The Arabian Sea (AS) and the Bay of Bengal (BoB) form an integral part of the northern Indian Ocean, exhibiting distinct characteristics despite being in the same latitudinal region. The present study is aimed at assessing the surface and sub-surface chlorophyll-a (chl-a) structure of the AS and the BoB utilizing concurrent Biogeochemical-Argo measurements. As the calibration coefficients require post-processing evaluation to suit the regional waters, where the floats are deployed, two floats each in the AS (WMO ID: 2902093 & 2902118) and the BoB (WMO ID: 2902086 and 2902114) falling in the same latitudinal belt are chosen on a pilot basis for correcting the gain and offset of the derived chl-a. The chl-a derived using scale factor and dark counts provided by the manufacturer is further calibrated using satellite measured chlorophyll and modified chl-a values are obtained. The modified chl-a data obtained by applying the gain and offset was then used to study the variability of chlorophyll, deep chlorophyll maximum (DCM) and factors responsible for its variability in both basins. The present study upheld the existence of a permanent DCM in both the basins. Similarly, the relationship between DCM and mixed layer depth (MLD) is assessed and the DCM is found to vary at an annual mode in BoB and at a quasi-semi annual mode in the AS region. Strong correlation between DCM and depth of 26 °C isotherm was also observed in both AS and BoB and the rationale behind it was analyzed. Existence of sub-surface blooms in the pre-monsoon season in the upper 200 m of the AS region is observed. The time-series data from BGC-Argo floats revealed the bio-optical mechanisms and their relationship with the physical processes.

阿拉伯海（AS）和孟加拉湾（BoB）构成了北印度洋的组成部分，尽管处在同一纬度地区，但仍具有鲜明的特征。本研究的目的是评估在表面和次表面叶绿素一个（chl-一个AS和利用并发生物地球化学-Argo的测量摆锤的）结构。由于需要对校准系数进行后处理评估，以适应浮标部署所在的区域水域，因此AS中的两个浮标（WMO ID：2902093＆2902118）和BoB（WMO ID：2902086和2902114）都位于同一位置在飞行员的基础上选择纬度带，以校正导出的chl-a的增益和偏移。该chl-一利用卫星提供的叶绿素，可以进一步校准使用比例因子和制造商提供的暗计数得出的校准值，并获得修改后的chl- a值。然后，通过应用增益和偏移量获得的经修改的chl- a数据用于研究两个盆地中叶绿素，深叶绿素最大值（DCM）的变异性及其造成其变异性的因素。本研究支持在两个盆地中均存在永久性DCM。同样，评估DCM和混合层深度（MLD）之间的关系，发现DCM在BoB中以年模式变化，而在AS地区以准半年模式变化。在AS和BoB中也观察到DCM与26°C等温线深度之间的强烈相关性，并分析了其背后的原理。观察到在AS区上部200 m的季风前季节存在地下水华。来自BGC-Argo浮子的时间序列数据揭示了生物光学机制及其与物理过程的关系。