RAPID: Testing Storm Track Sensitivity to Resolution and Climate Change Using UPSCALE Global Model Output

世界上大部分地区的日常天气是由沿中纬度风暴路径移动的温带气旋驱动的。因此，准确的天气预报需要具有足够高分辨率的数值模式，以反映气旋及其演变的关键细节，而了解为此目的的足够分辨率是很重要的。同样需要足够的分辨率来进行模拟，以捕捉气旋和风暴路径对全球温度变化的反应，但目前尚不清楚什么是足够的分辨率。这是一个特别的问题，因为这种模拟的费用随着分辨率的增加而增加。pi先前的工作表明，高分辨率是必要的，以表示气旋内的小袋强降水，这些强降水促进了气旋的增强并产生了更强的气旋。此外，高分辨率模拟中的气旋在更温暖的条件下更为强烈，这是由于伴随比湿度随温度升高而上升的潜热增加。但是这些结果有些不确定，因为模拟是用区域模式进行的，因为缺乏获得足够分辨率的全球模式的机会。该项目利用高分辨率模拟解决了小尺度降水特征在气旋增强中的作用，以及在气候变暖中产生更强气旋的可能性。高分辨率模拟是英国高档项目的一部分（高档是英国在PRACE上的缩写，PRACE是欧洲高级计算伙伴关系）。高档项目以中、高分辨率（高达25公里）对当前气候条件和由于温室气体浓度增加而预计将出现的较暖气候进行了全球模拟。这些模拟非常适合pi的研究，尽管它们是出于其他原因而产生的。该项目通过RAPID机制资助，以加快研究，使其能够根据正在进行的英国项目的时间表进行。时间上的一个关键问题是，“高档”项目是更密集的PRIMAVERA项目的前身，后者将产生分辨率高达5公里的全球模拟。PRIMAVERA是欧洲对耦合模式比较项目第6版（CMIP6）的HighResMIP子项目的贡献，该子项目将为政府间气候变化专门委员会的下一份评估报告提供信息。因此，该项目的近期成果可以在确定PRIMAVERA的研究议程和为评估报告提供信息方面发挥关键作用。由于温带气旋对美国和其他中纬度地区的敏感天气的主要影响，以及对气候变化可能导致的气旋强度增加的指导价值，这项工作具有更广泛的影响。这项工作还建立了一个国际科学合作，使美国的pi能够获得高分辨率的模拟，成本很高。此外，该项目为研究生提供支持和培训，从而为该研究领域的下一代劳动力提供支持。

Day-to-day weather over much of the world is driven by extratropical cyclones traveling along the storm tracks of the middle latitudes. Accurate weather forecasts thus require numerical models with high enough resolution to represent critical details of the cyclones and their evolution, and it is important to understand what constitutes adequate resolution for this purpose. Adequate resolution is likewise required to produce simulations which capture the response of cyclones and storm tracks to changes in global temperature, but it is again unclear what constitutes adequate resolution. This is particularly an issue as the expense of such simulations increases strongly with resolution.Previous work by the PIs suggests that high resolution is necessary to represent small pockets of intense precipitation within the cyclones that promote cyclone intensification and produce more energetic cyclones. In addition, cyclones in the high resolution simulations are more intense under warmer conditions, due to the increase in latent heating that accompanies the rise in specific humidity with temperature. But these results are somewhat inconclusive as the simulations were performed with a regional model due to lack of access to global models with adequate resolution.This project addresses the role of small-scale precipitation features in the intensification of cyclones, and the resulting potential for more energetic cyclones in a warming climate, using high-resolution simulations carried out as part of the United Kingdom UPSCALE project (UPSCALE is short for UK on PRACE - weather-resolving Simulations of Climate for globAL Environmental risk, where PRACE is the Partnership for Advanced Computing in Europe). The UPSCALE project has produced global simulations at medium and high resolutions (up to 25km), both for present-day climate conditions and for warmer climates which are projected to occur due to increases in greenhouse gas concentrations. The simulations are ideally suited for the PIs' research although they were produced for other reasons.The project is funded through the RAPID mechanism to expedite the research so that it can be conducted according to the timeline of the ongoing UK project. A key issue in the timing is that UPSCALE is a precursor to the more intensive PRIMAVERA project, which will produce global simulations with resolutions as high as 5km. PRIMAVERA is the European contribution to the HighResMIP sub-project of the Coupled Model Intercomparison Project version 6 (CMIP6), which will inform the next assessment report of the Intergovernmental Panel on Climate Change. Near-term results of this project can thus play a critical role in defining the research agenda of PRIMAVERA and informing the assessment report.The work has broader impacts due to the dominant influence of extratropical cyclones on sensible weather over the US and other midlatitude regions, and the value of guidance regarding possible increases in cyclone intensity due to climate change. The work also builds an international scientific collaboration which allows US PIs access to high-resolution simulations produced at substantial cost. In addition, the project provides support and training for a graduate student, thereby providing for the next generation workforce in this research area.