Decadal Influence of the Solar Cycle (DISC)

尽管由于温室气体水平的增加，预计全球气候将在下个世纪变暖，但未来十年左右的区域变化很可能由气候系统的非强迫自然变率主导。其中一些自然变率可能提前数月甚至数年就可预测，因为它们与相对缓慢的过程有关，特别是与海洋中的过程有关（El Niño，热盐环流的波动和海洋热含量的大尺度异常）。长期变率的另一个潜在来源来自众所周知的太阳输出的11年太阳变化，但信号如何到达地表的机制尚不清楚，因此，在用于十年预测的气候模型中不能很好地表示。在11年周期内，太阳总辐照度的百分比变化非常小，但紫外线的变化要大得多，这可能影响平流层温度和臭氧的产生。已经提出了各种机制来解释平流层太阳信号如何将其影响扩展到地表，包括通过大气环流变化的放大机制。观测分析表明，地表对太阳变率的响应是区域性的。关于在欧洲观测到的信号一直存在争议，但最近对欧洲长期观测记录的分析证实，在3-4年的滞后时间里存在一个强大的统计上显著的信号。包括哈德利中心HadGEM模式在内的气候模式能够捕捉到平流层上层对紫外线变化的响应，但不能再现平流层下层观测到的信号，也不能再现欧洲上空观测到的滞后信号。HadGEM模式对紫外线变化异常大的敏感性测试能够再现信号的滞后性质，因此显示出其再现信号的能力的一些希望，但地表响应幅度仍然太弱，这表明有显著改进的空间，这应该导致改进的十年预测。该提案的主要目的是改进hagedem气候模式中太阳对地球表面影响机制的表现，以便改进使用英国气象局DePreSys业务年代际预测模式进行的预测。该项目将采用HadGEM模型和一个更简单的模型进行广泛的机制测试，特别侧重于改进那些通过平流层加热异常将太阳信号传递到地表的机制的表示，以及涉及北大西洋大气-海洋耦合的地表放大机制。将通过比较选定年份的重新预报（预测）结果来检验HadGEM模型的改进，并特别注意大西洋/欧洲部分的改进。该项目将由牛津大学（Oxford University）和帝国理工学院（Imperial College）的研究人员执行。牛津大学将进行HadGEM调查，帝国理工学院将进行机械模型调查。英国气象局的项目合作伙伴将提供广泛的支持，他们将密切参与hagedem实验的解释和DePreSys预测系统改进的实施/测试，基尔大学的项目合作伙伴将对太阳光谱强迫提出建议，并在其他主要气候模式的背景下对结果进行解释。

Although global climate is expected to warm over the next century in response to increasing levels of greenhouse gases, regional changes over the next decade or so are likely to be dominated by unforced natural variability of the climate system. Some of this natural variability is potentially predictable months or even years in advance because it is related to relatively slow processes, especially those in the ocean (El Niño, fluctuations in the thermohaline circulation, and large-scale anomalies of ocean heat content). Another potential source of long-term variability comes from the well-known 11-year solar variations in the Sun's output but the mechanisms for how the signal reaches the surface is not well understood and, because of this, it is not well represented in climate models used for decadal predictions.The percentage variation in total solar irradiance over an 11-yr cycle is very small, but the variation in the UV is much larger and this can impact stratospheric temperatures and ozone production. Various mechanisms have been proposed to explain how this stratospheric solar signal may extend its influence to the surface, including amplifying mechanisms through atmospheric circulation changes. Analysis of observations show that the surface response to solar variability is regional. There has been controversy surrounding the observed signal over Europe, but recent analysis of long-term observational records over Europe have confirmed a strong statistically significant signal at lags of 3-4 years. Climate models, including the Hadley Centre HadGEM model, are able to capture an upper stratospheric response to changing UV, but do not reproduce the observed signal in the lower stratosphere nor the observed lagged signal over Europe.Sensitivity tests with the HadGEM model with an exceptionally large UV change was able to reproduce the lagged nature of the signal, thus showing some promise for its ability to reproduce the signal, but the surface response amplitude is still much too weak, suggesting that there is room for significant improvements which should lead to improved decadal forecasts. This prime aim of the proposal is to improve the representation of mechanisms of solar influence on the Earth's surface in the HadGEM climate model so that forecasts using the Met Office DePreSys operational decadal forecast model can be improved. The project will employ both the HadGEM model and a simpler model for extensive testing of mechanisms, with a particular focus on improving the representation of those mechanisms that transfer the solar signal to the surface via stratospheric heating anomalies and a surface amplifying mechanism that involves atmosphere-ocean coupling in the North Atlantic. The resulting improvements to the HadGEM model will be tested by comparing results from re-forecasts (hindcasts) of selected years, with particular attention to improvements in the Atlantic / European sector. The project will be performed by researchers at Oxford University who will carry out the HadGEM investigations and Imperial College who will perform the mechanistic model investigations. Extensive support will be provided by Project Partners at the Met Office, who will be closely involved in the interpretation of the HadGEM experiments and implementation / testing of improvements in the DePreSys forecast system and a Project Partner at Kiel University who will advise on solar spectral forcing and contribute to interpretation of results in the context of other major climate models.