Abstract

The main goal of the present work is to compare and contrast the characteristics of distinct monsoon systems like the Indian monsoon system (IMS) and South American monsoon system (SAMS) for the period (1979–2022). In addition, we discuss in some detail the theoretical aspects of the two monsoon systems by examining the energetics and the applicability of “convective quasi-equilibrium, (CQE).” We have also analyzed the precipitation interannual variability of SAMS and IMS considering neutral, El Niño, and La Niña years. Then, a discussion of the applicability of CQE along with the recent changes in surface entropy is presented. In our analysis, we found that interannual variability in the case of SAMS is less than that of IMS, and rainfall of SAMS is not drastically affected by ENSO when compared to IMS. We observed that rainfall characteristics over IMS are more complex than SAMS. The annual cycle of the vertically integrated total kinetic energy (K_E) over SAMS is maximum in Austral spring, while the precipitation is higher in Austral summer. This is in sharp contrast to the IMS, where the maximum K_E and rainfall coincide, both occurring in July and August. Further analysis showed that the conversion from the mean available potential energy P_Z to the eddy available potential energy P_E and conversion from P_E to K_E are important over SAMS. This shows that in South America, baroclinic conversions associated with baroclinic instability are important in austral summer, while over IMS, baroclinic conversions are not important in boreal summer. Our results support CQE for the IMS, but in the case of El Niño, we found that CQE is invalid. For SAMS, the applicability of CQE is climatologically doubtful, but during El Niño, the applicability of CQE is robustly visible.

中文翻译：

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印度和南美季风变化及其可能原因的比较

摘要

目前工作的主要目标是比较和对比该时期（1979-2022）印度季风系统（IMS）和南美季风系统（SAMS）等不同季风系统的特征。此外，我们通过研究“对流准平衡（CQE）”的能量学和适用性，详细讨论了两个季风系统的理论方面。我们还分析了中性年、厄尔尼诺年和拉尼娜年的 SAMS 和 IMS 降水年际变化。然后，讨论了 CQE 的适用性以及表面熵的最新变化。在我们的分析中，我们发现 SAMS 的年际变化小于 IMS，并且与 IMS 相比，SAMS 的降雨量并未受到 ENSO 的显着影响。我们观察到 IMS 上的降雨特征比 SAMS 更复杂。SAMS垂直积分总动能( K _E )的年周期在南半球春季最大，而南半球夏季降水量较多。这与 IMS 形成鲜明对比，在 IMS 中，最大K _E和降雨量同时发生，均发生在 7 月和 8 月。进一步分析表明，从平均可用势能P _Z到涡流可用势能P _{E 的}转换以及从P _E到K _E的转换比 SAMS 更重要。这表明在南美洲，与斜压不稳定相关的斜压转换在南半球夏季很重要，而在IMS上，斜压转换在北半球夏季并不重要。我们的结果支持 IMS 的 CQE，但在厄尔尼诺的情况下，我们发现 CQE 无效。对于 SAMS，CQE 的适用性在气候学上值得怀疑，但在厄尔尼诺期间，CQE 的适用性是显而易见的。