Impact of lower stratospheric ozone on seasonal prediction systems

• Published in: South African Journal of Science Vol. 110; no. 3-4; p. 1
• Main Authors: Mathole, Kelebogile, Ndarana, Thando, Beraki, Asmerom, Landman, Willem A
• Format: Journal Article
• Language: English
• Published: Pretoria African Online Scientific Information Systems (Pty) Ltd t/a AOSIS 01.03.2014; Academy of Science of South Africa
• Subjects: Atmospheric circulation; Boundary conditions; Climate; Climate models; Cooling; eddy-driven jet; El Nino; ENSO; Environmental aspects; General circulation models; Greenhouse gases; Ocean currents; Ozone; ozone depletion; polar vortex; Rain; Stratosphere; Summer; Trends; South Africa; Africa
• DOI: 10.1590/sajs.2014/20130161
• ISSN: 0038-2353

The authors have conducted a comparison of trends in lower stratospheric temperatures and summer zonal wind fields based on 27 years of reanalysis data and output from hindcast simulations using a coupled ocean-atmospheric general circulation model (OAGCM). Lower stratospheric ozone in the OAGCM was relaxed to the observed climatology and increasing greenhouse gas concentrations were neglected. In the reanalysis, lower stratospheric ozone fields were better represented than in the OAGCM. The spring lower stratospheric/ upper tropospheric cooling in the polar cap observed in the reanalysis, which is caused by a direct ozone depletion in the past two decades and is in agreement with previous studies, did not appear in the OAGCM. The corresponding summer tropospheric response also differed between data sets. In the reanalysis, a statistically significant poleward trend of the summer jet position was found, whereas no such trend was found in the OAGCM. Furthermore, the jet position in the reanalysis exhibited larger interannual variability than that in the OAGCM.