The Relative Influences of ENSO Conventional, ENSO Modoki and Indian Ocean Dipole on Mindanao and Northeastern Borneo Precipitation Anomaly

Abstract:

Since the discovery of El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and El Nino Modoki (EM), many had thought that all of these 3 climate phenomena are influencing the precipitation in Mindanao and Northeastern Borneo. However, no study was done to identify the real impact of these three climate phenomena on the precipitation of this area. Based on the situation above, this study intends to investigate the influence of ENSO, IOD and EM to Mindanao and Northeastern Borneo precipitation. Besides that, we are investigating factor other than those dominant climate phenomena that affect the precipitation in the study region.

For this study, we used APHRODITE (observation precipitation data) as our primary precipitation data. For analysis, we used 850hPa wind data (JRA-55), 200hPa stream function data (JRA-55) and sea surface temperature data (SST; HadISST) from 1961 to 2007. Correlation, partial correlation and composite analyses are used as the method for this study.

We discovered that ENSO during December-February (DJF), March-May and September-November (SON) influence the precipitation in the study region. Further analysis indicated that EM during DJF and SON influences precipitation of those regions. The results show that the ENSO and the EM influence the precipitation of this region through Walker circulation and associated teleconnections. However, IOD influence is not significant in any season.

It is also discovered that the precipitation in the region is greatly affected by the local winds northeast of Mindanao during DJF. Those are the regional monsoon winds for the Asian Winter Monsoon. In addition, the winter monsoon rainfall is influenced by the winds that are in turn associated with the variations in Aleutian Low and Siberian High. Further analysis will be done to understand the links among them (SST, regional monsoon winds and 200hPa streamfunction) and consequently the mid-latitude teleconnections that affect the regional monsoon winds.