Abstract
Abstract. Ocean surface phytoplankton responses to the tropical cyclone (TC)/storms have been extensively studied using satellite observations by aggregating the data into a weekly or bi-weekly composite. The reason behind is the significant limitations found in the satellite-based observation is the missing of valid data due to cloud cover, especially at the time of cyclone track passage. The data loss during the cyclone is found to be a significant barrier to efficiently investigate the response of chl-a and SST during cyclone track passage. Therefore it is necessary to rectify the above limitation to effectively study the impact of TC on the chlorophyll-a concentration (chl-a) and the sea surface temperature (SST) to achieve a complete understanding of their response to the TC prevailed in the Arabian Sea. Intending to resolve the limitation mentioned above, this study aims to reconstruct the MODIS-Aqua chl-a, and SST data using Data Interpolating Empirical Orthogonal Function (DINEOF) for all the 31 cyclonic events occurred in the Arabian Sea during 2003-2018 (16 years). Reconstructed satellite retrieved data covering all the cyclonic events were further used to investigate the chl-a and SST dynamics during TC. From the results, the exciting fact has been identified that only two TC over the eastern-AS were able to induce phytoplankton bloom. On investigating this scenario using sea surface temperature, it was disclosed that the availability of nutrients decides the suitable condition for the phytoplankton to proliferate in the surface ocean. Relevant to the precedent criterion, the results witnessed that the 2 TC (Phyan and Ockhi cyclone) prevailed in the eastern AS invoked a suitable condition for phytoplankton bloom. Other TC found to be less provocative either due to less intensity, origination region or the unsuitable condition. Thereby, gap-free reconstructed daily satellite-derived data efficiently investigates the response of bio-geophysical parameters during cyclonic events. Moreover, this study sensitised that though several TC strikes the AS, only two could impact phytoplankton productivity and SST found to highly consistent with the chl-a variability during the cyclone passage.
Highlights
The unusual physical dynamics such as tropical cyclone (TC) triggers the biogeochemical properties present in the ocean, which disturbs the distribution and dynamics of phytoplankton (Lin, 2012; Wang & Zhao, 2008)
The reconstruction of chl-a data obtained from MODIS-Aqua chl-a products that cover the cyclonic events in the Arabian Sea is achieved using Data Interpolating Empirical Orthogonal Function (DINEOF) method
On comparing the images before and after the reconstruction, it is found that the DINEOF method could fill missing data that covers the cyclone passage efficiently even though the data loss is high
Summary
The unusual physical dynamics such as tropical cyclone (TC) triggers the biogeochemical properties present in the ocean, which disturbs the distribution and dynamics of phytoplankton (Lin, 2012; Wang & Zhao, 2008). Most importantly during TC, the ocean faces fluctuation in the physical properties like cooling of sea surface temperature (SST) caused by vertical mixing of the water column (i.e. upwelling) (Lin 2012; Subrahmanyam et al, 2002). Such episodic events could bring more deep-seated nutrients to the upper surface that might induce the favourable conditions for certain phytoplankton types (Subrahmanyam et al, 2002).
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