The evolution of sub-monsoon systems in the Afro-Asian monsoon region during the Holocene– comparison of different transient climate model simulations
The evolution of sub-monsoon systems in the Afro-Asian monsoon region during the Holocene– comparison of different transient climate model simulations
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DOI：
10.5194/cp-11-305-2015
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发表时间：
2014-05
影响因子：
4.3
通讯作者：
A. Dallmeyer;M. Claussen;N. Fischer;K. Haberkorn;S. Wagner;M. Pfeiffer;Liya Jin;V. Khon;Yang W
中科院分区：
文献类型：
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作者：
A. Dallmeyer;M. Claussen;N. Fischer;K. Haberkorn;S. Wagner;M. Pfeiffer;Liya Jin;V. Khon;Yang W
最近提出的全球季风假说将季风系统解释为一个全球尺度大气翻转环流的一部分，这意味着区域季风系统与所有北半球季风在年度时间尺度上的同相行为之间存在联系(Trenberth等人，2000年)。这一概念是否适用于过去的气候和较长时间尺度上的变化仍在争论中，因为季风系统表现出不同的区域特征，如不同的季节性(即开始、高峰和退出)。为了研究前工业全新世不同季风系统之间的相互联系，我们分析了5个瞬变全球气候模式对亚非季风区不同子区的降水趋势和变率的影响。我们的分析表明，在具有不同轨道作用力的千禧年时间尺度上，季风并不表现为一个紧密相连的全球系统。根据模式，印度季风和北非季风是耦合的，所有模式都表现出相似的降水趋势和百年降水变率的中等相关性。东亚季风在全新世期间独立变化。季风子系统季节性的不同，导致北非和印度季风系统对全新世日照强迫的响应比东亚季风强，并影响全新世降水变化的季节分布。在印度和北非季风区内，降水只在夏季变化，表现出全新世降水减少的趋势。在东亚季风区，降水信号是由春季降水增加趋势和夏季降水变化减少决定的，两者部分平衡。综合重建和模式结果，并未发现不同季节对不同亚季风系统中全新世降水最佳时间的影响。相反，它们指示了局部不均匀的降水变化，并表明不应使用单一的古记录来描述整个季风子系统的降雨量变化和季风演变。
The recently proposed global monsoon hypothesis interprets monsoon systems as part of one global-scale atmospheric overturning circulation, implying a connection between the regional monsoon systems and an in-phase behaviour of all northern hemispheric monsoons on annual timescales (Trenberth et al., 2000). Whether this concept can be applied to past climates and variability on longer timescales is still under debate, because the monsoon systems exhibit different regional characteristics such as different seasonality (i. e. onset, peak and withdrawal). To investigate the interconnection of different monsoon systems during the pre-industrial Holocene, five transient global climate model simulations have been analysed with respect to the rainfall trend and variability in different sub-domains of the Afro-Asian monsoon region. Our analysis suggests that on millennial timescales with varying orbital forcing, the monsoons do not behave as a tightly connected global system. According to the models, the Indian and North African monsoons are coupled, showing similar rainfall trend and moderate correlation in centennial rainfall variability in all models. The East Asian monsoon changes independently during the Holocene. The dissimilarities in the seasonality of the monsoon sub-systems lead to a stronger response of the North African and Indian monsoon systems to the Holocene insolation forcing than of the East Asian monsoon and affect the seasonal distribution of Holocene rainfall variations. Within the Indian and North African monsoon domain, precipitation solely changes during the summer months, showing a decreasing Holocene precipitation trend. In the East Asian monsoon region, the precipitation signal is determined by an increasing precipitation trend during spring and a decreasing precipitation change during summer, partly balancing each other. A synthesis of reconstructions and the model results do not reveal an impact of the different seasonality on the timing of the Holocene rainfall optimum in the different sub-monsoon systems. Rather they indicate locally inhomogeneous rainfall changes and show that single palaeo-records should not be used to characterise the rainfall change and monsoon evolution for entire monsoon sub-systems.