中纬度西风带轨道尺度演化的长期瞬变模拟研究

The boreal mid-latitude westerly as an important link between mid-high latitude, the North Atlantic and the Asian monsoon region, has received widespread attentions from paleoclimate and pleoenvironmental researchers. Despite major advances in the last few decades in characterizing and understanding these climate phenomena, disagreements persist relative to the forcing mechanisms and interactions. In this project, some long-term transient simulations will be conducted using the latest Community Earth System Model (CESM1.0) and the orbital acceleration technique, driven by the different forcing factors such as the insolation change caused by Earth's orbital, atmospheric concentration of greenhouse gases, global ice volume，to analyze the strength and location of the westerly zone during the past multiple precession cycles. We will evaluate the long-term evolution mechanisms and major regulatory factors of the westerly zone at the orbital scale, based on high-resolution numerical experiments considering the thermohaline circulation and dust cycle elements, by cross- comparing and examining the geological records and the results of numerical experiments. The aims of this project are to clarify the relationships between the mid-latitude westerly zone, Asian inland drought, and the Asian monsoon, at orbital scale. We expected these research results have more important theoretical significance and reference value.

北半球中纬度西风带作为联系中高纬、北大西洋和亚洲季风的一个重要纽带，近年来受到古气候古环境研究者的广泛关注，但有关其轨道尺度驱动机制及其对亚洲内陆干旱化和亚洲季风强弱的影响机制仍存在较大争议。本项目利用最新一代地球系统模式CESM1.0，采用轨道强迫加速技术，完成一系列包含多个岁差周期在内的日射变化、大气温室气体含量、全球冰量等强迫因子长期瞬变数值试验，分析轨道尺度上西风带强弱、南北迁移扰动特征及其影响机制。通过地质记录-模拟结果的交叉检验和综合对比，开展综合考虑温盐环流、粉尘循环等高分辨率试验，深入理解轨道尺度上西风带长期演化特征和内外主控因子，厘清轨道尺度上中纬度西风带、内陆干旱化、亚洲季风的相互关系，可望获得一些具有理论意义和参考价值的创新性研究成果。

中纬度西风急流是北半球一个重要环流因子，其强弱变化和急流轴位置南北摆动对区域气候、沙尘循环均会产生重要影响。本项目通过一系列长期瞬变数值试验、敏感性数值试验，系统分析了轨道尺度上西风环流长期演化特征，结合地质记录探讨了轨道尺度上西风带特征、高原热动力作用、东亚季风以及沙尘循环的相互作用及其形成机制。主要结论如下：1）进一步确定青藏高原隆升对东亚夏季风轨道尺度气候的放大作用，模拟指出有、无青藏高原是引起轨道尺度东亚区域南北降水反相位的主要原因；2）模拟分析过去15万年西风带对中亚沙尘循环的调控机制，指出高日射阶段春季高原热源异常引起高原北侧西风急流增强进而促使中亚干旱区沙尘活动加强；3）敏感性试验结果显示春季高原热源异常是决定高空西风急流强弱和急流轴位置南北摆动的主要原因。