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

dc.contributor.authorLandman, Willem Adolf
dc.contributor.authorDeWitt, David G.
dc.contributor.authorLee, Dong-Eun
dc.contributor.authorBeraki, Asmerom Fissehatsion
dc.contributor.authorLotter, Daleen
dc.date.accessioned2012-07-19T06:58:58Z
dc.date.available2012-07-19T06:58:58Z
dc.date.issued2012-04
dc.description.abstractForecast 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.librariannf2012en
dc.description.sponsorshipThe National Research Foundation (NRF) of South Africa and grants from the multiagency Climate Simulation Laboratory (CSL) program.en_US
dc.description.urihttp://www.ametsoc.org/pubs/journals/waf/index.htmlen_US
dc.identifier.citationLandman, 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.issn0882-8156 (print)
dc.identifier.issn1520-0434 (online)
dc.identifier.other10.1175/WAF-D-11-00078.1
dc.identifier.urihttp://hdl.handle.net/2263/19464
dc.language.isoenen_US
dc.publisherAmerican Meteorological Societyen_US
dc.rights© 2012 American Meteorological Societyen_US
dc.subjectSeasonal rainfallen
dc.subject.lcshRain and rainfall -- South Africa -- Forecastingen
dc.subject.lcshWeather forecasting -- Computer simulation -- South Africaen
dc.titleSeasonal rainfall prediction skill over South Africa : one- versus two-tiered forecasting systemsen
dc.typeArticleen

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