Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall

Abstract The Indian summer monsoon (ISM) shows quasi-rhythmic intraseasonal oscillations (ISO) manifested as alternate ‘active’ phases of copious rainfall and quiescent phases of ‘break’. Within these periodic phases, the daily rainfall shows large variability and exhibits spatiotemporally sporadic...

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Autores principales:	Nirupam Karmakar, Arindam Chakraborty, Ravi S. Nanjundiah
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/ef66e40fe6894c6585972e728814c2fc
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spelling	oai:doaj.org-article:ef66e40fe6894c6585972e728814c2fc2021-12-02T16:08:11ZIncreased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall10.1038/s41598-017-07529-62045-2322https://doaj.org/article/ef66e40fe6894c6585972e728814c2fc2017-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-07529-6https://doaj.org/toc/2045-2322Abstract The Indian summer monsoon (ISM) shows quasi-rhythmic intraseasonal oscillations (ISO) manifested as alternate ‘active’ phases of copious rainfall and quiescent phases of ‘break’. Within these periodic phases, the daily rainfall shows large variability and exhibits spatiotemporally sporadic extreme rainfall events. The recent decades have witnessed a significant increase in the number of these extreme rainfall events, especially in the quiescent phases. This increase is accompanied by a decreasing trend in the mean monsoon rainfall and a weakening variance of its low-frequency ISO (LF-ISO) cycle. However, any physical link between this apparent paradox of increased extreme rainfall events and weakened slower-time-scale components is not yet reported. Here, using observations and numerical model simulations, we show that the occurrence of extreme rainfall events, primarily in the break phase of an LF-ISO cycle, reduce the intensity of the following active phase by stabilizing the atmosphere. We found that extreme events in a monsoon break leads to a reduction in the vertical shear of zonal winds and an increase in the static stability of the atmosphere in the following break-to-active transition and active phases. These conditions oppose the initiation and development of an active phase and lessen its intensity. This reduces the LF-ISO intensity and mean ISM rainfall.Nirupam KarmakarArindam ChakrabortyRavi S. NanjundiahNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-7 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Nirupam Karmakar Arindam Chakraborty Ravi S. Nanjundiah Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
description	Abstract The Indian summer monsoon (ISM) shows quasi-rhythmic intraseasonal oscillations (ISO) manifested as alternate ‘active’ phases of copious rainfall and quiescent phases of ‘break’. Within these periodic phases, the daily rainfall shows large variability and exhibits spatiotemporally sporadic extreme rainfall events. The recent decades have witnessed a significant increase in the number of these extreme rainfall events, especially in the quiescent phases. This increase is accompanied by a decreasing trend in the mean monsoon rainfall and a weakening variance of its low-frequency ISO (LF-ISO) cycle. However, any physical link between this apparent paradox of increased extreme rainfall events and weakened slower-time-scale components is not yet reported. Here, using observations and numerical model simulations, we show that the occurrence of extreme rainfall events, primarily in the break phase of an LF-ISO cycle, reduce the intensity of the following active phase by stabilizing the atmosphere. We found that extreme events in a monsoon break leads to a reduction in the vertical shear of zonal winds and an increase in the static stability of the atmosphere in the following break-to-active transition and active phases. These conditions oppose the initiation and development of an active phase and lessen its intensity. This reduces the LF-ISO intensity and mean ISM rainfall.
format	article
author	Nirupam Karmakar Arindam Chakraborty Ravi S. Nanjundiah
author_facet	Nirupam Karmakar Arindam Chakraborty Ravi S. Nanjundiah
author_sort	Nirupam Karmakar
title	Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
title_short	Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
title_full	Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
title_fullStr	Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
title_full_unstemmed	Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
title_sort	increased sporadic extremes decrease the intraseasonal variability in the indian summer monsoon rainfall
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/ef66e40fe6894c6585972e728814c2fc
work_keys_str_mv	AT nirupamkarmakar increasedsporadicextremesdecreasetheintraseasonalvariabilityintheindiansummermonsoonrainfall AT arindamchakraborty increasedsporadicextremesdecreasetheintraseasonalvariabilityintheindiansummermonsoonrainfall AT ravisnanjundiah increasedsporadicextremesdecreasetheintraseasonalvariabilityintheindiansummermonsoonrainfall
_version_	1718384629278310400

Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall

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