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A hybrid Lagrangian/Eulerian view of the global atmospheric mass circulation: Seasonal cycle.

机译：全球大气质量环流的拉格朗日/欧拉混合观点：季节性周期。

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摘要

In this study, we have diagnosed diabatic heating, meridional adiabatic mass and angular momentum transport, and downward transfer of westerly angular momentum by the pressure torque in isentropic coordinates using daily NCEP-NCAR reanalysis II dataset for 32 years from January 1, 1979 to December 31, 2010. Mass and its associated angular momentum fluxes of instantaneous flow depict a snapshot of mass and angular momentum circulations at that time in the Lagrangian perspective, although they are calculated on the Eulerian latitude-longitude coordinates. The hybrid Lagrangian/Eulerain view of instantaneous flow enables us to delineate how the diabatic heating and the pressure torque drive the local change of air mass and its angular momentum via the meridional mass circulation.;One broad hemispheric cell of the meridional mass circulation exists in each hemisphere, which links the tropics to the extratropics and the troposphere to the stratosphere. Warm air mass heated by the diabatic heating in the tropics flows poleward to the extratropics where it sinks by the diabatic cooling. Cold air mass moves back to the tropics by adiabatic equatorward returning flow and diabatic heating near the ground. The air in the poleward branch moves in a down-gradient direction of earth angular momentum whereas the equatorward cold air branch is in an up-gradient direction of earth angular momentum.;Embedded in the hemispheric mass circulation are three distinct but connected cells: the tropical Hadley cell, the stratospheric cell (part of Brewer-Dobson circulation in the winter hemisphere), and the extratropical Hadley cell. In the warm air branch of the tropical Hadley cell, poleward angular momentum transport associated with poleward mass fluxes is responsible for intensification of the subtropical jet. The excessive westerly angular momentum of the subtropical jet slows down significantly the poleward advancement of warm air mass as air mass mostly moves towards the east instead of the pole. As the air mass circulates around the subtropical latitudes, air experiences radiative cooling, resulting in downward cross-isentropic mass and angular momentum fluxes. Part of downward mass transport in the subtropics then joins the poleward warm air branch of the extratropical Hadley cell, connecting two tropospheric circulation cells. The remaining part continues to downward crossing isentropic surfaces and merges with the returning cold air branch of the extratropical Hadley cell. The merged air mass together moves equatorward diabatically (and with small portion adiabatically) as the returning flow of the tropical Hadley cell. In the cold air branch of the tropical Hadley cell, the surface frictional torque and mountain torque play a major role in adding the westerly angular momentum to the equatorward returning flow.;In the extratropics, the meridional mass circulation is carried out mainly by the baroclinically amplifying (or westward tilted) waves. The westward tilted waves in the extratropical stratosphere account for a net poleward transport of air mass and its angular momentum aloft and a net equatorward transport of air mass and its angular momentum below, as well as a net downward transfer of westerly angular momentum by the pressure torque. As the warm air branch of the tropical Hadley cell, poleward transport of angular momentum aloft gives rise to the intensification of the stratospheric polar jet that in turn slows down the poleward mass transport into the polar region. More intense westward tilted wave activities near the polar jet act to remove the excessive westerly angular momentum aloft by the pressure torque. It helps to pave the way for further poleward mass transport in the warm air branch of the stratospheric circulation to overcome the increment of westerly angular momentum during the poleward air mass advancement. The westward tilted waves in the extratropical upper troposphere do the same thing, and are responsible for the extratropical Hadley cell. Strong downward mass transport from the stratosphere to the troposphere in the extratropics results in (1) much weaker equatorward returning flow in the lower stratosphere than poleward warm air flow in the upper stratosphere and (2) stronger equatorward returning flow of the extratropical Hadley cell than poleward warm air branch of the extratropical Hadley cell. In the cold air branch of the extratropical Hadley cell, the gain of angular momentum transferred from the layers above by the pressure torque helps to pave the way for further equatorward mass transport to overcome the lack of westerly angular momentum on the way to the lower latitudes. The equatorward returning flow of the extratropical Hadley cell is connected to that of the tropical Hadley cell in the subtropics by the diabatic heating near the ground.
机译：在这项研究中，我们使用1979年1月1日至12月的每日32年NCEP-NCAR再分析II数据集，诊断了等熵坐标中绝热加热，子午绝热质量和角动量传输以及西风角动量通过等熵坐标中的压力转矩向下传递的情况。 2010年3月31日。质量和与之相关的瞬时流角动量通量以拉格朗日的角度描绘了当时的质量和角动量环流的快照，尽管它们是根据欧拉纬度-经度坐标计算的。拉格朗日/欧拉混合瞬时流视图使我们能够描述绝热加热和压力转矩如何通过子午质量循环驱动空气质量及其角动量的局部变化。；存在一个子午质量循环的宽半球单元每个半球，将热带与温带气层相连，对流层与平流层相连。在热带地区，由非绝热加热所加热的温暖空气团向极地流向温带，在热带地区因非绝热冷却而下沉。绝热的赤道返回气流并靠近地面的绝热加热使冷空气团返回热带。极向支路中的空气沿地球角动量的下降方向移动，而赤道朝冷空气支路沿地球角动量的向上方向移动。嵌入半球质量循环的是三个不同但相互连接的单元：热带Hadley细胞，平流层细胞（冬季半球的Brewer-Dobson循环的一部分）和温带Hadley细胞。在热带Hadley单元的暖空气分支中，与极向质量通量相关的极向角动量传输是引起副热带急流的加剧的原因。亚热带喷流的过大的西风角动量极大地减慢了暖空气团的向极前进，因为空气团大多向东移动而不是向极移动。当空气质量在亚热带纬度周围循环时，空气会受到辐射冷却，从而导致向下的等熵质量和角动量通量下降。然后，亚热带地区向下的质量输运的一部分加入了温带哈德利单元的极向暖空气分支，连接了两个对流层环流单元。其余部分继续向下穿过等熵表面，并与温带哈德利单元返回的冷空气分支合并。合并的空气团一起随着热带哈德利单元的回流而绝热地（赤道地绝热地）向赤道运动。在热带Hadley单元的冷空气分支中，表面摩擦转矩和山地转矩在向赤道返回流中增加西风角动量方面起着主要作用。在温带中，子午质量循环主要由斜压进行放大（或​​向西倾斜）波浪。在温带平流层中向西倾斜的波浪造成了空气质量的净向极极输送和其角动量的上升，以及空气质量的赤道净输送和其下方的角动量，以及西风角动量的净向下传递。扭矩。作为热带Hadley单元的暖空气分支，高空角动量的极向传输引起平流层极地射流的强化，进而减弱了极向质量向极区的传输。极地急流附近更强烈的向西倾斜波活动起着消除压力扭矩作用的过高西风角动量的作用。这有助于为平流层环流的暖空气分支中进一步向极向质量传输铺平道路，以克服在向极空气质量前进过程中西风角动量的增加。温带对流层上的西向倾斜波也做同样的事情，并负责温带哈德利单元。从平流层到平流层的强烈向下传质导致（1）平流层下部的赤道返回流比平流层上部的极向温暖气流弱得多；（2）温带的哈德利单元的赤道返回流比平流层强。温带哈德利细胞的极向温暖空气分支。在温带哈德利单元的冷空气分支中，通过压力扭矩从上方各层传递来的角动量的增益有助于为进一步的赤道质量传递铺平道路，从而克服了通往低纬度方向上缺乏西风角动量的需要。 。通过近地层的绝热加热，亚热带的哈德利细胞的赤道回流与亚热带的热带哈德利细胞的赤道回流相连。

著录项

  • 作者

    Shin, Chul-Su.;

  • 作者单位

    The Florida State University.;

  • 授予单位 The Florida State University.;
  • 学科 Atmospheric sciences.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 143 p.
  • 总页数 143
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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