Code and datasets for: Asymmetric Basin-Wide Responses of Coastal Phytoplankton Biomass to the Indian Ocean Dipole

This repository contains the data and MATLAB codes used to reproduce the main results of the manuscript “Asymmetric Basin-Wide Responses of Coastal Phytoplankton Biomass to the Indian Ocean Dipole.”

The archive is organized into four components: 

01. Code, containing six MATLAB scripts corresponding to Figures 1–5 and 7; 

02. Dataset , containing observational and processed datasets used directly for figure generation; 

03. Auxiliary, containing supporting files such as Kelvin-wave propagation pathways, climate indices, bathymetric sections, land masks, and other ancillary data; 

04. External_Data, which is reserved for publicly available satellite, model, reanalysis, and bathymetric products that can be downloaded from their original repositories;

05. Source Data, generating the figures.

The six figure scripts reproduce: 

(1) satellite-observed climatological and IOD-related coastal chlorophyll-a variability across the eastern Indian Ocean;

(2) NEMO-PISCES-derived chlorophyll-a variability and hydrographic structure along the Kelvin-wave propagation pathway;

(3) interannual differences in hydrographic, biogeochemical, and turbulent-mixing conditions in the Preparis Channel;

(4) time–distance evolution of chlorophyll-a, sea-level, thermocline-depth, equatorial-wind, and local Ekman-pumping anomalies associated with Kelvin-wave propagation;

(5) cross-channel sections of potential temperature, nitrate, chlorophyll-a, turbulent dissipation, diapycnal diffusivity, and nitrate diffusive flux; and

(6) long-term variations in the Dipole Mode Index, Niño 3.4 index, and coastal chlorophyll-a integral during different IOD and ENSO phases.

The field-observation component provides the hydrographic, biogeochemical, and turbulent-mixing measurements used to characterize the vertical and cross-channel structure of the Preparis Channel and to evaluate interannual environmental differences. These observations form the in situ basis for Figures 3 and 5 and complement the satellite, model, and reanalysis analyses used to examine the basin-scale and Kelvin-wave-related responses.

Publicly available external products required by the scripts include Copernicus Marine satellite chlorophyll-a, NEMO-PISCES biogeochemical outputs, GLORYS12 physical reanalysis, sea-level anomaly products, ERA5 winds, and SRTM15+ bathymetry. Product identifiers, DOIs, required MATLAB toolboxes/functions, and input-file information are documented within the corresponding scripts. The repository therefore provides both the in situ observational basis and the data-processing and visualization workflows necessary to reproduce the principal figures and analyses reported in the manuscript.