Seasonal rainfall prediction skill over South Africa : one- versus two-tiered forecasting systems

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dc.contributor.author Landman, W.A. (Willem Adolf), 1964-
dc.contributor.author DeWitt, David G.
dc.contributor.author Lee, Dong-Eun
dc.contributor.author Beraki, Asmerom Fissehatsion
dc.contributor.author Lotter, Daleen
dc.date.accessioned 2012-07-19T06:58:58Z
dc.date.available 2012-07-19T06:58:58Z
dc.date.issued 2012-04
dc.description.abstract Forecast performance by coupled ocean–atmosphere or one-tiered models predicting seasonal rainfall totals over South Africa is compared with forecasts produced by computationally less demanding two-tiered systems where prescribed sea surface temperature (SST) anomalies are used to force the atmospheric general circulation model. Two coupled models and one two-tiered model are considered here, and they are, respectively, the ECHAM4.5–version 3 of the Modular Ocean Model (MOM3-DC2), the ECHAM4.5-GML–NCEP Coupled Forecast System (CFSSST), and the ECHAM4.5 atmospheric model that is forced with SST anomalies predicted by a statistical model. The 850-hPa geopotential height fields of the three models are statistically downscaled to SouthAfrican Weather Service district rainfall data by retroactively predicting 3-month seasonal rainfall totals over the 14-yr period from1995/96 to 2008/09.Retroactive forecasts are produced for lead times of up to 4 months, and probabilistic forecast performance is evaluated for three categories with the outer two categories, respectively, defined by the 25th and 75th percentile values of the climatological record. The resulting forecast skill levels are also compared with skill levels obtained by downscaling forecasts produced by forcing the atmospheric model with simultaneously observed SST in order to produce a reference forecast set. Downscaled forecasts from the coupled systems generally outperform the downscaled forecasts from the twotiered system, but neither of the two systems outscores the reference forecasts, suggesting that further improvement in operational seasonal rainfall forecast skill for South Africa is still achievable. en
dc.description.librarian nf2012 en
dc.description.sponsorship The National Research Foundation (NRF) of South Africa and grants from the multiagency Climate Simulation Laboratory (CSL) program. en_US
dc.description.uri http://www.ametsoc.org/pubs/journals/waf/index.html en_US
dc.identifier.citation Landman, WA, DeWitt, D, Lee, D-E, Beraki, A & Lotter, D 2012, 'Seasonal rainfall prediction skill over South Africa : one- versus two-tiered forecasting systems', Weather and Forecasting, vol. 27, pp. 489-501. en
dc.identifier.issn 0882-8156 (print)
dc.identifier.issn 1520-0434 (online)
dc.identifier.other 10.1175/WAF-D-11-00078.1
dc.identifier.uri http://hdl.handle.net/2263/19464
dc.language.iso en en_US
dc.publisher American Meteorological Society en_US
dc.rights © 2012 American Meteorological Society en_US
dc.subject Seasonal rainfall en
dc.subject.lcsh Rain and rainfall -- South Africa -- Forecasting en
dc.subject.lcsh Weather forecasting -- Computer simulation -- South Africa en
dc.title Seasonal rainfall prediction skill over South Africa : one- versus two-tiered forecasting systems en
dc.type Article en


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