| DOI: | 10.1007/s00382-012-1520-z
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| Scopus记录号: | 2-s2.0-84878109151
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| 论文题名: | Seasonal forecasts for regional onset of the West African monsoon |
| 作者: | Vellinga M.; Arribas A.; Graham R.
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| 刊名: | Climate Dynamics
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| ISSN: | 9307575
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| 出版年: | 2013
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| 卷: | 40, 期:2017-11-12 | | 起始页码: | 3047
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| 结束页码: | 3070
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| 语种: | 英语
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| 英文关键词: | Onset
; Seasonal forecasts
; West African monsoon
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| 英文摘要: | The West African monsoon has over the years proven difficult to represent in global coupled models. The current operational seasonal forecasting system of the UK Met Office (GloSea4) has a good representation of monsoon rainfall over West Africa. It reproduces the various stages of the monsoon: a coastal phase in May and June, followed by onset of the Sahelian phase in July when rainfall maxima shift northward of 10N until September; and a secondary coastal rainfall maximum in October. We explore the dynamics of monsoon onset in GloSea4 and compare it to reanalyses. An important difference is the change in the Saharan heat low around the time of Sahelian onset. In Glosea4 the deepening heat low introduces moisture convergence across an east-west Sahelian band, whereas in the reanalyses such an east-west organisation of moisture does not occur and moisture is transported northwards to the Sahara. Lack of observations in the southern Sahara makes it difficult to verify this process in GloSea4 and also suggests that reanalyses may not be strongly constrained by station observations in an area key to Sahelian onset. Timing of monsoon onset has socio-economic importance for many countries in West Africa and we explore onset predictability in GloSea4. We use tercile categories to calculate probabilities for onset occurring before, near and after average in four different onset indicators. Glosea4 has modest skill at 2-3 months' lead time, with ROC scores of 0.6-0.8. Similar skill is seen in hindcasts with models from the ENSEMBLES project, even in models with large rainfall biases over the Sahel. Forecast skill derives from tropical SST in June and many models capture at least the influence of the tropical Atlantic. This suggests that long-range skill for onset could be present in other seasonal forecasting systems in spite of mean rainfall biases. © 2012 Crown Copyright. |
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| 资源类型: | 期刊论文
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/54899
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| Appears in Collections: | 过去全球变化的重建
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作者单位: | Met Office Hadley Center, FitzRoy Road, Exeter, EX1 3PB, United Kingdom
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| Recommended Citation: | |
Vellinga M.,Arribas A.,Graham R.. Seasonal forecasts for regional onset of the West African monsoon[J]. Climate Dynamics,2013-01-01,40(2017-11-12)
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