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Multi-objective downscaling of precipitation time series by genetic programming
International Journal of Climatology ( IF 3.5 ) Pub Date : 2021-05-05 , DOI: 10.1002/joc.7172
Tanja Zerenner 1, 2 , Victor Venema 1 , Petra Friederichs 1 , Clemens Simmer 1
Affiliation  

We use symbolic regression to estimate daily precipitation amounts at six stations in the Alpine region from a global reanalysis. Symbolic regression only prescribes the set of mathematical expressions allowed in the regression model, but not its structure. The regression models are generated by genetic programming (GP) in analogy to biological evolution. The two conflicting objectives of a low root-mean-square error (RMSE) and consistency in the distribution between model and observations are treated as a multi-objective optimization problem. This allows us to derive a set of downscaling models that represents different achievable trade-offs between the two conflicting objectives, a so-called Pareto set. Our GP setup limits the size of the regression models and uses an analytical quotient instead of a standard or protected division operator. With this setup we obtain models that have a generalization performance comparable with generalized linear regression models (GLMs), which are used as a benchmark. We generate deterministic and stochastic downscaling models with GP. The deterministic downscaling models with low RMSE outperform the respective stochastic models. The stochastic models with low IQD, however, perform slightly better than the respective deterministic models for the majority of cases. No approach is uniquely superior. The stochastic models with optimal IQD provide useful distribution estimates that capture the stochastic uncertainty similar to or slightly better than the GLM-based downscaling.

中文翻译:

基于遗传规划的降水时间序列多目标降尺度

我们使用符号回归从全球再分析中估计阿尔卑斯地区六个站点的每日降水量。符号回归只规定了回归模型中允许的一组数学表达式,而不是它的结构。回归模型是通过类似于生物进化的遗传编程 (GP) 生成的。低均方根误差 (RMSE) 和模型与观测值之间分布的一致性这两个相互冲突的目标被视为多目标优化问题。这使我们能够推导出一组表示两个相互冲突的目标之间不同的可实现权衡的降尺度模型,即所谓的帕累托集。我们的 GP 设置限制了回归模型的大小,并使用分析商而不是标准或受保护的除法运算符。通过这种设置,我们获得了泛化性能与用作基准的广义线性回归模型 (GLM) 相当的模型。我们使用 GP 生成确定性和随机降尺度模型。具有低 RMSE 的确定性降尺度模型优于相应的随机模型。然而,在大多数情况下,具有低 IQD 的随机模型的性能略好于各自的确定性模型。没有一种方法是独一无二的。具有最佳 IQD 的随机模型提供了有用的分布估计,可以捕获与基于 GLM 的降尺度相似或稍好一些的随机不确定性。我们使用 GP 生成确定性和随机降尺度模型。具有低 RMSE 的确定性降尺度模型优于相应的随机模型。然而,在大多数情况下,具有低 IQD 的随机模型的性能略好于各自的确定性模型。没有一种方法是独一无二的。具有最佳 IQD 的随机模型提供了有用的分布估计,可以捕获与基于 GLM 的降尺度相似或稍好一些的随机不确定性。我们使用 GP 生成确定性和随机降尺度模型。具有低 RMSE 的确定性降尺度模型优于相应的随机模型。然而,在大多数情况下,具有低 IQD 的随机模型的性能略好于各自的确定性模型。没有一种方法是独一无二的。具有最佳 IQD 的随机模型提供了有用的分布估计,可以捕获与基于 GLM 的降尺度相似或稍好一些的随机不确定性。
更新日期:2021-05-05
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