data set according to a specified number of clusters, have been determined for the 1998-2009 SHADOZ profiles over Ascension Island (512 profiles, 7.98S, 14.42W) and Natal, Brazil (425 profiles, 5.42S, 35.38W). The 2×2 self-organizing map, which creates 4 clusters, reveals that deviations from the average ozone in the free troposphere include both increased ozone resulting from seasonal biomass burning in Africa and locally reduced ozone brought about by convective lifting of unpolluted boundary-layer air. Expanding to a 4×4 self-organizing map shows how biomass burning influences the yearly cycle of tropospheric ozone at Ascension Island and captures the seasonality of ozone at both Ascension Island and Natal. Comparing Ascension Island and Natal using a 4×4 self-organizing map at each site reveals similarities in mid-tropospheric ozone, but shows differences in lower-tropospheric ozone due to Ascension Island being closer to African biomass burning and more affected by descent from the mean Walker circulation, with less convective activity, than Natal.

Original languageEnglish (US)
Article numberD04302
JournalJournal of Geophysical Research Atmospheres
Volume117
Issue number4
DOIs
StatePublished - Jan 1 2012

Fingerprint

ozonesondes
Ascension
ozonesonde
Ozone
organizing
Self organizing maps
ozone
biomass burning
profiles
Biomass
biomass
Walker circulation
anthropogenic source
mixing ratio
Climate models
seasonality
Upper atmosphere
Troposphere
troposphere
climate modeling

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

Jensen, Anders A. ; Thompson, Anne Mee ; Schmidlin, F. J. / Classification of Ascension Island and Natal ozonesondes using self-organizing maps. In: Journal of Geophysical Research Atmospheres. 2012 ; Vol. 117, No. 4.
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Classification of Ascension Island and Natal ozonesondes using self-organizing maps. / Jensen, Anders A.; Thompson, Anne Mee; Schmidlin, F. J.

In: Journal of Geophysical Research Atmospheres, Vol. 117, No. 4, D04302, 01.01.2012.

Research output: Contribution to journalArticle

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