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Evolution mechanism of contrasting phases of consecutive IOD events from 1994 to 1998

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Title Evolution mechanism of contrasting phases of consecutive IOD events from 1994 to 1998
 
Creator Anil, N
M R, Ramesh Kumar
Sajeev, R
Saji, P K
 
Subject Ekman transport
El-Nino
Indian Ocean
Indian Ocean Dipole
La-Nina
Monsoon
 
Description 521-532
The Dipole Mode Index (DMI), an Index used to represent the Indian Ocean Dipole (IOD), shows a back to back occurrence of positive and negative IOD events during the period 1994 to 1998. The year 1994 was a strong positive IOD year and was followed by a strong negative IOD in 1996. The positive IOD in 1997 and negative IOD in 1998 were co-occurred with the strong El-Nino and strong La-Nina, respectively. In the present study, we have looked into the evolution of consecutive IOD events during the period 1994 to 1998 and analyzed the differences in their formation, features and association with Indian Summer Monsoon Rainfall (ISMR) for various homogenous regions of the Indian subcontinent. We have found that the El-Nino and La-Nina enhances the IOD-induced positive SST anomalies in the western and eastern parts of the Indian Ocean during the co-occurred years, respectively. The evolution of positive IOD in 1997 is driven by the strong easterly wind anomalies associated with strong El-Nino. The positive anomalies of SST in the western equatorial Indian Ocean is maintained by the El-Nino which results in the long life span of positive IOD in the year 1997 than that of pure positive IOD year 1994. The westward propagating Rossby wave generated due to PIOD is maintained by strong El-Nino in the year 1997. The vertical dynamics, represented by D20, showed minor differences during the pure and co-occurred IOD events. The positive IOD years with El-Nino had good correlation with the Peninsular India and Central North East India regions rainfall. Since we have used only limited samples or cases under the different categories, our present results are preliminary in nature.
 
Date 2021-08-24T06:37:45Z
2021-08-24T06:37:45Z
2021-07
 
Type Article
 
Identifier 2582-6727 (Online); 2582-6506 (Print)
http://nopr.niscair.res.in/handle/123456789/57954
 
Language en
 
Publisher NIScPR-CSIR, India
 
Source IJMS Vol.50(07) [July 2021]