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李莹, 朱伟军, 魏建苏. 冬季北太平洋风暴轴指数的评估及其改进[J]. 大气科学, 2010, 34(5): 1001-1010. DOI: 10.3878/j.issn.1006-9895.2010.05.14
引用本文: 李莹, 朱伟军, 魏建苏. 冬季北太平洋风暴轴指数的评估及其改进[J]. 大气科学, 2010, 34(5): 1001-1010. DOI: 10.3878/j.issn.1006-9895.2010.05.14
LI Ying, ZHU Weijun, WEI Jiansu. Reappraisal and Improvement of Winter Storm Track Indices in the North Pacific[J]. Chinese Journal of Atmospheric Sciences, 2010, 34(5): 1001-1010. DOI: 10.3878/j.issn.1006-9895.2010.05.14
Citation: LI Ying, ZHU Weijun, WEI Jiansu. Reappraisal and Improvement of Winter Storm Track Indices in the North Pacific[J]. Chinese Journal of Atmospheric Sciences, 2010, 34(5): 1001-1010. DOI: 10.3878/j.issn.1006-9895.2010.05.14

冬季北太平洋风暴轴指数的评估及其改进

Reappraisal and Improvement of Winter Storm Track Indices in the North Pacific

  • 摘要: 首先对风暴轴的定义及其强度和位置表征方法进行了归纳总结, 然后利用1958~2001年44年冬季ERA40位势高度场资料重新评估了几种不同的风暴轴特征指数, 分析得到: 这些不同的定义方法在表征风暴轴强度变化方面具有一致性, 但在描述风暴轴的位置变动方面有较大差异。根据冬季北太平洋风暴轴主体的强度和位置变化特征, 提出了一组更为恰当的动态定量的表征方法, 即取北太平洋及其周边区域 (30°N~60°N, 120°E~120°W) 冬季500 hPa位势高度天气尺度滤波方差大于20 dagpm2的所有格点滤波方差的平均值, 以及满足上述条件所有格点的经度平均和纬度平均分别作为冬季北太平洋风暴轴的强度指数 (NII)、经度指数 (NXI) 和纬度指数 (NYI)。通过比较分析, 证明了新定义的指数更能反映风暴轴实际的变动特征。继而利用新指数分析了冬季北太平洋风暴轴的强度和位置的长期变化, 得到以下结论:44年中, 冬季北太平洋风暴轴的强度微弱增加, 且在1970年代中期以前北太平洋风暴轴的强度和位置的年代际变化关系复杂; 1970年代中期以后北太平洋风暴轴的强度和位置的年代际变化具有准协同一致性, 表现为偏弱期位置偏西偏南, 偏强期位置偏东偏北。而且, 这种长期变化与太平洋海气系统成员的低频变化有相关性, 其变化成因是复杂的。

     

    Abstract: Various methods defining the storm track as well as its intensity and location are reviewed and summarized, and each index is reappraised using 44-year (1958-2001) ERA40 geopotential height data in winter. It has been found all these indices are consistent in describing the intensity of storm track, but they are quite different in describing the position. According to the main features of storm track over the North Pacific in winter, using 500-hPa synoptic-scale geopotential height data over the North Pacific and its surrounding areas (30°N-60°N, 120°E-120°W), a method which better defines the storm track indices is proposed, that is, the values at the grid points with variance greater than 20 dagpm2 are averaged as the winter North Pacific storm track intensity index (NII), the average of the longitudes at the grid points is defined as the longitude index (NXI), and the average of the latitudes is defined as the latitude index (NYI). It is proved that the newly defined indices can better reflect the variation of the storm track in this study. It has also revealed that during the period of 1958/1959-2001/2002, the storm track over the North Pacific was slightly strengthened and tended to move southward and westward. The relationship between the strength and location was complicated before the mid-1970s, and it became quasi-consistent after the mid-1970s, with the location northward and eastward in the strong storm track stage, and vice versa. Moreover, such a long-term variation is related to the low-frequency variability of the Pacific sea-air systems, and the causes are sophisticated.

     

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