Origin and Impact of Initialization Shocks in Coupled Atmosphere-Ocean Forecasts*
Origin and Impact of Initialization Shocks in Coupled Atmosphere-Ocean Forecasts*
复制标题
大气-海洋耦合预报中初始化激波的起源和影响*
DOI：
10.1175/mwr-d-15-0076.1
复制
发表时间：
2015
影响因子：
3.2
通讯作者：
Mulholland D
中科院分区：
文献类型：
--
作者：
Mulholland D
目前初始化大气-海洋耦合预报的方法往往依赖于使用单独的大气和海洋分析，这两种分析的结合可能会使耦合系统在预报开始时不平衡，有可能加速产生误差。利用欧洲中期天气预报耦合系统的一系列试验，量化了这些所谓的初始化激波的强度和程度，并测量了它们对预报技能的影响。结果发现，与用耦合资料同化方法初始化的预报相比，单独的海洋和大气分析初始化的预报在较低的大气温度下确实表现出初始化激波。在一些地区，这些冲击导致预报第一天的均方根误差增加一倍之多，并在这里进行的10天预报期间持续增加。然而，使用独立数据集评估的这种初始化选择对预测技能的影响被发现是微不足道的，至少在研究的有限时期内是可以忽略的。在分析和预报阶段之间，发现大气或海洋模式分量的变化会产生更大的初始化激波：在预报的第一天，海洋分量的变化可导致一些赤道区域的海表面温度激波超过0.5K。讨论了发展耦合预报系统的意义，特别是关于耦合数据同化方法的含义。
Current methods for initializing coupled atmosphere–ocean forecasts often rely on the use of separate atmosphere and ocean analyses, the combination of which can leave the coupled system imbalanced at the beginning of the forecast, potentially accelerating the development of errors. Using a series of experiments with the European Centre for Medium-Range Weather Forecasts coupled system, the magnitude and extent of these so-called initialization shocks is quantified, and their impact on forecast skill measured. It is found that forecasts initialized by separate oceanic and atmospheric analyses do exhibit initialization shocks in lower atmospheric temperature, when compared to forecasts initialized using a coupled data assimilation method. These shocks result in as much as a doubling of root-mean-square error on the first day of the forecast in some regions, and in increases that are sustained for the duration of the 10-day forecasts performed here. However, the impacts of this choice of initialization on forecast skill, assessed using independent datasets, were found to be negligible, at least over the limited period studied. Larger initialization shocks are found to follow a change in either the atmosphere or ocean model component between the analysis and forecast phases: changes in the ocean component can lead to sea surface temperature shocks of more than 0.5 K in some equatorial regions during the first day of the forecast. Implications for the development of coupled forecast systems, particularly with respect to coupled data assimilation methods, are discussed.