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Descriptions and mechanisms for 1998/99 regime shift over the North Pacific

1998/99 北太平洋政权更替的描述和机制

基本信息

批准号：
15540417
负责人：
MINOBE Shoshiro
金额：
$ 2.3万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

A number of studies are conducted for a climate change over the North Pacific around 1998/99, as well as climate studies which may be a basis of understanding of such a rapid climate change. Here, some major results are described.The principal investigator of this research proposed previously that climatic regime shifts over the North Pacific appeared to be caused as synchronization between a 20-year oscillation and 50-70-year oscillation. In order to understand some basic mechanism of such resonance, a simple delayed oscillator model with periodic modulation of nonlinear feedback and that with periodic forcing are investigated. The basic mechanism of the nonlinear resonance associated with a concept of threshold has been clarified.It was found that substantial changes of sea-ice occurred around 1998/99 in marginal seas around the North Pacific. In the Bering Sea, spring sea-ice reduced around 1999 in the eastern Bering Sea. This change was likely to be caused by a low-pressure anomaly … More over Alaska. In the Okhotsk Sea, although long-term trend of sea-ice reduction continued until the mid-1990s, in the late 1990s and the early 2000s, sea-ice areas were larger than usual. It was found that for this long-term fluctuation of sea-ice, atmospheric conditions in autumn, not in winter previous studies focused, are important.For large-scale oceanic frontal zones, SST changes including those associated with 1998/99 change were investigated using a newly gridded high-resolution SST data (The dataset is available through the internet. You can find via google with "Minobe Maeda 1dg SST"). It was found that the subtropical front exhibited a large change in 1998/99, but not in the subpolar front. This is in contrast to the 1970s climatic regime shift, when a signal is more prominent in the subpolar front.Also, it is found that the winter strength of the Aleutian Low, which is a major atmospheric circulation changes associated with the regime shifts, exhibits bimodality after removal of a linear trend. This suggests that the nonlinear feedback is important in the climate feedback underlying the regime shifts. Less

对1998/99年前后北太平洋的气候变化进行了一些研究，以及可能成为理解这种快速气候变化的基础的气候研究。主要结果如下：本研究的主要研究者曾提出北太平洋气候体制的变化是由20年振荡和50-70年振荡的同步引起的。为了理解这种共振的一些基本机制，我们研究了一个简单的非线性反馈周期调制的时滞振子模型和一个周期强迫的时滞振子模型。通过对1998 - 1999年北太平洋边缘海海冰变化的分析，发现海冰在1998 - 1999年前后发生了显著的变化。在白令海，1999年左右白令海东部春季海冰减少。这种变化可能是由低压异常引起的 ...更多信息阿拉斯加上空。在鄂霍次克海，虽然海冰减少的长期趋势一直持续到20世纪90年代中期，但在20世纪90年代末和21世纪初，海冰面积比平常大。结果表明，秋季的大气条件对海冰的长期变化起着重要作用，而冬季的大气条件对海冰的长期变化起着重要作用。对于大尺度的海洋锋区，利用新网格化的高分辨率SST资料（该资料可通过互联网获取），研究了SST的变化，包括与1998/99年变化相关的SST变化。你可以通过谷歌找到与“美浓部前田1dg SST”）.结果表明，1998/99年副热带锋变化较大，而副极地锋变化不大。这与20世纪70年代的气候体制转换相反，当时的信号在副极地锋中更为突出。此外，还发现，阿留申低压的冬季强度，这是一个主要的大气环流变化与体制转换，消除线性趋势后，表现出双峰。这表明，非线性反馈是重要的气候反馈的制度转变。少