Chlorophyll-A variability in the southern coast of Java Island, Indian Ocean: corresponding to the tropical cyclone of Ernie

Tropical cyclone is an atmospheric phenomenon formed above warm ocean in a tropical region. Generally, tropical cyclone gives negative impact, such as extreme rainfall, strong winds, and extreme wave height. On the other hand, however, tropical cyclone gives positive impact on triggering the ocean fertility by induced chlorophyll-a concentration caused by vertical mixing and upwelling in the ocean. Related to this, a study has been conducted to determine the concentration of chlorophyll-a after the occurrence of Ernie cyclone in Indian ocean near western part of Australia and along the southern coast of Java island. The data that used in this study is daily wind speed data from 5 - 11 April 2017, daily average data of SST from 5 - 11 April 2017, and 8-day composite data of chlorophyll-a data from Aqua-MODIS satellite. The analysis of chlorophyll-a concentration showed a slow response of ocean fertility increment in the southern coast of Java island. Chlorophyll-a concentration along the cylone trajectory prior to the cyclone was in the range of 0.08 mg/m3 – 0.15 mg/m3 and significantly increased up to 88%–100% in a week after the occurrence of cyclone. On the next third and fourth weeks after cyclone, the concentration of chlorophyll-a along the cyclone trajectory decreases gradually. Meanwhile its sea surface temperature decreased significantly, especially in areas where cyclone had passed.