RAPID: Drought Risk and Low-frequency Hydroclimatic Variability in CMIP5 Simulations

这是政府间气候变化专门委员会第五次评估报告（IPCC AR5）中鼓励对气候模式模拟进行诊断分析的致同事信（NSF 11-006）资助的16个快速响应（Rapid）项目之一。在这些项目中进行的研究预计将导致更详细的模式相互比较，更好地理解稳健模式行为，更好地理解和量化未来气候模拟中的不确定性。本项目考虑了为AR5准备的模式模拟在多大程度上能够再现仪器记录和古代用记录中发现的低频水文气候变率。在IPCC第四次评估报告（AR4）中使用的前一代模式被发现在捕捉低频水文气候变率方面存在缺陷，这一缺陷可能意味着这些模式的未来预测低估了包括美国西南部在内的地区长期干旱的风险。这里进行的研究旨在确定当前这一代模式是否产生更真实的低频水文气候变化。此外，还开发了从模式中重新调整干旱预估的方法，以产生对未来干旱风险的观测校正估计。该项目的更广泛影响在于它对IPCC第五次评估报告的支持，该报告旨在向全球决策者提供有关气候变化及其后果的信息。由于水文气候变率和变化对人类、农业和生态系统的巨大影响，它们具有重大的社会意义。这在北美西南部尤其如此，这是研究的重点地区。

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations.This project considers the extent to which model simulations prepared for AR5 are capable of reproducing the low-frequency hydroclimate variability found in the instrumented and paleo-proxy records. The earlier generation of models used in the IPCC Fourth Assessment Report (AR4) was found to be deficient in capturing low-frequency hydroclimate variability, and this deficiency could mean that future projections from the models underestimate the risk of prolonged drought in regions including the US southwest. Research conducted here seeks to determine if the current generation of models produces more realistic low-frequency hydroclimate variance. In addition, methods are developed to rescale drought projections from the models to produce observationally corrected estimates of future drought risk.The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. Hydroclimate variability and change are of great societal interest given their large impacts on people, agriculture, and ecosystems. This is particularly true in southwestern North America, a focus region for the research.