Easterly waves and ocean–atmospheric oscillations associated with contrasting northeast monsoon seasons over India

The variability of synoptic conditions including the propagation of easterly waves (EWs) along with the ocean–atmospheric oscillations such as El Niño and the Indian Ocean dipole (IOD) associated with the large excess, large deficient and normal northeast monsoon (NEM) over the south peninsular Indi...

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Bibliographic Details
Published in:Journal of Earth System Science 2022-03, Vol.131 (1), p.52, Article 52
Main Authors: Reba, R M, Pattanaik, D R, Raju, P V S
Format: Article
Language:English
Subjects:
Atmospheric oscillations
Convergence
Datasets
Dipoles
Earth and Environmental Science
Earth Sciences
Easterlies
Easterly waves
El Nino
El Nino phenomena
La Nina
Moisture
Monsoons
Oceans
Oscillations
Outflow
Rainfall
Seasons
Space Exploration and Astronautics
Space Sciences (including Extraterrestrial Physics
Synoptic conditions
Wave propagation
Westerlies
Wind
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Summary:The variability of synoptic conditions including the propagation of easterly waves (EWs) along with the ocean–atmospheric oscillations such as El Niño and the Indian Ocean dipole (IOD) associated with the large excess, large deficient and normal northeast monsoon (NEM) over the south peninsular India and particularly over Tamil Nadu (TN) met-subdivision during 2015, 2016 and 2017, respectively, have been investigated. It is seen that a strong El Niño and positive IOD exist during the excess NEM season of 2015 and was dominated by anomalous low-level easterly wind over the equatorial Indian Ocean (EIO), whereas, weak (strong) La Nina and negative IOD conditions prevailed during NEM 2016 (2017) was dominated with anomalous strong (weak) westerlies over EIO. Southward shifting of sub-tropical westerly jet (STWJ), presence of a secondary upper-level divergent outflow over eastern EIO and positive moisture convergence over the TN met subdivision are seasonal mean features observed during large excess NEM 2015. NEM 2016 (2017) is marked with absence of southward latitudinal shift of STWJ and negative (positive) moisture convergence over TN met-subdivision. Further, it is also seen that many active rainfall spells during NEM 2015 and 2017 over TN met-subdivision were associated with passage of EWs over the southern peninsula along east of 85°E, whereas, the large deficient NEM of 2016 witnessed no such active spell of monsoon and the passage of EW was confined to the eastern part of Bay of Bengal and never entered into the Indian peninsula.
ISSN:2347-4327
0253-4126
0973-774X
DOI:10.1007/s12040-021-01807-8