SGER: Diagnosing El Nino-induced Tropical Droughts in Seasonal Forecasts and Climate Change Projections

这是气候变异性和可预测性(CLIVAR)计划试点项目DRICOMP下的一项拨款，用于耦合模式干旱项目，该项目专注于对干旱机制进行初步探索，因为它们代表了全球气候模式的输出，并试图评估这些模型在模拟干旱方面的可靠性。厄尔尼诺现象给热带地区带来了广泛的干旱，包括墨西哥和南美洲北部。未来更强或更频繁的厄尔尼诺现象将加剧这些高度脆弱地区的干旱风险。即使厄尔尼诺事件的频率和强度在21世纪不会增加，热带太平洋更加普遍的变暖仍可能产生类似于今天厄尔尼诺条件的热带遥相关。业务季节性预报能否捕捉到导致热带干旱的条件，这是一个完全悬而未决的问题。这项研究是对厄尔尼诺引起的热带干旱的模式、空间范围和严重程度的初步探索，在20世纪的一个控制期内，季节预报更新了现实的初始条件但固定了温室气体(GHGs)，气候变化预测更新了现实的温室气体演变，但没有观测更新。然后，将对21世纪热带干旱模式的强度预测变化进行审查。这项研究将试图解决以下问题：耦合模型在模拟20世纪与厄尔尼诺相关的热带干旱的模式和强度方面有多好？在20世纪，季节预测模型和气候变化模型在厄尔尼诺变化和变化方面的主要区别是什么？年际降水变化模式在多大程度上影响21世纪的降水趋势，其余趋势的空间特征是什么？该项目的更广泛影响是评估热带干旱频率和严重程度变化的全球气候模型预测的可信度。它还可能为“重新校准”全球气候模型的输出提供基础，从而提高它们预测热带降雨变化的可靠性。该项目将支持巴西气象局气候研究中心(CPTEC)的科学家Caio A.S.Coelho访问美国，与首席调查员合作。这将有助于CPTEC与哥伦比亚大学国际气候与社会研究所(IRI)之间的持续合作。

This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought.El Nino brings widespread drought to the tropics, including Mexico and northern South America. Stronger or more frequent El Nino events in the future will exacerbate drought risk in these highly vulnerable areas. Even if the frequency and intensity of El Nino events do not increase in the 21st century, more generalized warming of the tropical Pacific may still produce a tropical teleconnection resembling that associated with present-day El Nino conditions. Whether or not operational seasonal forecasts can capture the conditions that cause tropical drought is an entirely open question. This study is an initial exploration of the patterns, spatial extent, and severity of El Nino induced tropical droughts during a control period in the 20th century in seasonal forecasts, which have updated realistic initial conditions but fixed greenhouse gases (GHGs), and in climate change projections, which have realistic GHG evolution but no observational updates. The projected changes in the strength of the identified patterns of tropical drought will then be examined for the 21st century runs. This research will attempt to address the following questions:. How well do coupled models simulate the pattern and intensity of tropical droughts associated with El Nino during the 20th century?. What are the primary differences of El Nino variability and change between seasonal prediction models and climate change models in the 20th century?. To what extent do patterns of interannual precipitation variability project on 21st century precipitation trends, and what is the spatial signature of the remaining trends?Broader impacts of this project are in assessing the credibility of global climate model projections of changes in the frequency and severity of tropical droughts. It may also provide a basis for "recalibrating" the output of global climate models, so as to improve their reliability in projecting changes in tropical rainfall. The project will support the visit of Caio A. S. Coelho, a scientist at the Centro de Previsao de Tempo e Estudos Climaticos (CPTEC), an institute of the Brazilian Meteorological Service, to the United States to collaborate with the principal investigator. This will contribute to an ongoing collaboration between CPTEC and the International Research Institute for Climate and Society (IRI) at Columbia University.