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

世界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推动的。因此，准确的天气预报需要具有足够高分辨率的数值模式，以表示气旋及其演变的关键细节，重要的是了解为此目的什么构成了适当的分辨率。同样需要足够的分辨率来产生模拟，捕捉气旋和风暴路径对全球气温变化的反应，但仍然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急剧增加。PI先前的工作表明，高分辨率对于表示气旋内的小块强降水是必要的，这些小块强降水促进了气旋的加强并产生了更高能量的气旋。此外，高分辨率模拟中的气旋在较温暖的条件下更加强烈，这是因为潜热增加伴随着比湿度随温度的上升而增加。但这些结果有些不确定，因为由于无法获得足够分辨率的全球模式，模拟是用区域模式进行的。该项目使用作为联合王国高级项目(UpScale是英国在PRACE-天气解析气候模拟全球环境风险方面的简写，其中PRACE是欧洲高级计算伙伴关系)进行的高分辨率模拟，研究了小尺度降水特征在气旋增强中的作用，以及由此产生的在变暖的气候中更具能量的气旋的可能性。这一高级项目制作了中分辨率和高分辨率(高达25公里)的全球模拟，既针对目前的气候条件，也针对预计将因温室气体浓度增加而发生的气候变暖。这些模拟非常适合PIS的研究，尽管它们是出于其他原因而产生的。该项目通过快速机制提供资金，以加快研究，以便可以根据正在进行的英国项目的时间表进行。时机上的一个关键问题是，高端项目是更密集的Primavera项目的先驱，该项目将产生分辨率高达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分项目的贡献，它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，该项目的近期结果可以在确定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具有主导影响，以及气候变化可能导致气旋强度增加的指导价值，该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，允许美国PI访问以相当大的成本产生的高分辨率模拟。此外，该项目还为研究生提供支持和培训，从而为这一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.