DOI: 10.5281/zenodo.15507275
title: Modulation of Diurnal SST and Diurnal Warm Layer Variability by Salinity-Driven Stratification in the Bay of Bengal

description: This dataset includes physical properties of the upper ocean collected during field campaigns in the Bay of Bengal in July 2019 and August–September 2015. The data is used for the JPO paper "Modulation of Diurnal SST and Diurnal Warm Layer Variability by Salinity-Driven Stratification in the Bay of Bengal" and are derived from in-situ instrumentation and are organized into the following components:




1. D-BASIS (Drifting Buoy Air-Sea Interaction System)– July 2019



Surface Meteorological Data:Files are named Met_DX.nc, where X = 1 to 3, corresponding to the mooring number.QC details are available at: WHOI UOP Instrumentation

Wirewalker Profiler Data:Files are named WW_DX.nc, where X = 1 to 3.QC details: Zheng et al. (2022), Journal of Atmospheric and Oceanic Technology, DOI link





2. FastCTD Transects – July 2019



Description: Five transects were conducted using a ship-towed FastCTD profiler.

Files: Named TransectX_FastCTD_MISOBOB_2019.nc, where X = 1 to 5.

Details: Transect coordinates and durations are described in the associated publication.





3. Drifter Deployments



2015:File: drifter_ASIRI_2015.ncNumber of drifters: 45QC references: Hormann et al. (2016); Essink et al. (2019)

2019:File: drifter_MISOBOB_2019.ncNumber of drifters: 28QC procedure: Outliers removed using a 3-standard deviation threshold in a 2-hour rolling window





Data Structure and Format

All datasets are provided as NetCDF (.nc) files. Each file includes the variables along with their units. Please refer to the metadata within each file for detailed variable descriptions and attribute information.

 
description: Diurnal cycles of Sea Surface Temperature (SST) are important for ocean–atmosphere coupling. However, observations of their lateral variability, especially in freshwater-dominated regions and in presence of Diurnal Warm Layers (DWLs), remain limited. This study investigates the spatial differences in the diurnal SST amplitude (during DWL and non-DWL days) and subsurface DWL evolution in the Bay of Bengal using remote sensing, in-situ observations, and 1-D modeling. While satellite data reveal O(1 C) differences in diurnal SST amplitude over 100 km, in-situ observations uncover finer-scale and more extreme variability, especially during DWL events. We observe that gradients in diurnal SST amplitude over mesoscale and smaller lengths (< 100 km) are larger during DWL days (median: 0.2 C, extreme: 1.4 C) when compared to non-DWL days (median: 0.1 C, extreme: 0.2 C). Observations from drifters and complementary 1-D model simulations reveal that lateral differences in salinity-driven stratification leads to diurnal SST amplitude differences of about 0.2 C for shallow mixed layer scenarios (< 8 m). While stratification differences explain the median variability in diurnal SST amplitude, extreme differences in diurnal SST require additional contributions from spatial variations in surface forcing and optical properties. Observations also reveal that lateral differences in salinity stratification modify the DWL response, leading to O(10 m) differences in DWL depth, making it the same order as typical MLD scales in the Bay. These results highlight the critical role of small-scale differences in salinity-driven stratification (set by rainfall and mesoscale flow fields in the Bay) in causing diurnal SST and DWL response differences.