WOA23 B5C2 Sound Velocity Datasets (Annual, Seasonal and Monthly) 1/4 degree resolution

This dataset contains derived climatological seawater sound-speed fields based on the World Ocean Atlas 2023 (WOA23), NOAA NCEI’s objectively analysed oceanographic climatology constructed from World Ocean Database 2023 observations. Period code B5C2 represents 2015–2022, an eight-year reference interval distinct from the longer-term WOA23 decav product. Resolution code 04 denotes a 0.25° latitude × 0.25° longitude grid, equivalent to 15 angular minutes, rather than one-quarter of an angular minute. Temporal identifiers distinguish annual climatology (00); monthly climatologies (01 January, 02 February, 03 March, 04 April, 05 May, 06 June, 07 July, 08 August, 09 September, 10 October, 11 November and 12 December); and seasonal climatologies (13 January–March, 14 April–June, 15 July–September and 16 October–December). These seasonal intervals correspond to Northern Hemisphere winter, spring, summer and autumn. Annual and seasonal temperature and salinity source products provide 102 standard depth levels covering 0–5500 m, while monthly products provide 57 levels covering 0–1500 m. The nominal depth coordinates do not guarantee valid values throughout every profile; source masking accounts for land and the ocean bottom. Sound-speed fields for the WOA23 B5C2 , resolution 04 collection were derived using the Python CalculateSvp class from the objectively analysed temperature ( t_an ) and salinity ( s_an ) fields at the selected source grid cells and standard depths. Two separate estimates are produced: v_an_chen , calculated using the implemented Chen–Millero/UNESCO-type temperature–salinity–pressure polynomial, and v_an_leroy, calculated using the Leroy, Robinson and Goldsmith (2008) temperature–salinity–depth–latitude equation; both yield sound speed in metres per second. For the former, pressure is estimated from depth and latitude using Leroy and Parthiot (1998), with an optional configured regional correction, and converted from MPa to bar before evaluation. The class applies these calculations directly to the climatological inputs without additional spatial or vertical interpolation, extrapolation or missing-value filling. The results are derived climatological sound-speed estimates rather than direct acoustic measurements. The files in this dataset are used with these MB-System tools: mbsvpbest, mbsvproute, mbsvplocation, and mbsvpnearest. They are available here: https://github.com/dwcaress/MB-System References: https://www.ncei.noaa.gov/sites/default/files/2022-06/woa18documentation.pdf https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/ https://www.ncei.noaa.gov/access/world-ocean-atlas-2023/