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GlobCurrent Product Data Handbook – The tidal currents 1

GLOBCURRENT

PRODUCT DATA HANDBOOK

THE TIDAL CURRENTS

Customer ESA

Author Consortium

Distribution Consortium and ESA

ESA Contract Number AO/1-7472/13/I-LG

Document Reference Data Handbook

SoW Deliverable Reference D-280

Version/Revision 2.0

Date of issue 11 May 2015

Issued by

(CLS)

Marie-Helene RIO

CLS Project Scientist

Approved by

(NERSC)

Johnny A. Johannessen

NERSC Project Manager

Approved by

(ESA)

Craig Donlon

ESA Technical Officer


Revision Change log

Issue Date Type Change description

1.0 11 Mai 2015 Initial draft

2.0 07 January 2016 RIDS revision Changes to comply with ESA

RIDS


Table of contents

1. Introduction ................................................................................................................................. 4

1.1. The GlobCurrent project ...................................................................................................... 4

1.2. Purpose and scope of this document .................................................................................... 6

1.3. Document structure .............................................................................................................. 6

1.4. Applicable Documents ......................................................................................................... 6

1.5. Reference documents ........................................................................................................... 7

1.5.1. Publications ................................................................................................................... 7

1.5.2. Web sites ....................................................................................................................... 7

1.6. Acronyms and abbreviations ................................................................................................ 7

2. Definition of tidal currents ........................................................................................................ 10

3. Description of the GlobCurrent V1 global tidal currents .......................................................... 10

4. Validation .................................................................................................................................. 10

5. Data Format .............................................................................................................................. 11

6. Summary table of product information ..................................................................................... 17

7. Example read software .............................................................................................................. 17

8. Frequently Asked Questions ..................................................................................................... 18

9. Feedback form .......................................................................................................................... 18

10. Appendix: full CDL dump ...................................................................................................... 18

Table of tables

Table 1:. Overview of satellite sensors, observed quantities, retrieval algorithms and final derived

variables. ......................................................................................................................................... 5

Table 2: General content of a GlobCurrent tidal currentL4 product (L4 CURtid) ....................... 11

Table 3: CDL example description of variable eastward_tidal_current_velocity ........................ 12

Table 4: CDL example description of variable northward_tidal_current_velocity ..................... 13

Table 5: CDL example description of variable eastward_tidal_current_velocity_error .............. 14

Table 6: CDL example description of variable northward_tidal_current_velocity_error ............ 14

Table 7:CDL example description of flags variable ..................................................................... 15

Table 8: CDL example description of quality_level variable ....................................................... 16


1. Introduction

1.1. The GlobCurrent project

Satellite altimetry, arguably the most mature technique for mapping ocean currents, has

permitted breakthroughs in our understanding the dynamics of large-scale (roughly >200-km)

oceanic circulation and an unequalled view of eddy kinetic energy on a global scale. Still, the

conventional coarse ground track spacing of an individual altimeter is known to limit cross-track

resolution to several hundred km. Similarly, multiple altimeters yield gridded maps of sea

surface height (SSH) that is limited to a resolution of about 100 km and 10 days. This so-called

"altimetry gap" has prompted attempts to combine the lower resolution altimeter data with

sequences of medium and higher resolution satellite and in situ observations.

Direct and indirect estimates of ocean surface current and higher level derived quantities such as

frontal boundaries can indeed be derived using a variety of satellite sensors, including altimetry

(both conventional and SAR mode), gravimetry, SAR imaging and Doppler properties,

scatterometry, optical (VIS and TIR) and passive microwaves. Sparse in-situ current

measurements from drifting and moored buoys, coastal HF-radar installations, Argo floats,

gliders and ship observations can also complement these satellite measurements. Each of these

satellite and in-situ based measurement techniques has specific strengths and limitations (e.g.,

resolution, coverage, accuracy, depth integration, cloud dependence, empirical based retrieval

methods, etc). The objective of the GlobCurrent project is to develop and use systematic data

merging and sensor synergy combined with advanced processing tools and simulation models, in

order to optimize the complementary strength of each sensing technique. Deficiencies are

thereby reduced and the final estimate of the OSC is more consistent, regular and reliable. In

turn, the use and uptake of satellite based OSC derived products will grow.

The GlobCurrent Technical Note ([AD-3]) gives an analysis and interpretation framework for the

Ocean Surface Current (OSC) estimated in the GlobCurrent project, primarily using different

satellite observations complemented, when possible, with in situ measurements.

Table 1 shows a synthesis of the retrieval algorithms and tools together with the final retrieved

geosphysical information for each satellite sensor used in the GlobCurrent projet.


Satellite

sensor

Satellite observation Retrieval algorithms

and Tools

Final retrieved geophysical

information

SAR Surface roughness

modulation

Swell retrieval

algorithms and ray

tracing

Surface current vorticity at 10km scale

and temporal scales of 3-5 days. Depth ~

10m

Surface roughness

pattern and roughness

gradients

Wind retrieval

algorithms (CMOD,

CDOP)

Wind speed at spatial scales of 1 km and

temporal scales of 3-5 days. Used to

downscale scatterometers winds to

estimate Ekman Current

Radar imaging model sub-meso scale Divergence and

convergence zone of surface current

Range Doppler

anomaly shift

Surface motion in range

direction after sea state

correction (CDOP)

Surface current at the very surface (less

than 50cm) snapshots at spatial

resolution of ~10 km and temporal scale

3 - 10 days. Regional mean surface

current at 10km scale.

Scatterometer Surface roughness Wind retrieval algorithm

CMOD

Vector wind and wind stress curl at

spatial scale of > 20 km and temporal

scale of 12h/1day. Used to estimate

Ekman Current.

Altimeter Sea surface height Mean sea surface and

sea level anomaly

Geostrophic current at spatial scale of >

30 km and temporal scale of 5 to 10

days.

GOCE Geoid Mean dynamic

topography

Mean geostrophic current at spatial scale

of 100-200 km

Altimeter +

GOCE

Sea surface height

and geoid

Absolute dynamic

topography

Absolute surface geostrophic current at

spatial scale of 30 km. May even be

finer (~10 km) with access to SARM

altimetry data

IR radiometer

Sea surface

temperature and

fronts

(i) Surface quasi-

geostrophic assumption;

(ii) MCC method

Surface geostrophic current at spatial

resolution of ~25km and temporal scale

of about 1 to 10 days depending on

clouds

Feature tracking using MCC gives

estimate of surface current at resolution

lower that interrogation window

Spectrometer Ocean color,

chlorophyll A

distribution and

fronts

Sun-glint

(i) Bio-optical retrieval

algorithm BOREALIS

(ii) MCC method

(iii) Mean square slope

(MSS)

Ocean color distribution associated with

3D mesoscale dynamics in the upper

ocean. Feature tracking using MCC

gives estimate of surface current

MSS anomalies comparable to SAR

based NRCS anomalies.

C-band

microwave

radiometer

Sea surface

temperature and

fronts

Surface quasi-



resolution of ~25 km and temporal scale

of 1 day

L-band

microwave

radiometer

Sea surface salinity

and fronts

Surface quasi-



resolution of ~100 km and temporal

scale > 3-10 days Table 1:. Overview of satellite sensors, observed quantities, retrieval algorithms and final derived variables.


In its first version, the global current product of Globcurrent is based on the synergy of

altimetry, gravimetry, in-situ and wind stress data together with model outputs for the Stokes

drift and the tidal currents.

Different components of the global currents have been computed on a 1/10° resolution grid, at a

3-hourly temporal resolution, and are accessible via the GlobCurrent portal

http://www.globcurrent.org/:

- Geostrophic currents (see the product handbook [AD-7])

- Ekman currents (see the specific product handbook [AD-8])

- Combined Geostrophic+Ekman currents (see the specific product handbook [AD-9])

- Stokes drift (see the specific product handbook [AD-10])

- Tidal currents (this handbook)

1.2. Purpose and scope of this document

The purpose of this Product Data Handbook is to describe the tidal current products of the first

GlobCurrent system.

1.3. Document structure

This document is organized into the following sections:

Section 1 is the present introduction

Section 2 gives the definition of tidal currents.

Section 3 gives a complete description of the GlobCurrent V1 tidal current products

Section 4 gives some validation results

Section 5 gives the format and structure of the GlobCurrent tidal current product files.

1.4. Applicable Documents

[AD-1] Statement of Work for DUE GlobCurrent project (SoW), EOP-SM/2450, Issue 2, 26

March 2013

[AD-2] Requirement Baseline document for GlobCurrent V1 (RB-1) Deliverable D-040 of the

GlobCurrent project, issued on April, 22 2014.

[AD-3] Technical Note (TN-1). Deliverable D-140 of the GlobCurrent project, issued on April,

29 2014.

[AD-4] Technical Note (TN-2). Product Format and content. Deliverable D-150 of the

GlobCurrent project, issued on December, 5 2014.

[AD-5] Algorithm Theoretical Baseline Document (ATBD-1). Deliverable D-160 of the

GlobCurrent project, issued on December, 5 2014.

[AD-6] The SSALTO/DUACS User Handbook

(http://www.aviso.oceanobs.com/fileadmin/documents/data/tools/hdbk_duacs.pdf)

http://www.globcurrent.org/

http://www.aviso.oceanobs.com/fileadmin/documents/data/tools/hdbk_duacs.pdf


[AD-7] GlobCurrent Data Product Handbook. The geostrophic currents. Deliverable D-280 of

the GlobCurrent project, issued on May, 12th

2015.

[AD-8] GlobCurrent Data Product Handbook. The Ekman currents. Deliverable D-280 of the

GlobCurrent project, issued on May, 12th

2015.

[AD-9] GlobCurrent Data Product Handbook. The combined Geostrophic + Ekman currents.

Deliverable D-280 of the GlobCurrent project, issued on May, 12th

2015.

[AD-10] GlobCurrent Data Product Handbook. The stokes drift. Deliverable D-280 of the

GlobCurrent project, issued on May, 12th

2015.

1.5. Reference documents

The following are the publications and web sites relevant to this document.

1.5.1. Publications

Carrère L., F. Lyard, M. Cancet, A. Guillot, L. Roblou, FES2012: A new global tidal model

taking taking advantage of nearly 20 years of altimetry, Proceedings of meeting "20 Years

of Altimetry", Venice 2012.

D. Stammer, R.D. Ray, O.B. Andersen, B.K. Arbic, W. Bosch, L. Carrere, Y. Cheng, D.S. Chinn,

B.D. Dushaw, G.D. Egbert, S.Y. Erofeeva, H.S. Fok, J.A.M. Green, S. Griths, M.A. King,

F.G Lemoine, S.B. Luthcke, F. Lyard, J. Morison, M. Muller, L. Padman, J.G. Richman,

J.F. Shriver, C.K. Shum, E. Taguchi, Y.Yi, 2014: Accuracy assessment of global barotropic

ocean tide models, Rev. Geophys., 52, 243–282, doi:10.1002/2014RG000450.

1.5.2. Web sites

[WEB-1] GlobCurrent external web site http://www.globcurrent.org

[WEB-2] GlobCurrent internal web site http://globcurrent.nersc.no

[WEB-3] DUE web site http://due.esrin.esa.int

[WEB-4] WAVEWATCH III http://polar.ncep.noaa.gov/waves/wavewatch/wavewatch.shtml

1.6. Acronyms and abbreviations

AATSR Advanced Along Track Scanning Radiometer (of ENVISAT) ADB

AMOC Actions Data Base

Atlantic Meridional Overturning Circulation AMSRE

AOI

AOML

Advanced Microwave Scanning Radiometer – E (of EoS Aqua)

Area Of Interest

Atlantic Oceanographic and Meteorological Laboratory AQUARIUS

AR

ARR

Salinity mission (of NASA/CONAE)

Acceptance Review

Acceptance Review Report

http://dx.doi.org/10.1002/2014RG000450

http://www.globcurrent.org/

http://globcurrent.nersc.no/

http://due.esrin.esa.int/

http://polar.ncep.noaa.gov/waves/wavewatch/wavewatch.shtml


ASAR Advanced Synthetic Aperture Radar (of ENVISAT) ASCAT Advanced SCATterometer (of MetOp) ATBD

ATSR Algorithm Theoretical Basis Document

Along Track Scanning Radiometer AVHRR

Camshift - CC

Advanced Very High Resolution Radiometer

Continuously adaptive mean shift

CDR

CTD Critical Design Review

Conductivity Temperature Depth DIR Directory (of project participants) DMSP Defense Meteorological Satellite Program (of the USA) DUE Data User Element

ENVISAT Environnent Satellite (http://envisat.esa.int) ESA European Space Agency EO Earth Observation EU European Union FAQ Frequently Asked Questions

FR

GOCE Final Report

Gravity field and Ocean Circulation Experiment GOCI

GRACE

HRPT

Geostationary Ocean Color Imager

Gravity Recovery And Climate Experiment

High-resolution Picture Transmission

Hs

ICD Significant Wave Height (also SWH)

Interface Control Document ITT Invitation To Tender KO

MDT Kick-Off

Mean Dynamic Topography MR Monthly Report MTR Mid-Term Review MDB Match-Up DataBase MetOp

MTF

Meteorological Operational (Satellite)

Modulation Transfer Function

MMDB

MSS Multi-sensor Match-up DataBases

Mean Sea Surface

NOP Numerical Ocean Prediction NWP OSC

OSCAR

Numerical Weather Prediction Ocean surface current

Ocean Surface Current Analysis Real-Time PAR Preliminary analysis report PM Progress meeting PMP Project Management Plan PMR

QR

QRR

Passive Microwave Radiometry

Qualification Review

Qualification Review Report RA-2 Radar Altimeter 2 (of ENVISAT) RB Reference Baseline RD

RMS

SAP

Reference Document

Root Mean Square

Scientific Analysis Plan

SAR Synthetic Aperture RADAR


SAR Scientific Assessment Report (of SOS) SD-DAC Surface Drifter – Data Assembly Center SIAR

SLA Scientific and Impact Assessment Report

Sea Level Anomaly SMOS Soil Moisture and Ocean Salinity (mission) SOS Surface Ocean Salinity and Synergy (project) SoW

SPR Statement of Work

Software Problem Report SR Scientific Roadmap SRR System Requirements Review SSH Sea Surface Height SSM/I Special Sensor Microwave Imager (of DMSP) SST

STD Sea Surface Temperature

Standard Deviation STSE

SVP Support to Science Element

Surface Velocity Program SWH Significant Wave Height

TBC To Be Confirmed TBD To Be Determined TDP Technical Data Package TDS Test Data Set TN Technical Note (short report 10-50 pages) TOA Top of Atmosphere TR UCM

Technical Report (long report > 50 pages) User Consultation Meeting

UM URD

User Manual User Requirements Document

URL Universal Resource Locator WP

XBT Work Package

eXpandable Bathy Thermograph


2. Definition of tidal currents Tides are related to gravitational variations associated to the Sun and Moon alignments, resulting

in periodical changes in water levels.

3. Description of the GlobCurrent V1 global tidal currents Tidal current component of Globcurrent is based on FES2012 model. FES2012 is the last version

of the FES (Finite Element Solution) tide model developed in 2012 (Carrere et al, 2012). It is a

fully revised version of the global hydrodynamic tide solutions initiated by the works of

Christian Le Provost in the early nineties. The new model has been developed, implemented and

validated by the LEGOS, NOVELTIS and CLS, within a CNES funded project. FES2012 takes

advantage of longer altimeter time series, improved modeling and data assimilation techniques,

and more accurate ocean bathymetry. Special efforts have been dedicated to address the major

non-linear tides issue and to the determination of accurate tidal currents. FES2012 is based on

the resolution of the tidal barotropic equations (T-UGO model) in a spectral configuration.

A new original high resolution global bathymetry was built, and a new global finite element grid

(~1.5 million nodes) is used leading to a twice more accurate 'free' solution (independent of in

situ and remote-sensing data) than the FES2004 version. Then the accuracy of this 'free' solution

was improved by assimilating long-term altimetry data (Topex/ Poseidon, Jason-1, Jason-2, ERS-

1, ERS-2 and ENVISAT) through an improved representer assimilation method. Final FES2012

solution shows strong improvement compared to FES2004 and GOT4V8, particularly in coastal

and shelf regions and although no tidal gauge has been assimilated yet. 32 tidal constituents are

distributed on 1/16° grids (amplitude and phase).

4. Validation Figure 1 reproduces Table 5 from the paper by Stammer et al, 2014 in which different global tide

models are compared to tide gauges data.

Figure 1: Comparison of some global tidal models with shelf waters tide stations from (Stammer et al, 2014)


5. Data Format The format of the GlobCurrent V1 products follows the rules and standards described in the

GlobCurrent Product Format and Content document [AD-4].

For example, the file named:

20020202000000-GLOBCURRENT-L4-CURtid_0m-FES2012-v01.0-fv01.0.nc

contains L4 tidal current data at ocean surface produced by GlobCurrent project from

CNES/Legos FES-2012 model (“FES2012”). It contains data for 02 February 2012, was

produced using version 1 of the processor and is version 1.0 of the file. The nominal time of the

analysis is 00:00:00 hours.

Each product file shall provide the following content:

netCDF File

Contents Description Units

Section in

[AD-4] Required

Global Attributes

A collection of required global attributes

describing general characteristics of the

file

Various 4.2 Mandatory

Geolocation Data Information to permit locating data on

regular gridded data. 4.5.1 Mandatory

eastward_tidal_curr

ent_velocity

Estimated northward component of the

tidal current vector. m s-1 13.1 Mandatory

northward_tidal_cur

rent_velocity

Estimated eastward component of the

tidal current vector. m s-1 13.2 Mandatory

northward_tidal_cur

rent_velocity_error

Error on the estimated northward

component of the tidal current vector. m s-1 13.3

Mandatory eastward_tidal_curr

ent_velocity_error

Error on the estimated eastward

component of the tidal current vector. m s-1 13.3

flags Flag mask as described in section 5.4. 13.3 Mandatory

quality_level

Quality level associated with the

retrieved geostrophic current vector as

described in section 5.5 of [AD-4] 13.3 Mandatory

Table 2: General content of a GlobCurrent tidal currentL4 product (L4 CURtid)

The following subsections give a more detailed description and CDL example of each

geophysical variable.


1.1. Variable <eastward_tidal_current_velocity>

Tides are related to gravitational variations associated to the Sun and Moon alignments, resulting

in periodical changes in water levels. This is the eastward component of the tidal current

generated by these variations.

Storage type

definition

Variable name definition Description Unit

float eastward_tidal_current_velocit

y

Estimated northward component of the

tidal currentvector.

m s-1

Description

float eastward_tidal_current_velocity (time, lat, lon) ;

eastward_tidal_current_velocity:long_name = "tidal current: zonal

component";

eastward_tidal_current_velocity:depth = "hs";

eastward_tidal_current_velocity:units = "m s-1" ;

eastward_tidal_current_velocity:coordinates = "lon lat" ;

eastward_tidal_current_velocity:_FillValue = -3.40282e+38;

eastward_tidal_current_velocity:horizontal_scale_range = "10km";

eastward_tidal_current_velocity:temporal_scale_range = "instantaneous";

eastward_tidal_current_velocity:comment = "Estimated from CNES/Legos

FES 2012 model used in altimetry”

eastward_tidal_current_velocity:source = “FES2012”

eastward_tidal_current_velocity:limitations = “???”

Comments

Table 3: CDL example description of variable eastward_tidal_current_velocity


1.2. Variable <northward_tidal_current_velocity>

Tides are related to gravitational variations associated to the Sun and Moon alignments, resulting

in periodical changes in water levels. This is the northward component of the tidal current

generated by these variations.

Storage type

definition


float northward_tidal_current_veloci

ty

Estimated eastward component of the

tidal current vector.

m s-1

Description

float northward_tidal_current_velocity (time, lat, lon) ;

northward_tidal_current_velocity:long_name = "tidal current: meridian

component";

northward_tidal_current_velocity:depth = "hs";

northward_tidal_current_velocity:units = "m s-1" ;

northward_tidal_current_velocity:coordinates = "lon lat" ;

northward_tidal_current_velocity:_FillValue = -3.40282e+38;

northward_tidal_current_velocity:horizontal_scale_range = "10km";

northward_tidal_current_velocity:temporal_scale_range =

"instantaneous";

northward_tidal_current_velocity:comment = "estimated from CNES/Legos

FES 2012 model used in altimetry";

northward_tidal_current_velocity:source = “FES2012”

northward_tidal_current_velocity:limitations = “???”

Comments

Table 4: CDL example description of variable northward_tidal_current_velocity


1.3. Variable <eastward_tidal_current_velocity_error>

This is the estimated error on the eastward component of the tidal current.

Storage type

definition


float eastward_tidal_current_velocit

y_error

Error on the estimated northward

component of the tidal current vector.

m s-1

Description

float eastward_tidal_current_velocity_error (time, lat, lon) ;

eastward_tidal_current_velocity_error:long_name = "error on the

estimation of the tidal current velocity: zonal component";

eastward_tidal_current_velocity_error:depth = "hs";

eastward_tidal_current_velocity_error:units = "m s-1" ;

eastward_tidal_current_velocity_error:coordinates = "lon lat" ;

eastward_tidal_current_velocity_error:_FillValue = -3.40282e+38;

Comments

Table 5: CDL example description of variable eastward_tidal_current_velocity_error

1.4. Variable <northward_tidal_current_velocity_error>

This is the estimated error on the northward component of the tidal current.

Storage type

definition


float northward_tidal_current_veloci

ty_error

Error on the estimated eastward

component of the tidal current vector.

m s-1

Description

float northward_tidal_current_velocity_error (time, lat, lon) ;

northward_tidal_current_velocity_error:long_name = "error on the

estimation of the tidal current velocity: meridional component";

northward_tidal_current_velocity_error:depth = "hs";

northward_tidal_current_velocity_error:units = "m s-1" ;

northward_tidal_current_velocity_error:coordinates = "lon lat" ;

northward_tidal_current_velocity_error:_FillValue = -3.40282e+38;

Comments

Table 6: CDL example description of variable northward_tidal_current_velocity_error


1.5. Variable <flags>

The variable flags is used to record any additional information considered important for the

user of a data set. It follows the generic form described in table 4.21 and detailed content

provided in [AD-4].

Storage

type

definition


short flags The variable flags is used to

(a) define the type of surface of the

pixel,

(b) pass through native flags from

the input data set and

(c) record any additional

information considered important

for the user of an L2P data set.

Bit field

Example CDL Description

short flags(time, lat, lon) ;

flags:long_name = "flags" ;

flags:coordinates = "lon lat" ;

flags:valid_min = 0s;

flags:valid_max = 2047s;

flags:flag_meanings = "land ice lake river”;

flags:flag_masks = 1s, 2s, 4s, 8s ;

flags:comment = “These flags are important to properly use the data”

Comments

The meaning of each bit of the variable flags shall be detailed in its flag_meanings and

flag_masks attributes

b0:1 = land surface;

b1:1 = ice contamination;

b2:1 = input data over lake surface;

b3:1 = input data over river;

b4:b15 set by the data provider.

For this variable there is no _FillValue attribute.

Table 7:CDL example description of flags variable


1.6. Variable <quality_level> The variable ‘quality_level provides an indicator of the overall quality of a current

measurement in a GlobCurrent file. It follows the generic form described in Table 8 and detailed

content provided in section 5.5 of [AD-4].

Storage

type

definition


byte quality_level Overall indicator of ocean current

measurement quality

enumer

ate

Example CDL Description

byte quality_level (time, lat, lon) ;

quality_level:long_name = "quality level of ocean current pixel" ;

quality_level:coordinates = "lon lat" ;

quality_level:_FillValue = -128b;

quality_level:valid_min = 0b;

quality_level:valid_max = 5b;

quality_level:flag_meanings = "no_data bad_data worst_quality

low_quality acceptable_quality

best_quality" ;

quality_level:flag_values = 0b, 1b, 2b, 3b, 4b, 5b ;

quality_level:comment = “These are the overall quality indicators and

are used for all GlobCurrent products”

Comments

Table 8: CDL example description of quality_level variable


6. Summary table of product information

A summary of the product information is given in the table below:

Typical file size

(Mbytes)

51 (limited temporal coverage)

Accuracy See section 4 and paper by (Stammer et al, 2014)

How to access Products can be accessed freely and openly. They have been assembled

onto a single thematic platform and are available through various

means:

o FTP

o OpenDAP

o THREDDS

o Remote access and procesing of GlobCurrent data is also

possible through Nephelae cloud

For FTP access, (simple!) registration is required to keep track of the

usage of these products.

Contact information For any issues with data access, please contact our user desk at

[email protected]

For any question on how the product was calculated, please contact

Marie-Hélène RIO at [email protected]

For any question on data format contact Jean-François Piollé at

[email protected]

7. Example read software Users who wish to read (or convert to ASCII or text) GlobCurrent netCDF files, please see many

options at the netCDF FAQ page:

http://www.unidata.ucar.edu/software/netcdf/docs/ncFAQ.html

Users with a THREDDS-enabled python distribution can access directly the GlobCurrent data

archive online via THREDDS, as in

from netCDF4 import Dataset

gcfile =

Dataset("http://tds0.ifremer.fr/thredds/GLOBCURRENT/GLOBAL_010_DEG/GC_MOD_TIDE_GLO_010_FES20

12_FULL_TIME_SERIE")

print gcfile

gcfile.close()

Further examples are given at unidata.github.io/netcdf4-python/

A full CDL dump of the product is given in Appendix.

http://www.ifremer.fr/opendap/cerdap1/globcurrent/global_010_deg/contents.html

http://tds0.ifremer.fr/thredds/GLOBCURRENT/GLOBAL_010_DEG/GLOBAL_010_DEG.html

http://cersat.ifremer.fr/oceanography-from-space/our-domains-of-research/mass-data-processing-and-mining

mailto:[email protected]


http://www.unidata.ucar.edu/software/netcdf/docs/ncFAQ.html

%22http:/tds0.ifremer.fr/thredds/GLOBCURRENT/GLOBAL_010_DEG/GC_MOD_TIDE_GLO_010_FES2012_FULL_TIME_SERIE%22

%22http:/tds0.ifremer.fr/thredds/GLOBCURRENT/GLOBAL_010_DEG/GC_MOD_TIDE_GLO_010_FES2012_FULL_TIME_SERIE%22


8. Frequently Asked Questions

If needed, users can consult the FAQ section from the GlobCurrent web site:

http://globcurrent.ifremer.fr/project/faq

9. Feedback form Users can report problems and request further information by using the feedback form available

at:

http://web.nersc.no/globcurrent/

or by writing to [email protected]

10. Appendix: full CDL dump

netcdf \20120920000000-GLOBCURRENT-L4-TIDE-FES2012-Ifremer-v01.0-fv01.0 {

dimensions:

time = UNLIMITED ; // (1 currently)

lat = 1600 ;

lon = 3600 ;

variables:

float lat(lat) ;

lat:_FillValue = 9.96921e+36f ;

lat:long_name = "latitude" ;

lat:standard_name = "latitude" ;

lat:units = "degrees_north" ;

lat:axis = "Y" ;

float lon(lon) ;

lon:_FillValue = 9.96921e+36f ;

lon:long_name = "longitude" ;

lon:standard_name = "longitude" ;

lon:units = "degrees_east" ;

lon:axis = "X" ;

double time(time) ;

time:_FillValue = 9.96920996838687e+36 ;

time:long_name = "julian day (UT)" ;

time:standard_name = "time" ;

time:units = "days since 1990-01-01T00:00:00Z" ;

time:conventions = "relative julian days with decimal part (as parts of the day )" ;

time:axis = "T" ;

http://globcurrent.ifremer.fr/project/faq

http://web.nersc.no/globcurrent/



double eastward_tidal_current(time, lat, lon) ;

eastward_tidal_current:_FillValue = 9.96920996838687e+36 ;

eastward_tidal_current:long_name = "eastward tidal current" ;

eastward_tidal_current:units = "m s-1" ;

eastward_tidal_current:model = "fes2012" ;

eastward_tidal_current:source = "GlobCurrent" ;

double northward_tidal_current(time, lat, lon) ;

northward_tidal_current:_FillValue = 9.96920996838687e+36 ;

northward_tidal_current:long_name = "northward tidal current" ;

northward_tidal_current:units = "m s-1" ;

northward_tidal_current:model = "fes2012" ;

northward_tidal_current:source = "GlobCurrent" ;

// global attributes:

:Conventions = "CF-1.6, Unidata Observation Dataset v1.0" ;

:netcdf_version_id = "4.3.0 of Jul 8 2013 12:17:12 $" ;

:date_created = "20141031T095328Z" ;

:date_modified = "20141031T095328Z" ;

:id = "GC_MOD_TIDE_GLO_010_FES2012" ;

:naming_authority = "fr.ifremer.cersat" ;

:institution = "Institut Francais de Recherche et d\'Exploitation de la Mer/Centre

de Recherche et d\'Exploitation satellitaire" ;

:institution_abbreviation = "ifremer/cersat" ;

:title = "Tidal currents on GlobCurrent grid" ;

:summary = "Tidal currents from FES2012 model by CNES/LEGOS." ;

:cdm_feature_type = "grid" ;

:keywords = "Oceans > Ocean circulation > Ocean currents" ;

:keywords_vocabulary = "NASA Global Change Master Directory (GCMD)

Science Keywords" ;

:standard_name_vocabulary = "NetCDF Climate and Forecast (CF) Metadata

Convention" ;

:scientific_project = "GlobCurrent" ;

:acknowledgement = "Original FES2012 model provided by CNES/LEGOS

through AVISO" ;

:license = "Free and open" ;

:format_version = "GlobCurrent v1.0" ;

:history = "" ;

:publisher_name = "ifremer/cersat" ;

:publisher_url = "http://cersat.ifremer.fr" ;

:publisher_email = "[email protected]" ;

:creator_name = "Jean-Francois Piolle" ;


:creator_url = "" ;

:creator_email = "[email protected]" ;

:processing_software = "Cersat/Cerbere 1.0" ;

:processing_level = "4" ;

:references = "http://www.aviso.oceanobs.com/en/data/products/auxiliary-

products/global-tide-fes2004-fes99/description-fes2012.html" ;

:geospatial_lat_min = -79.95f ;

:geospatial_lat_max = 79.95f ;

:geospatial_lat_units = "degrees" ;

:geospatial_lon_min = -179.95f ;

:geospatial_lon_max = 179.95f ;

:geospatial_lon_units = "degrees" ;

:geospatial_vertical_min = "" ;

:geospatial_vertical_max = "" ;

:geospatial_vertical_units = "meters above mean sea level" ;

:geospatial_vertical_positive = "up" ;

:time_coverage_start = "20120920T000000Z" ;

:time_coverage_stop = "20120920T000000Z" ;

:time_coverage_resolution = "3-hourly" ;

:geospatial_lat_resolution = 0.09999847f ;

:geospatial_lon_resolution = 0.09999084f ;