SGER: El Nino-Southern Oscillation (ENSO) and Droughts over North America--The Interdecadal Variability of the Sea Surface Temperature (SST) Forced Signal

SGER：厄尔尼诺-南方涛动（ENSO）和北美干旱——海面温度（SST）强迫信号的年代际变化

• 批准号: 0739323
• 负责人: Annalisa Bracco
• 金额: $ 2.84万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0739323&HistoricalAwards=false
• 关键词: SGER; El; Nino; Southern; Oscillation

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.Theory, results from atmospheric general circulation models (AGCMs), and observational and proxy data support the hypothesis that changes in the frequency and amplitude of interannual variability in the tropics can modulate the occurrence and duration of droughts over North America. Various mechanisms for the atmospheric teleconnection between the tropical Pacific and North America have been hypothesized to explain the tendency for droughts to occur in the presence of cool sea surface temperature (SST) anomalies, i.e., in La Nina-like conditions. Analyses of instrumental records from the most recent decades, however, reveal that our understanding of these interactions is incomplete.This project is an exploratory investigation, using newly available model output, of the possible role played by the tropical Pacific during the second half of the 20th century and in future warmer climates in modulating the occurrence and duration of droughts in North America. The investigators will attempt to answer the following questions:. Which part of the circulation anomalies that create droughts over North America results from tropical SST forcing (ENSO, El Nino-Southern Oscillation, in particular) and which part results from internal modes of the atmosphere?. Would changes in the ENSO characteristics - variance and mean state in particular - affect the probability of drought occurrence and/or drought duration and extent in the United States?The first question will be addressed by means of exploratory analyses of a large number of simulations collected as part of the Climate of the 20th Century (C20C) international project. The potential predictability of North American observed rainfall will be assessed by systematically comparing the output of different AGCMs during the period 1950-1999 and separately during the 1950-1976 and 1977-1999 intervals. This may allow the significance of changes in the atmospheric patterns associated with North American precipitation before and after the 1976 climate shift in the Pacific to be assessed. To investigate the second point the principal investigator will analyze a suite of IPCC AR4 (Intergovernmental Panel on Climate Change Fourth Assessment Report) coupled runs to test the role of ENSO variance, direction of propagation of SST anomalies, and persistence of SST and wind anomalies as well as the role of the general warming in the tropics in modulating the occurrence and duration of droughts over North America.Broader impacts of the work lie in its potential for assessing how the risk of North American drought will evolve over this century.

这是气候变率和可预测性 (CLIVAR) 计划试点项目 DRICOMP 下的一笔赠款，用于耦合模型干旱项目，该项目的重点是对干旱机制进行初步探索，因为它们在全球气候模型的输出中有所体现，并试图评估这些模型在模拟干旱方面的可靠性。理论、大气环流模型 (AGCM) 的结果以及观测和代理数据支持 假设热带地区年际变化的频率和幅度的变化可以调节北美干旱的发生和持续时间。 人们已经假设了热带太平洋和北美之间大气遥相关的各种机制，以解释在冷海面温度（SST）异常（即在类似拉尼娜的条件下）出现干旱的趋势。 然而，对最近几十年仪器记录的分析表明，我们对这些相互作用的理解并不完整。该项目是一项探索性调查，利用新获得的模型输出，探讨热带太平洋在 20 世纪下半叶以及未来气候变暖在调节北美干旱的发生和持续时间方面可能发挥的作用。 调查人员将尝试回答以下问题：造成北美干旱的环流异常的哪一部分是由热带海温强迫（特别是ENSO、厄尔尼诺-南方涛动）造成的，哪一部分是由大气内部模式造成的？ ENSO 特征的变化（尤其是方差和平均状态）是否会影响美国发生干旱的概率和/或干旱持续时间和程度？第一个问题将通过对作为 20 世纪气候 (C20C) 国际项目一部分收集的大量模拟数据进行探索性分析来解决。 将通过系统地比较 1950-1999 年期间以及分别在 1950-1976 年和 1977-1999 年期间不同 AGCM 的输出来评估北美观测到的降雨量的潜在可预测性。 这可能有助于评估 1976 年太平洋气候变化前后与北美降水相关的大气模式变化的重要性。 为了研究第二点，首席研究员将分析一套IPCC AR4（政府间气候变化专门委员会第四次评估报告）耦合运行，以测试ENSO方差的作用、海温异常的传播方向、海温和风异常的持续性以及热带地区普遍变暖在调节北方干旱发生和持续时间方面的作用 美国。这项工作的更广泛影响在于其评估本世纪北美干旱风险将如何演变的潜力。