Interdecadal changes in the storm track activity over the North Pacific and North Atlantic
Interdecadal changes in the storm track activity over the North Pacific and North Atlantic
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DOI：
10.1007/s00382-011-1188-9
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发表时间：
2012-07
期刊：
影响因子：
4.6
通讯作者：
Sun‐Seon Lee;June‐Yi Lee;Bin Wang;K. Ha;K. Heo;F. Jin;D. Straus;J. Shukla
中科院分区：
文献类型：
--
作者：
Sun‐Seon Lee;June‐Yi Lee;Bin Wang;K. Ha;K. Heo;F. Jin;D. Straus;J. Shukla
对1948-2009年NCEP-NCAR I再分析资料和1958-2001年ECMWF ERA-40再分析资料的分析揭示了北方半球热带外风暴轴活动和平均气流-瞬变涡动相互作用的年代际变化特征。首先，在北太平洋风暴轴（PST）和北大西洋风暴轴（AST）的活动在北方冷季（从11月到3月）最显着的转变发生在20世纪70年代初至中期的全球加强的特点，已经注意到在以前的研究。第二，隆冬的太平洋海温活动经历了从80年代初的弱体制到80年代末的强体制的年代际变化。第三，近十年来，早春PST强度增强，而隆冬AST强度减弱。最后，PST和AST活动以及风暴轴活动与气候指数之间的关系也存在年代际变化。风暴轴活动的变化与太平洋年代际涛动和北大西洋涛动在20世纪80年代初之前有很好的相关性，但这种关系之后消失了，PST和AST活动之间的显着联系也被解耦。为了更好地理解70年代中期风暴轴活动和平均气流-瞬变涡动相互作用的转变，本文通过分析局地正压和斜压能量作了进一步的研究。20世纪70年代中期以后全球风暴轴活动的加强主要与平均纬向温度梯度的增强有关，这为斜压涡旋的发展提供了有利条件。与风暴轴活动的变化相一致，北太平洋和北大西洋的斜压能量转换显着增加。PST和AST活动的加强，反过来，有助于加强对流层中高层环流的变化，但对低层温度场的变化有干扰作用。
Analysis of NCEP-NCAR I reanalysis data of 1948–2009 and ECMWF ERA-40 reanalysis data of 1958–2001 reveals several significant interdecadal changes in the storm track activity and mean flow-transient eddy interaction in the extratropics of Northern Hemisphere. First, the most remarkable transition in the North Pacific storm track (PST) and the North Atlantic storm track (AST) activities during the boreal cold season (from November to March) occurred around early-to-mid 1970s with the characteristics of global intensification that has been noticed in previous studies. Second, the PST activity in midwinter underwent decadal change from a weak regime in the early 1980s to a strong regime in the late 1980s. Third, during recent decade, the PST intensity has been enhanced in early spring whereas the AST intensity has been weakened in midwinter. Finally, interdecadal change has been also noted in the relationship between the PST and AST activities and between the storm track activity and climate indices. The variability of storm track activity is well correlated with the Pacific Decadal Oscillation and North Atlantic Oscillation prior to the early 1980s, but this relationship has disappeared afterward and a significant linkage between the PST and AST activity has also been decoupled. For a better understanding of the mid-1970s’ shift in storm track activity and mean flow-transient eddy interaction, further investigation is made by analyzing local barotropic and baroclinic energetics. The intensification of global storm track activity after the mid-1970s is mainly associated with the enhancement of mean meridional temperature gradient resulting in favorable condition for baroclinic eddy growth. Consistent with the change in storm track activity, the baroclinic energy conversion is significantly increased in the North Pacific and North Atlantic. The intensification of the PST and AST activity, in turn, helps to reinforce the changes in the middle-to-upper tropospheric circulation but acts to interfere with the changes in the low-tropospheric temperature field.