Figure 7 – El Nino Modoki and La Nina Modoki

La Nina Modoki is associated with low sea surface temperature (SST) in central tropical Pacific Ocean while eastern and western tropical pacific are warm relatively. It produces two walker cells with rising limbs at both ends of tropical pacific and descending limb of both cells fall at central equatorial pacific (figure 7d).

Together El Nino Modoki and La Nina Modoki forms ‘ENSO Modoki’. Several studies have shown that the ENSO Modoki has become more prominent in recent times, as compared to ENSO, and thereby changing the teleconnection pattern arising from the tropical Pacific. The ENSO Modoki has distinct teleconnections and affects many parts of the world. For example, the West Coast of United States of America is wet during El Nino but dry during El Nino Modoki. Recent studies show that teleconnections associated with ENSO Modoki influence the rainfall over India and South Africa.

El Nino results in anomalous two-cell Walker Circulation over the tropical Pacific, with a wet region in the central Pacific. During pre-monsoon and post-monsoon seasons in the North

3 Hadley Cells are the low-latitude overturning circulations that have air rising at the equator and air sinking at roughly 30° latitude.

Indian Ocean, more cyclones form in the Bay of Bengal compared with the Arabian Sea. El Nino is found to suppress cyclone formation in the Arabian Sea. While in some years more cyclones form in the Arabian Sea than usual. This is due to El Nino Modoki. During El Nino Modoki, one of the descending limbs of the walker cell is over the Bay of Bengal which causes dry conditions not conducive for cyclone formation. On the other hand, there is large convergence over the Arabian Sea during an El Nino Modoki explaining the large number of cyclones in that region.