Global map of the total semidiurnal internal tide variance at 1,000 dbar from Argo data

Gaspard Geoffroy

This dataset is a global map, on a regular 2.5° × 2.5° grid, of the total semidiurnal internal tide variance at 1,000 dbar. It is computed from in situ temperature and pressure time series recorded during the park phase of Argo floats.

The total semidiurnal internal tide variance is not affected by phase decorrelation but only by mixing, scattering, and nonlinear processes. The geographical distribution of the total variance can therefore be used to better understand these decay processes.

The original Argo data used to produce this dataset are scattered at the global scale and span the period 2004 – ⁠2024. The final gridded product is obtained by complex demodulation of local mean autocovariance series of the isotherms vertical displacement at 1,000 dbar.

Citation

Gaspard Geoffroy (2024) Global map of the total semidiurnal internal tide variance at 1,000 dbar from Argo data. Dataset version 2. Bolin Centre Database. https://doi.org/10.17043/geoffroy-2022-argoit-2

References

Argo (2000) Argo float data and metadata from Global Data Assembly Centre (Argo GDAC). SEANOE. https://doi.org/10.17882/42182

Geoffroy, G., & Nycander, J. (2022). Global mapping of the nonstationary semidiurnal internal tide using Argo data. Journal of Geophysical Research. Oceans, 127(4). https://doi.org/10.1029/2021jc018283

Geoffroy G (2024) Scripts for mapping the total semidiurnal internal tide variance at 1,000 dbar using Argo data. Software version 2.0.0. Bolin Centre Code Repository. https://doi.org/10.57669/geoffroy-2022-argoit-2.0.0

Data description

This dataset is composed of a unique netCDF file. It takes the form of a regular 2.5° × 2.5° gridded map where each pixel corresponds to a circular geographical patch of radius 200 km. For each pixel (corresponding to a lat, lon position), the variable n_segs stores the number of 32-day segments of Argo data used to compute the local mean autocovariances of the isotherms vertical displacement. The local mean autocovariance (a function of time lag tau) and associated standard error are stored in the variables muacov_eta and semacov_eta, respectively. The total semidiurnal internal tide variance is obtained by complex demodulation of the local mean autocovariance. It is stored along with its standard deviation in the variables SD_demod_eta and SD_demod_eta_std, respectively.

Comments

This dataset was produced by using the Scripts for mapping the total semidiurnal internal tide variance at 1,000 dbar using Argo data by Geoffroy (2024). It is based on in situ observations recorded during the park phase of Argo floats (Argo 2000). These data were collected and made freely available by the International Argo Program and the national programs that contribute to it. The Argo Program is part of the Global Ocean Observing System.

The processing of the Argo data to produce the global map of the total semidiurnal internal tide variance is described by Geoffroy and Nycander (2022). Please cite the latter article when using this dataset and contact the corresponding author Gaspard Geoffroy for any scientific or data-related questions.

Version history

Version 2

• Based on the Argo data from the Coriolis/Ifremer/France GDAC instead of the U.S. GDAC.
• Updated processing of the Argo data.

Version 1

• Initial release.