The Dynamics of Rice Cropping Calendar and Its Relation with the ENSO (El Niño-Southern Oscillation) and IOD (Indian Ocean Dipole) in Monsoon and Equatorial Regions of Indonesia

Abstract

The relative impacts of the El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events of Rice Cropping Calendar on Equatorial and Monsoon Region of Indonesia were studied. The spatial distribution of partial correlations between rainfalls with the ENSO and IOD over West Sumatera and West Java indicated a significant impact on rainfall anomalies normally along the period of September – November. The ENSO and IOD events, which is known as a monsoon type, had a wider impact in West Java, especially over northern of West Java. On the other hand, there was only a little impact of the ENSO and IOD on rainfall anomalies in the southern-west of West Sumatera. This strength was shown to be associated with the evolution of distinct weather types revealed by Pearson analysis. In these regions, the same impact of the ENSO and IOD on the width of planting area was very weak in the period of December-March whereas that in the period of June-November the impact on West Sumatera reached only 10% moreover, the impact in West Java could reach up to 80%. On the period scales, the ENSO and IOD events had significant impacts to delayed onsets of rice cropping calendar in which they were more intense than previous ones. In general, the magnitude of ENSO-delayed onsets was greater than delays to the IOD. The period-stratified ENSO variability during each of the months from September to November had a significant impact of delayed planting 2 to 4 dekads in West Sumatera and 4 to 6 dekads on West Java. This confirmed that strong ENSO events indeed affected the southern of West Sumatera and northern of West Java. Meanwhile, the period-stratified IOD variability on West Sumatera and West Java had a significant impact of delayed planting 2 to 4 dekads.