Direct and indirect seasonal rainfall forecasts for East Africa using global dynamical models
Direct and indirect seasonal rainfall forecasts for East Africa using global dynamical models
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使用全球动态模型对东非进行直接和间接季节性降雨预测
DOI：
10.1002/joc.6260
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Colman A
中科院分区：
文献类型：
--
作者：
Colman A
区域尺度的季节气候展望通常是使用该地区当地或与该地区遥相关的另一个地区的预测信息来制作的。动态的全球长期预报（LRF）系统可以提供这两种类型的信息，这两种方法进行了比较的情况下，在两个相邻地区的季节性降雨预报在热带东非的非洲之角地区。直接方法利用该区域的未处理LRF输出。对于“间接”方法，典型相关分析被使用，并通过识别与东非地区观测到的变率相关的大型热带区域的历史LRF预测模式来工作。对于给定的一年，LRF预测到这些模式的预测，然后可以用来构建区域预测。这种方法利用了LRF系统在大尺度变异性方面比在较小区域尺度特征方面具有更高技能的趋势。使用案例研究，发现这两种方法包含互补的信息：间接方法可以提供显着的技术优势，在强大尺度强迫的年份，而在某些年份，特别是当大尺度信号很弱，“直接”预测是优越的上级。多年来的技能比较发现，尽管结果取决于地区/季节，但一般来说，间接方法具有更高的整体技能，其改进等于或大于直接方法缩短1个月的交货时间所提供的改进。使用目前运行的动态LRF系统的数据，提供了这两个地区3月至4月至5月和9月至12月季节单独使用和组合使用的两种方法的结果。技能是最好的9月至12月的季节在南部地区，使用“间接”预测。对于北方地区的3月至5月季节，“直接”方法优于“间接”方法。总的来说，合并并没有产生实质性的好处。
Regional‐scale seasonal climate outlooks are typically produced using forecast information either local to the region or from another area with teleconnections to the region. Dynamical global long‐range forecast (LRF) systems can provide both types of information, and these two approaches are compared in the context of seasonal rainfall forecasts for two adjoining areas in the Greater Horn of Africa region in tropical East Africa. The direct method utilizes the unprocessed LRF outputs for the region. For the “indirect” method, canonical correlation analysis is used and works by identifying patterns in historical LRF predictions over large tropical domains that relate to observed variability in the East Africa regions. For a given year, projections of the LRF forecasts onto those patterns can then be employed to construct the regional forecasts. This approach takes advantage of the tendency for LRF systems to have greater skill for large‐scale variability than for smaller regional‐scale features. Using case studies, it is found the two approaches contain complementary information: the indirect approach can provide notable skill benefits in years with strong large‐scale forcing while in some years, particularly when large‐scale signals are weak, the “direct” forecast are superior. Skill comparisons over many years found that, although results are region/season dependent, in general the indirect approach has higher skill overall—with improvements equal to or greater than those afforded by a 1‐month reduction in lead time with the direct approach. Results for both methods used separately and in combination are provided for the March–April–May and September‐to‐December seasons in the two regions, using data from currently operational dynamical LRF systems. Skill was best for the September‐to‐December season in the southern region, using “indirect” forecasts. The “direct” approach was better than “indirect” for the March‐to‐May season in the northern region. In general, combination did not produce a substantial benefit.
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DOI：
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发表时间：
2011
期刊：
影响因子：
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作者：
R. Graham;W. Yun;J. Kim;A. Kumar;D. Jones;L. Bettio;N. Gagnon;Rk Kolli;D. Smith
通讯作者：
D. Smith
ECMWF 的新型长期预报系统 SEAS 5
DOI：
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发表时间：
2018
期刊：
影响因子：
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作者：
T. Stockdale;Stephanie J. Johnson;L. Ferranti;M. Balmaseda;Simona Briceag
通讯作者：
Simona Briceag
DOI：
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发表时间：
1989
期刊：
影响因子：
--
作者：
K. Fraedrich;Neville R. Smith
通讯作者：
Neville R. Smith
影响因子：
4.6
作者：
Dean P. Walker;C. Birch;J. Marsham;Adam A. Scaife;Richard J. Graham;Z. Segele
通讯作者：
Dean P. Walker;C. Birch;J. Marsham;Adam A. Scaife;Richard J. Graham;Z. Segele