Tropical Pacific Decadal Variability and Its Impact on the Atmosphere in Climate Models

热带太平洋年代际变率会对全球气候产生巨大影响，并使我们区分人为引起的趋势与自然气候变化的能力复杂化。因此，提高对造成这种变率的机制的了解，对于评估热带海洋的可预测性及其对当地和偏远地区气候的影响至关重要。本研究将利用为政府间气候变化专门委员会第四次评估报告进行的运行，检查热带太平洋地区全球气候模式集合输出中的年代际变率。将确定相关的物理过程及其起源区域，这些区域强迫将与大尺度大气环流有关。该项目还将研究未来气候中可能出现的年代际变化特征，以及这种未来变化对人类重要的气候变化的影响，比如美国的降雨量。这项工作将结合对现有模型输出的深入诊断和使用海洋模型的敏感性实验。鉴于地表风强迫在年代际变化中的核心作用，这些实验将应用不同地区的异常风强迫，以确定在年代际时间尺度上异常风的关键强迫区域和关键方面。对于具有更现实的年代际变化的气候模式，相关的风强迫将与大尺度大气环流有关，以确定该强迫和热带海面温度变化引起的大尺度大气异常的前兆。气候变化模拟将用于研究变暖气候下的年代际变化特征及其全球影响。这项工作的更广泛影响包括与科罗拉多大学的博士生合作。对热带太平洋地区现在和未来气候的年代际变化的进一步了解将有助于评估美国持续干旱的可预测性。

Tropical Pacific decadal variability can have large impacts upon the global climate, and it complicates our ability to separate anthropogenically induced trends from natural climate variations. Improved understanding of the mechanisms responsible for such variability is, therefore, fundamental for assessing the predictability of the tropical oceans and their local and remote climate influences. This study will examine tropical Pacific decadal variability in the output of an ensemble of global climate models using runs carried out for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Relevant physical processes will be identified, along with their regions of origin, and these regional forcings will be related to the large-scale atmospheric circulation.The project will also examine the features of decadal variability likely to emerge in future climates, along with the impacts of this future variability on climate variations important to people, such as rainfall over the United States. The work will use a combination of in-depth diagnostics of existing model output and sensitivity experiments using an ocean model. Given the central role of surface wind forcing for decadal variations, these experiments will apply anomalous wind forcing in different areas, in order to identify key forcing regions and key aspects of the anomalous winds at decadal timescales. For climate models with more realistic decadal variations, the associated wind forcing will be related to the large-scale atmospheric circulation to identify precursors of that forcing and large-scale atmospheric anomalies resulting from the tropical sea surface temperature variations. Climate change simulations will be used to examine the characteristics of decadal variability in a warmer climate, along with its global influences.Broader impacts of this work include collaboration with a Ph.D. student at the University of Colorado. Improved understanding of tropical Pacific decadal variability in present and future climates will help in assessing the predictability of persistent droughts over the United States.