Flow dependent ensemble spread in seasonal forecasts of the boreal winter extratropics
Flow dependent ensemble spread in seasonal forecasts of the boreal winter extratropics
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北半球冬季温带地区季节性预报中的流量相关集合传播
DOI：
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发表时间：
2018
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影响因子：
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通讯作者：
A. Weisheimer
中科院分区：
文献类型：
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作者：
D. MacLeod;C. O’Reilly;T. Palmer;A. Weisheimer
流相关传播（FDS）是概率预报的一个理想特征;集合传播应该代表预期的预报误差。然而，这是很难估计的季节性后报，因为他们往往有一个相对较小的样本量。在这里，我们使用一个长（110年）的季节性后报数据集评估FDS在北方冬季北大西洋涛动（NAO）和太平洋北美模式（PNA）的预测。NAO和PNA的年际变化存在良好的FDS关系，负NAO和PNA事件存在轻度欠分散，正NAO存在轻度过分散。在预报误差中可以看到十年尺度的变化，但在集合传播中却没有，这表明在这个时间尺度上变化很小。还研究了预报误差与热带加热异常之间的联系，但没有发现强联系，但提出了东太平洋强厄尔尼诺变暖与PNA误差减少之间的弱联系。
Flow‐dependent spread (FDS) is a desirable characteristic of probabilistic forecasts; ensemble spread should represent the expected forecast error. However this is difficult to estimate for seasonal hindcasts as they tend to have a relatively small sample size. Here we use a long (110 year) seasonal hindcast dataset to evaluate FDS in forecasts of boreal winter North Atlantic Oscillation (NAO) and Pacific North American pattern (PNA). A good FDS relationship is found for interannual variations in both the NAO and PNA, with mild underdispersion for negative NAO and PNA events and slight overdispersion for positive NAO. Decadal‐scale variability is seen in forecast errors but not in ensemble spread, which shows little variation on this timescale. Links between forecast errors and tropical heating anomalies are also investigated, though no strong links are found. However, a weak link between strong El Niño warming in the East Pacific and reduced PNA error is suggested.