Dynamical Diagnoses of the Observed 'Asian Summer-Monsoon Rainfall - El Nino' Relationship

观测到的“亚洲夏季-季风降雨-厄尔尼诺”关系的动力学诊断

• 批准号: 9316278
• 负责人: Sumant Nigam
• 金额: $ 29.3万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-03-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9316278&HistoricalAwards=false
• 关键词: Dynamical; Diagnoses; Observed; Asian; Summer

Abstract ATM-9316278 Nigam, Sumant University of Maryland - College Park Title: Dynamical Diagnoses of the Observed 'Asian Summer-Monsoon Rainfall - El Nino' Relationship The project seeks to establish the dynamical basis for an empirical linkage between interannual fluctuations in the Asian summer- monsoon rainfall and the El Nino/La Nina episodes through diagnostic modeling of the observed monthly/ seasonal tropospheric circulation anomalies over the Asian continent (and global tropics and extratropics) during both the northern summer and the pre-'monsoon-onset' (March-May) seasons. An understanding of the forcing of the lower-tropospheric and near-surface circulation anomalies will be emphasized as these are critical both to the generation of monsoon-rainfall anomalies and tropical oceanic- circulation anomalies. The project objectives also include diagnostic modeling/analysis of A) the forcing of the northern-autumn (Sept. - Oct.) circulation anomalies over the Pacific in order to reveal potential feedback of the anomalous Asian summer-monsoon rainfall on the subsequent El Nino/La Nina development, and B) of the potential extratropical forcing of interannual-variability of the Asian summer-monsoons by Eurasian springtime snow-cover anomalies. The research-tasks include: 1) Estimation of the 3-dimensional diabatic heating field (and transient eddy-flux convergence) from the global ECWMWF-analyses data sets for this diagnostic project is based on operational- analyses rather than GCM simulation of anomalous monsoons. 2) Linear simulations with a multi-layer global steady primitive-equation model linearized about a zonally-varying climatological flow -- a necessary first-step in such dynamical- diagnostic analysis. (Meeting this prerequisite will also allow identification of the most consistent diabatic-heating estimate.) A 'direct-access' adaptation of an LU decomposition method should permit higher linear-model resolution than previously possible. 3) Identification of the characteristic structure of the El Nino-related heating anomalies over the tropical Pacific and Indian oceans during March - May and June - August periods, and a computation of their remote response over Asia. The remote impact of just the Pacific-basin heating anomalies will also be assessed. 4) Calculation of the 'Himalayan-Tibetan orography' - forced anomalous circulation during all recent summers, and an examination of its phase in the Asian lower troposphere vis-a-vis that of the remotely-forced anomalous thermal response. This aspect of the proposed research may help explain the basis for the perplexing threshold-dependence in the Monsoon-El Nino linkage. Results of a pilot study are indicative of the potential insight that such dynamical-diagnostic analysis can provide in improving our understanding of the interactions (and potential feedback) between anomalous Asian summer-monsoons and El Nino/La Nina episodes--the two global-scale climate anomalies whose understanding, simulations and ultimately prediction will be central to the success of the TOGA/GOALS missions.

摘要ATM-9316278 NIGAM，马里兰州苏马特大学 - 大学公园标题：观察到的“亚洲夏季季风降雨的动态诊断 - 埃尔尼诺的关系 - 埃尔尼诺的关系 - 该项目旨在建立动态基础，以在亚洲夏季季前雨/尼娜（El Nino Nino）/尼娜（El Nino Nino）/尼娜（El Nino Nino）中诊断诊断的季节诊断的经验联系起来，以实现年间波动之间的经验联系。在北部夏季和“蒙索前”（3月 - 五月）的季节，亚洲大陆（以及全球热带和室外）的异常。 对下对流层和近表面循环异常的强迫的理解将被强调，因为这对于季风泛滥异常的产生和热带海洋循环异常至关重要。 The project objectives also include diagnostic modeling/analysis of A) the forcing of the northern-autumn (Sept. - Oct.) circulation anomalies over the Pacific in order to reveal potential feedback of the anomalous Asian summer-monsoon rainfall on the subsequent El Nino/La Nina development, and B) of the potential extratropical forcing of interannual-variability of the Asian summer-monsoons by Eurasian springtime雪覆盖异常。 研究任务包括：1）从全局ECWMWF-Analyses数据集中估算3维绝致糖性加热场（和瞬态涡流融合）的估计，该数据集基于操作分析，而不是对Anomalos Monsoons的GCM模拟。 2）具有多层全局稳定原始方程模型的线性仿真线性涉及围绕区域变化的气候流 - 这是这种动态诊断分析的必要第一步。 （满足此先决条件还将允许识别最一致的绝热加热估计值。）LU分解方法的“直接访问”适应应允许比以前更高的线性模型分辨率更高。 3）在3月 - 5月和6月至8月的时期，鉴定了热带太平洋和印度洋与热带太平洋和印度洋的特征结构，以及它们对亚洲的远程响应的计算。 还将评估仅太平洋 - 巴丁加热异常的远程影响。 4）计算“喜马拉雅藏形地形” - 在最近的所有夏天都强迫异常循环，并检查其在亚洲下部对流层中相对于远程异常热反应的相位。 拟议的研究的这一方面可能有助于解释季风 - EL NINO链接中困惑阈值依赖性的基础。 试点研究的结果表明了潜在的见解，即这种动态诊断分析可以提供我们对我们对异常亚洲夏季季风异常相互作用（以及潜在反馈）的理解（以及潜在的反馈）的理解，这两种全球尺度的气候气候对他们的理解，模拟和最终的预测将成为成功的核心/目标。