Peristiwa El Nino dan Pengaruh IOD Terhadap Hujan di Malaysia (El Nino Events and the Influence of IOD on Rainfall in Malaysia)

Abstract

Kewujudan Lautan Pasifik di timur Malaysia dan Lautan Hindi di baratnya mempengaruhi jumlah hujan di Malaysia. Antara kesan lautan ini adalah fenomena El Nino (La Nina) yang lazimnya menyebabkan keadaan kering (basah) di Malaysia. Hubungan hujan dan pengaruh lautan ini dikaji melalui indeks lautan serta jumlah hujan yang diterima di Malaysia dari tahun 1970 hingga 2008 di 12 stesen kajiiklim utama menggunakan statistik seperti analisis korelasi dan multivariat. Indeks untuk isyarat peristiwa El Nino di Lautan Pasifik adalah Equatorial Southern Oscillation Index (EQSOI), Oceanic Nino Index (ONI) dan Southern Oscillation Index (SOI) manakala isyarat untuk kejadian Indian Ocean Dipole (IOD) di Lautan Hindi menggunakan Dipole Modes Index (DMI). Objektif kajian ini adalah untuk mengkaji apakah pengaruh IOD sewaktu El Nino dan La Nina terhadap hujan di Malaysia. Hasil kajian mendapati hubungan antara min SOI/ONI/EQSOI/DMI dan jumlah taburan hujan adalah positif/negatif/negatif/negatif tapi lemah. IOD mempunyai pengaruh yang kadangkala positif dan negatif terhadap taburan hujan. Pola hujan tahunan di Semenanjung kurang dipengaruhi oleh El Nino berbanding di Malaysia Timur kerana kehadiran Lautan Hindi. Walaubagaimanapun ujian ANOVA tidak menunjukkan hubungan yang signifikan antara anomali hujan dan indeks lautan. Kejadian El Nino dan fasa IOD positif yang berlaku sebanyak 12% menyebabkan keadaan kering yang hujannya kurang daripada normal sementara 12% daripada kejadian La Nina sewaktu fasa IOD negatif menyebabkan berlakunya lebih banyak hujan daripada normal. Kajian ini menunjukkan betapa pentingnya pemantauan terhadap indeks lautan di Lautan Pasifik dan Lautan Hindi dalam menentukan perancangan sumber air di negara ini terutama dalam keadaan perubahan iklim yang mendatang.

Kata Kunci: El Nino, Lautan Hindi, Indian Ocean Dipole, Lautan Pasifik, Malaysia

El Nino Events and the Influence of IOD on Rainfall in Malaysia

ABSTRACT

The existence of the Pacific Ocean to the east of Malaysia and the Indian Ocean to its west influences the amount of rainfall in Malaysia. One of the effects of these oceans is the occurrence of the El Nino (La Nina) phenomenon that often causes dry (wet) condition in Malaysia. The oceanic indices and amount of rainfall received in Malaysia from 1970 to 2008 at 12 major climate stations forms a basis for the investigation on the oceanic influence by using statistical methods such as correlation and multivariate analyses. The Equatorial Southern Oscillation Index (EQSOI), the Oceanic Northern Oscillation Index (ONI) and the Southern Oscillation Index (SOI) represented the El Nino phenomenon in the Pacific Ocean while the signal for the Indian Ocean Dipole (IOD) uses the Dipole Modes Index (DMI). The objective of this study is to investigate the influence of IOD during El Nino and La Nina on the rainfall in Malaysia. The results showed that the relationship between SOI/ONI/EQSOI/IOD and the amount of rainfall was positive/negative/negative/negative but weak. The IOD has a positive and negative influence on the rain. Rainfall patterns indicated that the El Nino affected less the amount of rainfall in the Peninsula compared to Sabah and Sarawak due to the presence of the Indian Ocean. The ANOVA test showed no significant relationship existed between the rainfall anomalies and the ocean indices. The 12% occurrences of El Nino and the positive IOD phase resulted in drier than normal conditions while 12% of the La Nina incidences during the negative IOD phase produced more rainfall than normal. This study shows the importance of monitoring the oceanic indices in the Pacific and Indian Oceans in determining future water resources planning for our country especially for the upcoming climate change.

Keywords: El Nino, Indian Ocean, Indian Ocean Dipole, Pacific Ocean, Malaysia