IMPACT OF 2016 WEAK LA NIÑA MODOKI EVENT OVER THE INDONESIAN REGION

Abstract

After an extreme 2015/16 El Niño phenomenon, the Pacific Ocean witnessed a La Niña Modoki
event, while a strong negative IOD simultaneously took place in the Indian Ocean. The event was weaker in
intensity and shorter in time, compared to the similar case in 1998/99. Using the combined monthly sea surface
temperature (SST) derived from the Optimum Interpolation Sea Surface Temperature (OISST) version 2, the
atmospheric reanalysis data from the National Center for Environmental Prediction and the National Center
for Atmospheric Research (NCEP/NCAR) and the precipitation data from the Tropical Rainfall Measuring
Mission (TRMM), the dynamics and possible impact of this event were investigated. The 2016 La Niña Modoki
initially developed in boreal summer, subsequently matured in autumn, and abruptly terminated in winter. This
short-lived La Niña Modoki was associated with a unique SST anomalies pattern in the Indo-Pacific region.
Strengthened easterly winds in the central tropical Pacific Ocean was associated with a warming SST over the
western Pacific Ocean and triggered convergence in the lower atmosphere causing upward motion and
enhanced convective process over the Indonesian region. As a consequent, most of the Indonesian region
experienced excess precipitation during boreal summer, except in the northern part of the Sumatra Island.