THE EFFECT OF ENSO ON RAINFALL AND CHLOROPHYLL-A VARIABILITY IN THE WATERS OF PULAU LAUT

Abstract

The waters of Pulau Laut have considerable marine and marine resource potential. The waters of the Pulau Laut cluster have been studied for the feasibility of mariculture (cage farming, floating nets) based on oceanographic and water chemistry parameters. Coastal areas and small islands such as Pulau Laut are also seen as potential locations for marine ecotourism development. This study aims to analyze the influence of the El Niño Southern Oscillation (ENSO) phenomenon on rainfall variability and chlorophyll-a concentration in the Pulau Laut waters. This study is relatively new, considering that there are not many previous studies that specifically discuss the relationship between ENSO, rainfall, and chlorophyll-a in this area. This study uses satellite-based observation data. The rainfall and chlorophyll analyzed cover a 16-year period, from 2007 to 2022. The rainfall data was taken from the Global Satellite Measurement of Precipitation (GSMaP) available through JAXA Global Rainfall Watch with a spatial resolution of 0.10°. Chlorophyll-a concentration data were obtained from the Ocean Color CCI (OC-CCI) Level 3 Standard (L3S) product provided by Marine Copernicus. The research method refers to a quantitative approach as described by, where numerical data are statistically analyzed and displayed through graphs and maps as a form of visualization. All temperature, wind, chlorophyll, and rainfall data are processed spatially using IDL (Interactive Data Language) software. Analysis of the relationship between ENSO and rainfall and chlorophyll-a in the waters of Pulau Laut shows that in the west season there is no significant relationship between ENSO and rainfall, indicated by a p-value of 0.595 (>0.05) with a correlation of -0.079, reflecting a very weak negative relationship. In the east season, the relationship becomes significant, with a p-value of 0.008 and a correlation of -0.378, indicating that the stronger El-Nino, the rainfall tends to decrease. In the west season, there is a significant relationship with a p-value of 0.000 (<0.05) and a correlation of -0.525. This indicates that during the west monsoon, an increase in ENSO (leading to El Niño) is associated with a decrease in chlorophyll-a concentration with a moderate relationship strength. ENSO does not significantly affect rainfall on Laut Island during the west monsoon, but it does significantly affect rainfall during the east monsoon because rainfall decreases when El Niño strengthens. Chlorophyll-a during ENSO actually shows a significant effect during the west monsoon, where its concentration decreases when El Niño increases, while in other seasons the effect is inconsistent.