Ensemble forecasts of a flood-producing storm: comparison of the influence of model-state perturbations and parameter modifications
Ensemble forecasts of a flood-producing storm: comparison of the influence of model-state perturbations and parameter modifications
复制标题
洪水风暴的集合预报：模型状态扰动和参数修改的影响比较
DOI：
10.1002/qj.1951
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发表时间：
2012
影响因子：
8.9
通讯作者：
Leoncini G
中科院分区：
文献类型：
--
作者：
Leoncini G
高分辨率集合模拟（Δx= 1 km）是使用英国气象局统一模型对2004年8月16日的Boscastle（康沃尔，英国）山洪事件进行的。通过比较两种扰动策略的模拟结果，分析了由于预报模型的不完善而引起的预报不确定性。受事件的气象学影响，一种扰动会改变模型参数化方案中的相关物理选择或参数设置。另一种类型的扰动被设计用于解释边界层参数化中的代表性误差。它直接改变模型状态，并提供一个下限，以判断其他不确定性产生的传播。Boscastle在大约60公里的范围内拥有真正的技能，并且只有8名成员的合奏传播可以估计在10%以内。讨论了模型状态扰动和物理修改策略之间的差异，前者对触发更重要，后者对随后的单元发展更重要，包括对流单元的平均内部结构。尽管存在这些差异，但在熟练尺度下评估的降雨传播对扰动策略仅弱敏感。这表明，处理模式不确定性的相对简单的策略可能足以用于实际的对流尺度集合预报。版权所有© 2012皇家气象学会和英国皇家气象局版权所有
High‐resolution ensemble simulations (Δx= 1 km) are performed with the Met Office Unified Model for the Boscastle (Cornwall, UK) flash‐flooding event of 16 August 2004. Forecast uncertainties arising from imperfections in the forecast model are analysed by comparing the simulation results produced by two types of perturbation strategy. Motivated by the meteorology of the event, one type of perturbation alters relevant physics choices or parameter settings in the model's parametrization schemes. The other type of perturbation is designed to account for representativity error in the boundary‐layer parametrization. It makes direct changes to the model state and provides a lower bound against which to judge the spread produced by other uncertainties. The Boscastle has genuine skill at scales of approximately 60 km and an ensemble spread which can be estimated to within ∼ 10% with only eight members. Differences between the model‐state perturbation and physics modification strategies are discussed, the former being more important for triggering and the latter for subsequent cell development, including the average internal structure of convective cells.Despite such differences, the spread in rainfall evaluated at skilful scales is shown to be only weakly sensitive to the perturbation strategy. This suggests that relatively simple strategies for treating model uncertainty may be sufficient for practical, convective‐scale ensemble forecasting. Copyright © 2012 Royal Meteorological Society and British Crown Copyright, the Met Office