| 项目编号: | 1565653
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| 项目名称: | Mechanisms for El Nino and La Nina Evolution Asymmetry and Formation of Super El Ninos |
| 作者: | Tim Li
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| 承担单位: | University of Hawaii
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| 批准年: | 2016
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| 开始日期: | 2016-11-01
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| 结束日期: | 2019-10-31
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| 资助金额: | 496497
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| 资助来源: | US-NSF
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| 项目类别: | Continuing grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Geosciences - Atmospheric and Geospace Sciences
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| 英文关键词: | model
; preliminary work
; work
; difference
; model simulation
; coupled model intercomparison project version
; workforce development
; model amplitude difference
; ocean-atmosphere modeling experiment
; pacific subtropical cell
; atmosphere model
; development phase
; model background state
; simulation
; super event
; la ninas
; la nina event
; few el ninos
; enso event
; el nino
; large portion
; underlying mechanism
; super el ninos
; feedback mechanism
; particular need
; imminent super el nino
; el nino event
; ocean mixed layer heat budget analysis
; abstractel nino/southern oscillation
; change
; el ninos
; ordinary el ninos
; mixed layer heat budget
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| 英文摘要: | ABSTRACT
El Nino/Southern Oscillation (ENSO) events, in which the sea surface temperatures (SSTs) warm or cool over a large portion of the central and eastern equatorial Pacific, affect weather and climate worldwide including substantial impacts over the US. The underlying mechanisms of ENSO have been identified and prediction efforts have met with some success, but fundamental questions remain. One such question is why El Nino events (with anomalously warm SSTs in the equatorial Pacific) terminate differently from La Nina events (with cold SSTs), as El Ninos are often followed by La Ninas while La Ninas are more likely to persist or redevelop. Preliminary work by the PI has identified differences in the pattern of surface fluxes and wind stress in the central Pacific during the mature and decaying phases of El Nino and La Nina events. Work performed here uses a combination of ocean mixed layer heat budget analysis and model simulations (primarily with uncoupled ocean and atmosphere models) to determine the origins of these differences and their importance for differences in event termination.
A second question is why a few El Ninos, termed "super El Ninos", grow rapidly to substantially larger amplitude (over two standard deviations) than typical events. Preliminary work has identified differences in the onset and development phases of super and ordinary El Ninos including off-equatorial thermocline depth anomalies in the super events, and work here examines these differences through a combination of coupled and uncoupled ocean-atmosphere modeling experiments.
A further task of the research is an examination of changes in ENSO amplitude in simulations of greenhouse gas-induced future climate change. A survey of simulations from the Coupled Model Intercomparison Project version 5 (CMIP5) shows substantial disagreement, with roughly equal numbers of models projecting an increase or decrease in the strength of ENSO events. Work here seeks to identify differences in feedback mechanisms (e.g. the Bjerknes feedback) which can account for model to model amplitude differences. Once these are identified they will be related to changes in the model background state through a linear decomposition of the mixed layer heat budget. One hypothesis considered is that amplitude differences are related to changes in the meridional width of the ENSO SST pattern, which is in turn related to the strength of the Pacific Subtropical Cell.
The work has societal broader impacts due to the worldwide consequences of ENSO events and the desirability of improved ENSO predictions. Predictions in 2014 of an imminent super El Nino, which did not materialize, suggest a particular need for better understanding of the nature of super events. Work to improve understanding of how climate change affects ENSO events also has societal value, and the PI intends to develop a projection of ENSO amplitude change based on work under this award. In addition, the project provides support and training for a graduate student, thereby promoting workforce development in this research area. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/90821
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| Appears in Collections: | 全球变化的国际研究计划
科学计划与规划
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| Recommended Citation: | |
Tim Li. Mechanisms for El Nino and La Nina Evolution Asymmetry and Formation of Super El Ninos. 2016-01-01.
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