Recent changes in the spatio-temporal characteristics of monsoon intraseasonal oscillations

• Published in: Theoretical and applied climatology Vol. 147; no. 1-2; pp. 251 - 264
• Main Authors: Joseph, Susmitha, Sahai, A. K., Shabu, Hindhiya, Chattopadhyay, R., Kaur, Manpreet
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 2022; Springer; Springer Nature B.V
• Subjects: 21st century; Analysis; Aquatic Pollution; Asymmetry; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climate change; Climate science; Climatology; Distribution; Earth and Environmental Science; Earth Sciences; Global warming; Intraseasonal oscillation; Madden-Julian oscillation; Monsoons; Oceans; Original Paper; Oscillations; Rain; Rain and rainfall; Rainfall; Seasonal variations; Skewed distributions; Spatial distribution; Summer monsoon; Temporal variability; Temporal variations; Waste Water Technology; Water Management; Water Pollution Control; Wind; Winds
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-021-03830-7

Monsoon intraseasonal oscillations (MISOs) define a significant proportion of intraseasonal variability of the Indian summer monsoon. In the backdrop of increasing temperatures related to global warming, it is expected that MISOs would exhibit more spatio-temporal variability, prompting an increased frequency of extreme events. Hence, the present study investigates the observed changes in the characteristics of long (≥ 7 days) and short (< 7 days) active and break spells in the early twenty-first century (2001–2019) in comparison with the late twentieth century (1982–2000).
In the recent period, a decreased (increased) frequency of the short (long) active/break spells along with a strengthening of short spells has been noticed. An east–west asymmetry in the spatial distribution of rainfall is further noted with western India experiencing intensified (weakened) active (break) spells. Contrariwise, the central and eastern parts of the country witness weakening (intensification) of active (break) spell in the early twenty-first century. A comprehensive composite investigation of various dynamical and thermodynamical parameters reveals an increase in the strength of low-level winds in the Arabian Sea, thereby increasing the moisture convergence and instability over the western Indian region and the nearby oceanic regions, resulting in the observed east–west asymmetry in the rainfall spatial distribution. Increased intensity of the equatorial Madden–Julian oscillation and its coupling with the northward propagating MISO spells seem to play a pivotal role in lengthening the active/break spells. It is speculated that such changes are triggered by the amplified temperatures over the global oceans in the recent period.