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首页> 外文期刊>Journal of the Atmospheric Sciences >Interannual Variability of Indian Summer Monsoon arising from Interactionsbetween Seasonal Mean and Intraseasonal Oscillations
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Interannual Variability of Indian Summer Monsoon arising from Interactionsbetween Seasonal Mean and Intraseasonal Oscillations

机译：季节均值和季节内振荡之间相互作用引起的印度夏季风的年际变化

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摘要

A significant fraction of interannual variability (IAV) of the Indian summer monsoon (ISM) is known to be governed by "internal" dynamics arising from interactions between high-frequency fluctuations and the annual cycle. While several studies indicate that monsoon intraseasonal oscillations (MISOs) are at the heart of such internal IAV of the monsoon, the exact mechanism through which MISOs influence the seasonal mean monsoon IAV has remained elusive so far. Here it is proposed that exchange of kinetic energy (KE) between the seasonal mean and MISOs provides a conceptual framework for understanding the role of intraseasonal oscillations (ISOs) in causing IAV and interdecadal variability (IDV) of the ISM. The rate of KE exchange between seasonal mean and ISOs is calculated in frequency domain for each Northern Hemispheric summer season over the ISM domain, using 44 yr of the 40-yr ECMWF Re-Analysis (ERA-40) data. The seasonal mean KE and the rate of KE exchange between seasonal mean and ISO shows a significant relationship at both the 850- and 200-hPa pressure levels. Since the rate of KE exchange between seasonal mean and ISO is found to be independent of known external forcing, the variability in seasonal mean KE arising from this exchange process can be considered as an internal component explaining about 20% of IAV and about 50% of IDV. Contrary to the many modeling studies attributing the weakening of tropical circulation to the sta-bilization of the atmosphere by global warming, this paper provides an alternative view that internal dynamics arising from scale interactions might be playing a significant role in determining the decreasing strength of the monsoon circulation.
机译：已知印度夏季风（ISM）的年际变化（IAV）的很大一部分受高频波动与年周期之间相互作用产生的“内部”动力学的支配。尽管有几项研究表明季风季节内振荡（MISO）是季风内部IAV的核心，但到目前为止，MISO影响季节平均季风IAV的确切机制仍然难以捉摸。在此提出，在季节平均值和MISO之间交换动能（KE）为理解季节内振荡（ISO）在引起ISM的IAV和年代际变化（IDV）中的作用提供了一个概念框架。使用40年ECMWF重新分析（ERA-40）数据中的44年，在ISM域的每个北半球夏季，在频域中计算季节性平均值和ISO之间的KE交换率。在850hPa和200hPa压力水平下，季节平均KE和KE在季节性平均值和ISO之间的交换率均显示出显着的关系。由于发现季节性平均值和ISO之间的KE交换速率与已知的外部强迫无关，因此，可以将由该交换过程引起的季节性平均值KE的变化视为解释IAV约20％和IAV约50％的内部因素。 IDV。与许多将热带环流减弱归因于全球变暖而稳定大气的建模研究相反，本文提供了另一种观点，即尺度相互作用产生的内部动力学可能在确定热带气旋强度下降中起重要作用。季风环流。

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