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首页> 外文期刊>Climate dynamics >The boreal spring variability of the Intra-Americas low-level jet and its relation with precipitation and tornadoes in the eastern United States
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The boreal spring variability of the Intra-Americas low-level jet and its relation with precipitation and tornadoes in the eastern United States

机译：美国东部低空急流的春季北空变化及其与美国东部降水和龙卷风的关系

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摘要

The Intra-Americas Sea (IAS) low-level jet has been studied mainly for the summer and winter seasons. In contrast, spring conditions have been studied less. Here we analyze the boreal spring variability of the IAS low-level jet (IA-LLJ) and its relation with precipitation and tornadic activity in the region of the lower Mississippi, Tennessee and Ohio River basins (MORB). The main mode of variability of the spring IA-LLJ is obtained from a combined principal component analysis of zonal and meridional winds at 925-hPa. The first empirical orthogonal function of the IA-LLJ is a strengthening of the climatological flow with stronger easterlies in the Caribbean and stronger southeasterlies in the Gulf of Mexico. This first mode of variability of the IA-LLJ is related mainly to the Pacific North American (PNA) teleconnection pattern as the PNA modulates the pressure in the southeast region of the U.S. Consequently, there is an increase in precipitation over the MORB region as the moisture fluxes associated with the IA-LLJ increase. Tornadic activity in nine states spanning the MORB region is also significantly related to the IA-LLJ and the PNA index for March, in addition to the Pacific decadal oscillation (PDO) and the Nino indexes. Among the environmental factors that influence tornadic activity are southwesterly wind shear, dry transients at the mid-troposphere, moist transients at low levels, and an increase in convective available potential energy (CAPE). The decadal shifts in MORB precipitation and tornado activity appear to be related to the decadal shift of the IA-LLJ.
机译：美洲海（IAS）低空急流主要在夏季和冬季进行研究。相反，对弹簧条件的研究较少。在这里，我们分析了IAS低空急流（IA-LLJ）的北半球春季变异性及其与密西西比河下游，田纳西州和俄亥俄州河流域（MORB）地区降水和龙卷风活动的关系。春季IA-LLJ的主要变化模式是通过组合在925-hPa的纬向和经向风的主成分分析获得的。 IA-LLJ的第一个经验正交函数是气候流的增强，加勒比地区的东风更强，墨西哥湾的东南风更强。 IA-LLJ的第一种变率模式主要与太平洋北美（PNA）遥相关型有关，因为PNA调节了美国东南部地区的压力。因此，随着MORB区域降水的增加，与IA-LLJ相关的水分通量增加。除太平洋年代际振荡（PDO）和Nino指数外，跨越MORB区域的9个州的龙卷风活动也与3月的IA-LLJ和PNA指数显着相关。影响旋风活动的环境因素包括西南风切变，对流层中部的干燥瞬态，低水平的湿性瞬态以及对流可用势能（CAPE）的增加。 MORB降水和龙卷风活动的年代际变化似乎与IA-LLJ的年代际变化有关。

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  • 来源
    《Climate dynamics》 |2011年第2期|p.247-259|共13页
  • 作者

    Ernesto Munoz; David Enfield;

  • 作者单位

    Rosenstiel School of Marine and Atmospheric Science,Cooperative Institute for Marine and Atmospheric Studies,University of Miami, 4600 Rickenbacker Causeway,Miami, FL 33149, USA;

    rnRosenstiel School of Marine and Atmospheric Science,Cooperative Institute for Marine and Atmospheric Studies,University of Miami, 4600 Rickenbacker Causeway,Miami, FL 33149, USA;

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  • 正文语种 eng
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  • 关键词

    low-level jet; tornadoes; PNA; mississippi river; intra-americas sea;

    机译：低空喷射龙卷风PNA;密西西比河;美洲内海;

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