Westward Generation of Eastward-Moving Tropical Convective Bands in TOGA COARE
Westward Generation of Eastward-Moving Tropical Convective Bands in TOGA COARE
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TOGA COARE 东移热带对流带西行
DOI：
10.1175/1520-0469(2001)058
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发表时间：
2001
影响因子：
3.1
通讯作者：
T. Satomura
中科院分区：
文献类型：
--
作者：
S. Shige;T. Satomura
利用一个二维数值云模式研究了热带海洋和全球大气耦合海气响应试验（TOGA COARE）中向西移动的热带对流带产生的机制。在TOGA COARE期间对流活跃日的环境中，成功地模拟了一个老的东移对流带以西的新对流带的顺序生成，其特征是低层西风和高空强东风。新对流带的向西生成可用重力波机制来解释。两个向西传播模式激发下的对流单体相对于对流带向西移动似乎发挥了重要作用。慢传播模式（; 15 ms 21）被浅对流带激发，输送到包含其临界水平的小Richardson数不稳定层下的对流层中。由深对流带激发的快速传播模式（;25 m s21）在对流层中的对流单体的剩余区域包含其临界水平下被输送。这两种模式向西水平传播，并促进浅层对流发展为长寿命对流带。一个干燥的模式与热强迫对流单体表明，向西传播的对流单体下方的波的优先激发是由于向西运动和对流单体的Ascension。没有临界水平的对比模拟证实了所提出的重力波机制。
Mechanisms responsible for westward generation of eastward-moving tropical convective bands in the Tropical Ocean and Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment (TOGA COARE) are investigated using a two-dimensional numerical cloud model. Sequential generation of new convective bands to the west of an old eastward-moving convective band is successfully simulated in an environment of a convectively active day during TOGA COARE, characterized by west winds at low levels and strong easterlies aloft. It is concluded that the westward generation of new convective bands is explained by a gravity wave mechanism. Two westward-propagating modes excited below the convective cells moving westward relative to the convective bands appear to play an important role. A slow-propagating mode (; 15 ms 21) excited by a shallow convective band is ducted in the troposphere under an unstable layer of small Richardson number containing its critical level. A fast-propagating mode ( ;25 m s21) excited by a deep convective band is ducted in the troposphere under the remaining region of the convective cell containing its critical level. These two modes propagate horizontally to the west and promote the growth of shallow convection into long-lived convective bands. A dry model with thermal forcing representing the convective cell showed that preferential excitation of westward-propagating waves below the convective cell is due to westward motion and ascension of the convective cell. A comparative simulation without the critical level confirms the proposed gravity wave mechanism.