A chlorophyll-a front is a border between two water masses with chlorophyll-a concentration gradient 0.15-0.5 mg/m3. Such masses and the related interface are usually located near the northern, western and southern coastal parts of the Javal Sea (between 3º S – 5º S and 110º E – 116 º E, 3º S – 5º30’ S and 106º E – 107º E, 5º S – 7º30’ S and 116º E – 114º E), and are strongly influenced by the northwest monsoonal winds system. In this work, we used the Single Image Edge Detection (SIED) Algorithm to detected the frontal face. The gradient level we used to designate the passing from and into a front was 0.5 mg/m3. Monthly data of the chlorophyll-a image, sea surface current imagery and rainfall levels from January to December 2015 were used in this study. From this data, we discovered that the monthly average of the lengths of the chlorophyll-a front ocurrence reaches a greatest extent in March with 2513.64 km and a least extent at 510.25 km in October. In addition, the fronts move closer to the coastal area during the transitional I to transitional II period. Our data suggest that surface current affects frontal movement. Moreover, the number of succeeding fronts and the intensity of change are influenced by nutrient supply from rivers that is, in turn, affected by rainfall level. This is because the rainfall data shows a similar pattern with temporal front data.
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