Uncovering mechanisms behind Chennai's deluges during north-east monsoon season 2015: An observational and modeling analysis

IF 1.9 4区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Dynamics of Atmospheres and Oceans Pub Date : 2024-09-14 DOI:10.1016/j.dynatmoce.2024.101494
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Abstract

The present study delves into the underlying processes responsible for the Chennai deluge during 9th, 15th of November, and 1st December, 2015 by employing both observational data and modeling approaches. The Chennai rainfall, as observed from the GPM satellite data, was substantially higher than the accumulated normal of ∼79 cm for the October-December period. These extreme events coincided with the strongest El Niño event of the century, which persisted from 2014 to early 2016. Further, it is found that the anomalies in Sea Surface Temperature (SST) during this period were more than 1° K above the climatological value and prevailing strong low-level easterly waves over the Indian Oceanic region aided the intensification of previously developing synoptic systems. Soil moisture analysis indicated saturation values nearing 70 %, resulting in increased surface runoff during rainfall events in the backdrop of rapid urban expansion from 1995 to 2015 and aggravated water logging issues. Calculation of thermodynamic indices revealed favourable conditions for the development and intensification of severe convective systems, leading to the catastrophic rainfall events over the Chennai region. A high resolution regional model NCUM (resolution ∼1.5 Km) was utilized to simulate various synoptic features and dynamics of the event over Chennai. Moisture transport at 700 hPa and integrated precipitable water up to 300 hPa were examined, revealing a strong convergence of moisture along the Chennai coast for all cases, with high values of precipitable water observed. Simulations of 3-hourly accumulated rainfall from model generally align with corresponding GPM satellite estimates, despite the model tending to underestimate the intensity of rainfall in all cases. The model simulated location specific rainfall is reasonably well matched with the in-situ observations around Chennai region. However, the model is underestimated the peak rainfall while compare with the observations in all the cases. Further, it successfully depicts the dynamics and structure of extreme rainfall events, including key features such as wind patterns and moisture convergence, demonstrating its utility for forecasting extreme weather events in the Chennai region.

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揭示 2015 年东北季风季节钦奈洪水背后的机制:观测和建模分析
本研究采用观测数据和建模方法,深入研究了 2015 年 11 月 9 日、15 日和 12 月 1 日钦奈暴雨的基本过程。从 GPM 卫星数据观测到的钦奈降雨量大大高于 10 月至 12 月期间的累计正常降雨量 79 厘米。这些极端事件与本世纪最强的厄尔尼诺现象同时发生,厄尔尼诺现象从 2014 年持续到 2016 年初。此外,研究还发现,在此期间,海面温度(SST)的异常值比气候学值高出 1° K 以上,印度洋区域上空盛行的强烈低层偏东气浪助长了先前发展的同步系统的加强。土壤水分分析表明,饱和值接近 70%,在 1995 年至 2015 年城市快速扩张的背景下,降雨事件导致地表径流增加,加剧了水涝问题。热力学指数的计算显示,强对流系统的发展和增强具备有利条件,导致钦奈地区发生灾难性降雨事件。利用高分辨率区域模式 NCUM(分辨率为 1.5 千米)模拟了钦奈上空的各种天气特征和降雨动态。对 700 hPa 的水汽输送和 300 hPa 以下的综合可降水量进行了研究,结果表明,在所有情况下,钦奈沿岸的水汽都有很强的辐合,可降水量也很高。尽管模式在所有情况下都倾向于低估降雨强度,但模式模拟的 3 小时累积降雨量与相应的 GPM 卫星估计值基本一致。模型模拟的特定地点降雨量与钦奈地区附近的实地观测数据相当吻合。不过,与观测结果相比,模型在所有情况下都低估了峰值降雨量。此外,该模型成功地描述了极端降雨事件的动态和结构,包括风型和水汽汇聚等关键特征,证明了其在预报钦奈地区极端天气事件方面的实用性。
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来源期刊
Dynamics of Atmospheres and Oceans
Dynamics of Atmospheres and Oceans 地学-地球化学与地球物理
CiteScore
3.10
自引率
5.90%
发文量
43
审稿时长
>12 weeks
期刊介绍: Dynamics of Atmospheres and Oceans is an international journal for research related to the dynamical and physical processes governing atmospheres, oceans and climate. Authors are invited to submit articles, short contributions or scholarly reviews in the following areas: •Dynamic meteorology •Physical oceanography •Geophysical fluid dynamics •Climate variability and climate change •Atmosphere-ocean-biosphere-cryosphere interactions •Prediction and predictability •Scale interactions Papers of theoretical, computational, experimental and observational investigations are invited, particularly those that explore the fundamental nature - or bring together the interdisciplinary and multidisciplinary aspects - of dynamical and physical processes at all scales. Papers that explore air-sea interactions and the coupling between atmospheres, oceans, and other components of the climate system are particularly welcome.
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