SimpleEddyDetection

Simple Oceanic Mesoscale Eddy Detection based on sea level anomaly (sla)

Note:

• This function is provided "as is" without warranty of any kind.
• One should be careful if using it in scientific research as its eddy identification approach is quite simple.

Dependency:

Matlab toolbox "M_Map" is required.

Inputs:

lon: longitude, vector or matrix generated by "meshgrid" with range between [-180,180]

lat: latitude, vector or matrix generated by "meshgrid" with range between [-90,90]

sla: (spatial high-pass filtered) sea level anomaly (unit: meter) falls within the area defined by viarable "lon" and "lat". Continent or no value at grid point is masked with "NaN".

upperFolderName: a string to signify the upper folder name or path.

whichYear: The year of data "sla". Only an integer is accepted.

whichMonth: The month of data "sla". Only an integer is accepted.

whichDay: The day of data "sla". Only an integer is accepted. Can be replaced by "[]".

whichHour: The hour of data "sla". Only an integer is accepted. Can be replaced by "[]".

amplitudeThreshold (optional): unit: cm. Default is 3 cm. Note: this is an artificial threshold that an detected eddy is required to meet this criterion.

radiusThreshold (optional): unit: Km. Default is 45 Km, designed for altimetry data due to its resolving capability. Note: this is an artificial threshold that an detected eddy is required to meet this criterion.

Outputs:

Eddy: a structure array contains the properties of detected eddies:

Eddy.type: polarity of detected eddy. -1 for cyclonic while 1 for anticyclonic.

Eddy.center: longitude and latitude of eddy centroid.

Eddy.amplitude: longitude and latitude of eddy's sla extreme as well as eddy's amplitude (set to positive no matter if it is cyclonic or anticyclonic. Unit: cm)

Eddy.radius: radius of an circle that has the same area as the eddy area enclosed by the eddy edge. Unit: Km

Eddy.edge: two vectors specify the longitudes and latitudes of eddy edge defined by the outermost closed sla contour.

A NetCDF file will be generated if successful detection.

Cited by

• Feng Jiang et al., Glider Network Observation Unraveling A Cyclonic Eddy in the Northwestern Pacific Subtropical Countercurrent. 2023 J. Phys.: Conf. Ser. 2486 012009. doi:10.1088/1742-6596/2486/1/012009
• Robertson, R. Tidal and internal tidal impacts in the Tasman Sea. Geosci. Lett. 10, 8 (2023). https://doi.org/10.1186/s40562-023-00262-1
• Bodren, C., Iglesias, I., Amorim, F., and Lázaro, C., “Evaluating Spatio-Temporal Variability in Sea Level and Eddies in the Azores Region”, in <i>2023 Ocean Surface Topography Science Team Meeting</i>, 2023, Art. no. 66. doi:10.24400/527896/a03-2023.3749.
• Jebri, F., Srokosz, M., Raitsos, D.E. et al. Absence of the Great Whirl giant ocean vortex abates productivity in the Somali upwelling region. Commun Earth Environ 5, 20 (2024). https://doi.org/10.1038/s43247-023-01183-9
• John A Gittings, Giorgio Dall’Olmo, Weiyi Tang, Joan Llort, Fatma Jebri, Eleni Livanou, Francesco Nencioli, Sofia Darmaraki, Iason Theodorou, Robert J W Brewin, Meric Srokosz, Nicolas Cassar, Dionysios E Raitsos, An exceptional phytoplankton bloom in the southeast Madagascar Sea driven by African dust deposition, PNAS Nexus, Volume 3, Issue 10, October 2024, pgae386, https://doi.org/10.1093/pnasnexus/pgae386

Author:

Dr. Chi Xu (SCSIO, CAS)

SEP 07 2020

https://data.scsio.ac.cn/characteristic/zhongchiduwo