In situ physical and biogeochemical observation for southeastern waters off Sri Lanka island

The field observations were conducted aboard the R/V Xiangyanghong 06 from January 5 to 15, 2020, in the southeastern off Sri Lanka, covering a total of 18 stations (from S1 to S18). Field observations were performed using an integrated biochemical sensor system equipped with a Seabird 25 plus CTD, an in-situ ultraviolet nitrate sensor (Seabird Deep-SUNA), an in-situ fluorescence sensor, and an underwater vision profiler (UVP 5HD) enabling high-resolution of temperature, salinity, depth, nitrate concentration, Chl-a, and particle size distribution. To ensure data reliability, the Deep-SUNA and fluorescence sensors were thoroughly calibrated before the cruise. Water samples were also collected and analyzed in the laboratory using an AA3 segmented flow analyzer and fluorometric method to validate nitrate and Chl-a concentrations, respectively. During the observations, the integrated biochemical sensor systems was deployed at a constant speed of approximately 0.5 m s-1. Detailed descriptions of key data processing methods are provided in the supplementary materials, including the estimation of vertical mixing intensity using the Thorpe scale method (Park et al., 2014; Thorpe, 1977), estimation of POC flux based on UVP observations (Guidi et al., 2008; R. Kiko et al., 2017), and the definition of the barrier layer (de Boyer Montégut et al., 2004). File Structure We have provided four .xls files, each containing specific datasets: 1) physical and biochemical parameters: Depth, temperature, salinity, nitrate, Chl-a at every meter depth interval, ranging from 2–250 m. 2) Nitrate diffusion flux: Nitrate diffusion flux data at 5-meter depth intervals, ranging from 10–250 m. 3) particle abundance Particle concentration, at every meter depth interval, ranging from 10–150 m 4) particulate carbon flux particulate carbon flux, at 5-meter depth interval, ranging from 10-500 m