Contrasting the Indian and East Asian monsoons: implications on geologic timescales
Contrasting the Indian and East Asian monsoons: implications on geologic timescales
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DOI：
10.1016/s0025-3227(03)00196-8
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发表时间：
2003-09
期刊：
影响因子：
2.9
通讯作者：
Bin Wang;S. Clemens;Ping Liu
中科院分区：
文献类型：
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作者：
Bin Wang;S. Clemens;Ping Liu
阿拉伯海和中国南海的表层风分别是印度季风和东亚季风强度的有意义的指标。通过对这两个季风区沉积物记录的分析，研究了古季风的变异性。为了便于解释这些记录，我们通过对比印度部分(40-105°E)和东亚部分(105-160°E)上的季风这两个子系统的年周期和年际变化，重点研究了季风系统的“内部”和“外部”强迫的影响。这些子系统内的年周期差异主要是由于决定大气对太阳强迫的反应的不同陆地-海洋配置造成的。因此，驱动季风年度循环强度的因素与控制古季风变异性的外部(地理和轨道)强迫具有共同的特征。结果表明，这两个季风子系统年际变化的差异主要是由于大气-海洋-陆地耦合系统的内部因素，如厄尔尼诺/拉尼娜的远程影响和局地季风-海洋相互作用。在年际到年代际时间尺度上运行的机制可能与在地质/轨道时间尺度上的机制根本不同。东亚和澳大利亚的低层气流基本上是由地理强迫形成的。在太阳进动增强期间，澳大利亚夏季风的增强可能是由东亚冬季风增强引起的，而不是像在年际时间尺度上那样跟随印度夏季风增强。研究还发现，厄尔尼诺对阿拉伯海的低层气流影响较小，而对南中国海的低层气流影响较大。因此，太平洋热力条件的巨大变化可能会显著改变东亚季风的强度，但不会改变印度季风的强度。
The surface winds over the Arabian Sea and South China Sea are meaningful indicators for the strength of the Indian monsoon and East Asian monsoon, respectively. Paleo-monsoon variability has been studied through analysis of sediment records from these two monsoon regions. To facilitate interpretation of these records, we focus on the impacts of ‘internal’ and ‘external’ forcing of the monsoon system by contrasting the annual cycle and interannual variability of two subsystems: the monsoon over the Indian sector (40–105°E) and over the East Asian sector (105–160°E). Differences in the annual cycle within these subsystems arise primarily from the different land–ocean configurations that determines atmospheric response to the solar forcing. Thus factors that drive intensities of the monsoonal annual cycle share common features with the external (geographic and orbital) forcing that controls paleo-monsoon variability. We show that the differences in interannual variations between the two monsoon subsystems are primarily due to internal factors of the coupled atmosphere–ocean–land system, such as remote impacts of El Niño/La Niña and local monsoon–ocean interactions. The mechanisms that operate on interannual to interdecadal timescales may differ fundamentally from that on geologic/orbital timescales. The low-level flows over the East Asia and Australia are essentially established by geographic forcing. The amplification of the Australia summer monsoon during increased solar precession is likely caused by an enhanced East Asian winter monsoon, rather than following an enhanced Indian summer monsoon as on the interannual timescale. It is also found that El Niño influences the low-level flow moderately over the Arabian Sea but to a greater extent over the South China Sea. As such, large changes in the Pacific thermal conditions may significantly alter the intensity of the East Asian monsoon but not the Indian monsoon.