阿留申低压四种环流指数的分析和比较
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南京信息工程大学 大气科学学院,江苏 南京 210044


Analysis and comparison of four kinds of circulation indices of Aleutian Low
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School of Atmospheric Sciences,NUIST,Nanjing 210044,China

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    摘要:

    分析和比较了20世纪90年代以来不同学者提出的阿留申低压(Aleutian Low,AL)四种强度指数(Ii,i=1,4〖TX-〗)、两种中心位置指数(〖WTBX〗λi〖WTB1〗、〖WTBX〗φi〖WTB1〗,i=3、4)的时频特征及其与同期北半球太平洋海面温度、气温、降水的相关联系。结果表明:1)强度指数Ii、i=2,4〖TX-〗演变特征最相似;20世纪70年代中期之前AL偏弱,之后AL偏强;近年来又出现AL偏弱趋势。因I1为5个月平均场中AL的强度指数,故它与Ii、i=2,4〖TX-〗差别较大。2)两种中心位置指数地理分布区域(〖WTBX〗λ〖WTB1〗c3,〖WTBX〗φ〖WTB1〗c3)大于(〖WTBX〗λ〖WTB1〗c4,〖WTBX〗φ〖WTB1〗c4),这与平均时段长短及中心位置指数定义差别有关。〖WTBX〗λ〖WTB1〗c4由偏西转向偏东较〖WTBX〗λ〖WTB1〗c3提早约5 a,它与Ii、i=2,4〖TX-〗的一致性更好。3)在强El Ni〖AKn~D〗o事件中,AL加强、中心位置偏东,强La Ni〖AKn~D〗a事件则相反。强度指数I2、I4和位置指数〖WTBX〗λ〖WTB1〗c4反映上述关系较好。4)AL偏强、偏东年,中纬北太平洋区域低温、少雨,北太平洋东北部至北美西北部气温偏高、降水偏多,而北美南部气温偏低、降水偏少;反之亦然。

    Abstract:

    The timefrequency characteristics of four intensity indices Ii(i=1,4〖TX-〗)and two center position indices (〖WTBX〗λ〖WTB1〗i,〖WTBX〗φ〖WTB1〗i;i=3,4〖TX-〗)of the Aleutian low(AL) proposed by different scholars since the 1990s are analyzed and compared in this paper,and their correlation relationships with the sea surface temperature(SST) of the Pacific Ocean,air temperature and precipitation in the Northern Hemisphere during the same period are investigated.The results show that evolutionary features of Ii(i=2,4〖TX-〗) are mostly similar:the AL was weaker before the mid1970s,then stronger,and becomes weaker again in recent years;larger differences existed between I1 and Ii(i=2,4〖TX-〗) probably because I1 is defined according to the 5month mean pressure field.The geographic distributive range of the appearance of the center position of the AL determined by (〖WTBX〗λ〖WTB1〗c3,〖WTBX〗φ〖WTB1〗c3) is larger than that by (〖WTBX〗λ〖WTB1〗c4,〖WTBX〗φ〖WTB1〗c4),which might be caused by the differences in the length of average time period and the different definitions of the center position between them;and it is about 5yr earlier for 〖WTBX〗λ〖WTB1〗c4 to turn from the negative position anomaly phase to the positive one than the time when 〖WTBX〗λ〖WTB1〗c3 did,and the tuning time of 〖WTBX〗λ〖WTB1〗c4 is also more consistent with the transition time of intensity indices Ii(i=2,4〖TX-〗).In strong EI Ni〖AKn~D〗o events,the AL strengthened with its center shifting eastward;and vice versa in La Ni〖AKn~D〗a events.In this respect,intensity indices I2 and I4 and position indices〖WTBX〗 λ〖WTB1〗c4 and 〖WTBX〗λ〖WTB1〗c3 are comparatively better.When the AL was stronger (〖WTBX〗〖AKI~〗′〖WTB1〗i<0) and lay eastward of its normal position (〖WTBX〗〖AKλ~〗〖WTB1〗′ci>0),it was colder and drier in the midlatitude North Pacific region and the southern area of North America,but warmer and wetter in the northeast area of North Pacific,and vice versa.

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  • 收稿日期:2010-05-12
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