Assessing the Impact of Parameterized Gravity Wave Drag on Climate Change Forecasts: A Systematic Investigation with Global Circulation Models

该项目旨在了解和量化气候模型中与重力波阻力(GWD)参数相关的不确定性，特别是气候变化预测。重力波通过在对流层和平流层之间和内部传输动量来影响全球大气环流，但由于重力波太小，无法在最先进的气候模型中充分解决。因此，它们的影响是基于模型的解析变量来估计或参数化的。最近的研究表明，全球变暖参数的不确定性对对流层和平流层对人为强迫的响应都有一阶影响。现有的参数化研究大多是在固定背景风的情况下“离线”进行的，不足以量化这些不确定性，因为全球变暖的影响因与天气和行星波的相互作用而被放大。为了解决这些问题，研究人员将建立一个框架，用于在理想化的大气环流模式(GCM)中测试GWD参数。理想化的GCM捕捉到的平流层和对流层环流非常逼真，但具有计算效率，使我们能够系统地评估GWD参数对气候变化的影响，这是由对流层(即热带高层对流层变暖)和平流层(即与臭氧损失/恢复相关的极涡的冷却/加热)的趋势所驱动的。研究人员将使用该模式来了解全球变暖对(1)对流层环流的趋势，特别是热带外急流的变化，(2)平流层环流的趋势，特别是布鲁尔-多布森环流的趋势，以及(3)平流层的气候和可变性的影响。研究的更广泛的影响是(1)帮助提高对气候变化预测的理解和信心，(2)教育和指导本科生和研究生水平的学生，以及(3)提供对气候预测的更一般的理解。气候预测固有的不确定性是科学界与公众沟通的一个重大问题。这个项目提供了一个案例研究，说明如何使用模型(特别是GCM)来量化不确定性，并将其用于针对本科生的推广。

This project seeks to understand and quantify the uncertainty associated with gravity wave drag (GWD) parameterization in climate models, particularly for climate change forecasts. Gravity waves influence the global circulation of the atmosphere by transporting momentum between and within the troposphere and stratosphere, but are too small to be adequately resolved in state-of-the-art climate models. Hence their effects are estimated, or parameterized, based on the resolved variables of the model. Recent studies have demonstrated that uncertainty in how GWD is parameterized has a first order impact on both the tropospheric and stratospheric response to anthropogenic forcing. Existing studies of parameterizations, largely performed "offline" with fixed background winds, are insufficient to quantify these uncertainties, as the impact of GWD is amplified by interaction with synoptic and planetary waves. To redress these concerns, the investigators will establish a framework for testing GWD parameterizations in an idealized general circulation model (GCM).The idealized GCM captures the stratospheric and tropospheric circulation with fidelity, but with computational efficiency that permits us to systematically assess the impact of GWD parameters on a changing climate, driven both by trends in the troposphere (i.e. tropical upper tropospheric warming) and stratosphere (i.e. the cooling/heating of the polar vortex associated with ozone loss/recovery). The investigators will use the model to understand the influence of GWD on (1) trends in the tropospheric circulation, in particular shifts in the extratropical jet streams, (2) trends in the stratospheric circulation, in particular the Brewer-Dobson Circulation, and (3) stratospheric climate and variability.The broader impacts of the research are (1) to help improve understanding and confidence in climate change forecasts, (2) to educate and mentor students at the undergraduate and graduate level, and (3) to provide a more general understanding of climate forecasting. The inherent uncertainty in climate prediction is a significant problem for the scientific community in communicating with the public. This project provides a case study in how models (in particular GCMs) can be used to quantify uncertainty, and used for outreach directed at undergraduate students.