The response of numerical weather prediction systems to fgge level iib data. Part II: Forecast verifications and implications for predictability
The response of numerical weather prediction systems to fgge level iib data. Part II: Forecast verifications and implications for predictability
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数值天气预报系统对 fgge 级 iib 数据的响应。
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
P. Kållberg
中科院分区：
文献类型：
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作者：
K. Arpe;A. Hollingsworth;M. S. Tracton;A. Lorenc;S. Uppala;P. Kållberg
我们的两部分研究的目的是评估相同FGGE IIb级观察数据集的三个独立分析之间差异的重要性。第一部分是关于分析之间的差异的性质和根源。研究的第二部分关注的是预测技能的分析差异的影响，并为可预测性的估计。
我们的实验材料是一组预测的两个模型从三个合奏的分析。分析的能量学是不同的，这反映在基于分析的预测的能量学的差异上。
客观预报检验结果表明，两种模型的预报技巧有明显差异。这些核查还表明，对初始数据的选择具有明显的敏感性。
我们比较详细地研究了用同一模型从不同的分析中得出的预测是如何相互偏离的，特别关注三个方面：（1）小幅度的增长率;（2）差异达到渐近水平所需的时间;（3）这个水平相对于持续性的幅度。小振幅增长率的结果与早期的结果一致，即在第1-2天的预报中高度场的倍增时间为2.0天，但风场的增长率较慢（倍增时间为2.6天）。斜压波增长较快，倍增时间缩短约0.25天。预测的差异达到渐近水平更快，在这比在早期的调查。这表明，早期对瞬时天气模式可预测性的纯动力潜力的估计可能过于乐观。
我们结合了预测技能和预测分歧的措施，在一个误差预算，分离的贡献，预测误差所产生的模型误差和分析误差，受到一些简化的假设。结果表明，在第2天和第5天之间，模型误差随时间线性增长，而分析误差呈指数增长。该模式是这段时间内预测误差的主要来源。分析误差是短期天气预报误差的主要来源，在大约第五天之后，分析误差是一个重要因素。这些结果对初始分析误差的大小非常敏感。
这些统计结果与第一部分的天气学结果一起，强调了分析技术对预报成功的重要性，特别是在中期。在相同的高质量数据下，三个先进的分析系统产生的分析导致了相当不同的预测。
这些结果是基于2.5天的小样本，基本上代表相同的天气情况;因此，结果的一般性应在进一步的实验中进行测试。
The purpose of our two-part study is to assess the importance of the differences between three independent analyses of the same FGGE level IIb observational dataset. Part I is concerned with the nature and origin of the differences among the analyses. Part II of the study is concerned with the implications of the analysis differences for forecast skill, and for estimates of predictability.
Our experimental material is a set of forecasts by two models from the three ensembles of analyses. the energetics of the analyses are different, and this is reflected in differences in the energetics of the forecasts based on the analyses.
A study of the objective forecast verifications shows that there are clear differences in the forecast skill of the two models we used. the verifications also show a marked sensitivity to the choice of initial data.
We studied in some detail how forecasts made with the same model from different analyses diverge from one another, with particular attention to three aspects: (i) the growth rate at small amplitude; (ii) the time taken for the differences to reach an asymptotic level; (iii) the amplitude of this level relative to that of persistence. the results for small amplitude growth rates are consistent with earlier results in giving a doubling time of 2·0 days in the height field in the day 1-2 forecasts but with slower growth rates (doubling times of 2·6 days) in the wind field. the baroclinic waves show faster growth, with about 0·25 days shorter doubling times. the forecast differences reach an asymptotic level more rapidly in this than in earlier investigations. This suggests that earlier estimates of the purely dynamical potential for predictability of instantaneous weather patterns may be overoptimistic.
We combined the measures of forecast skill and forecast divergence in an error budget which separated the contributions to forecast error arising from model error and analysis error, subject to some simplifying assumptions. the results show that between day 2 and day 5 the model error grows linearly in time and the analysis error grows exponentially. the model is the main source of forecast error in this time range. the analysis error is the main source of forecast error in the short-range forecasts, and is a substantial contributor after about day 5. These results are very sensitive to the magnitude of the initial analysis errors.
Taken together with the synoptic results of part I, these statistical results emphasize the importance of analysis technique for the success of forecasting, particularly in the medium range. Given identical data of good quality, three advanced analysis systems produced analyses which lead to rather different forecasts.
The results are based on a small sample over a period of 21/2 days, which represent essentially the same synoptic situation; therefore the generality of the results should be tested on further experiments.