Influence of El Niño–Southern Oscillation (ENSO)

 

Krishnamurthy and Goswami (2000) showed that that monsoon rainfall decreases (increases) during warm (cold) ENSO year by comparing observed monsoon rainfall and various ENSO indices

 

Various ENSO indices

Indian Ocean (IO) index : Sea surface temperature (SST) anomaly averaged over 50–100 degree E, 20 degree S–20 degree N)

Pacific cold tongue (CT) index : SST anomaly averaged over 180–90 degree W, 10 degree S-10 degree N)

North Pacific SST (NP) index : SST anomaly averaged over 150 degree E–150 degree W, 20–45 degree N)

Southern Oscillation (SOI) index : The area-averaged SLP anomaly difference between the tropical Pacific from the dateline eastward and the reminder of the tropical oceans (Atlantic, Indian, and western Pacific) in the 20 degree S–20 degree N belt

 

Correlation between standard deviation of each ENSO indices with Indian monsoon rainfall for 1876-1986. significant correlations at 99% and 99.9% are indicated by one and two asterisks, respectively
Correlation coefficient
Indian monsoon rainfall
IMR
1
 
Niño-3
-0.59**
CT
-0.58**
NP
0.23
IO
-0.07
SOI
0.62**

 

Interannual variation of most of the ENSO indices are negatively correlated with Indian summer monsoon