PRODUCT USER MANUAL
Sea Level Ocean Monitoring Indicators for:
GLOBAL_OMI_SL_area_averaged_anomalies
GLOBAL_OMI_SL_regional_trends
BALTIC_OMI_SL_area_averaged_anomalies
BLKSEA_OMI_SL_area_averaged_anomalies
IBI_OMI_SL_area_averaged_anomalies
MEDSEA_OMI_SL_area_averaged_anomalies
NORTHEWESTSHELF_OMI_SL_area_averaged_anomalies
Issue: 2.3
Contributors: Jean-François Legeais
Approval Date: 16 January 2020
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CHANGE RECORD
Issue Date § Description of Change Author Validated By
1.0 02/02/2018 All Creation of the document JF Legeais
2.0 26/07/2018 All New supporting material, new regional MSL. Use of the reprocessed DUACS DT-2018 products with updated temporal coverage
JF Legeais
2.1 25/01/2019 ALL Evolution after review comments from MO JF Legeais
2.2 09/10/2019 II, III Evolution following the update of the time series
JF Legeais
2.3 16/01/2020 II.1, II.2
Addition of global mean sea level corrected for TOPEX-A drift.
JF Legeais C.Derval
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TABLE OF CONTENTS
GLOSSARY AND ABBREVIATIONS .................................................................................................................. 4
I INTRODUCTION ......................................................................................................................................... 5
I.1 Summary ...................................................................................................................................................... 5
II DESCRIPTION OF THE PRODUCT SPECIFICATION .......................................................................... 6
II.1 General Information about the products ................................................................................................. 6
II.2 Details of the datasets ................................................................................................................................ 9
II.3 Product System Description .................................................................................................................... 12
II.4 How to download a product .................................................................................................................... 12
i. Download a product through the CMEMS Web Portal Ftp Service .................................................... 12
III FILES NOMENCLATURE and FORMAT ........................................................................................... 13
III.1 Nomenclature of files when downloaded through the CMEMS FTP Services ................................. 13
III.2 File Format: format name ..................................................................................................................... 13
III.3 File size .................................................................................................................................................... 14
III.4 Reading Softwares .................................................................................................................................. 14
IV References .................................................................................................................................................... 15
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GLOSSARY AND ABBREVIATIONS
CMEMS Copernicus Marine Environment Monitoring Service
MSL Mean Sea Level
NetCDF Network Common Data Form
OMI Ocean Monitoring Indicator
PUM Product User Manual
QUID Quality Information Document
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I INTRODUCTION
I.1 Summary
This document is the user manual for the CMEMS Sea Level Ocean Monitoring Indicators (OMI) including different products and associated datasets.
The products are published on the CMEMS dissemination server after automatic and delayed-mode quality controls. The products are available online and disseminated through the CMEMS Information System. Files downloaded are in NetCDF format and follow CF-1.7 convention.
In addition, supporting material is provided in the online catalogue including the regional mean sea level anomalies during the last year of the record. Only the figure is provided.
Disclaimer: The quality of the product may vary during the proposed time series depending on the possible update of the system.
The different sea level OMI products are described in the Quality Information Document (QUID) CMEMS-OMI-SEALEVEL-QUID.pdf (http://cmems-resources.cls.fr/documents/QUID/CMEMS-OMI-QUID-GLO-SL.pdf). See also News flash. More detailed information can be obtained from http://marine.copernicus.eu/services-portfolio/contact-us/
History of change
02/02/2018 Publication of OMI Sea Level products
26/07/2018 Description of the new supporting material, new regional Mean Sea Level. Use of reprocessed DUACS DT-2018 products and updated temporal coverage.
25/01/2019 Evolution after review comments from MO
09/10/2019 Evolution following the update of the time series
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II DESCRIPTION OF THE PRODUCT SPECIFICATION
II.1 General Information about the products
Product(s) name GLOBAL_OMI_SL_area_averaged_anomalies
Geographical coverage Global Ocean
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals and the same filtered and unfiltered timeseries corrected for the TOPEX-A instrumental drift during 1993-1998
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
Product(s) name GLOBAL_OMI_SL_regional trends
Geographical coverage Global Ocean
Variables Map of the altimeter regional sea level trends (sea surface heights above sea level)
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Time integrated
Integration depth (for example..)
Surface
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Format NetCDF CF1.7
Product(s) name BALTIC_OMI_SL_area_averaged_anomalies
Geographical coverage Baltic Sea
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals.
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
Product(s) name BLKSEA_OMI_SL_area_averaged_anomalies
Geographical coverage Black Sea
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals.
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
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Product(s) name IBI_OMI_SL_area_averaged_anomalies
Geographical coverage Iberia-Biscay-Ireland
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals.
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
Product(s) name MEDSEA_OMI_SL_area_averaged_anomalies
Geographical coverage Mediterranean Sea
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals.
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
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Product(s) name NORTHWESTSHELF_OMI_SL_area_averaged_anomalies
Geographical coverage North-West Shelf
Variables Filtered and unfiltered time series of altimeter sea level anomalies (sea surface heights above sea level), adjusted from annual and semi-annual signals.
Update frequency Once per year
Available time series 1993-01-01 to about 5-6 months delay with present time
Delivery mechanism FTP
Temporal resolution Daily
Integration depth (for example..)
Surface
Format NetCDF CF1.7
Detailed information on the systems and products are on CMEMS web site:
http://cmems-resources.cls.fr/documents/QUID/CMEMS-OMI-QUID-GLO-SL.pdf
II.2 Details of the datasets
For each product, one table with details of datasets content
GLOBAL_OMI_SL_area_averaged_anomalies
glo
bal_
om
i_sl_
are
a_avera
ged
_an
om
alies
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the global ocean derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level sla_filtered_tpacorr [m] Sea Level Anomalies sea_surface_height_above_sea_level
sla_tpacorr [m] Sea Level Anomalies sea_surface_height_above_sea_level
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GLOBAL_OMI_SL_regional trends
glo
bal_
om
i_sl_
r
eg
ion
al_
tre
nd
s Map of the altimeter regional mean sea level trends in the global ocean. The trends are not corrected for the
GIA effect.
msl_trend [mm/yr] Regional mean sea level trends tendency_of_sea_surface_height_above_sea_level
BALTIC_OMI_SL_area_averaged_anomalies
balt
ic_
om
i_sl_
are
a_
avera
ge
d_
a
no
malies
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the Baltic Sea derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level
BLKSEA_OMI_SL_area_averaged_anomalies
blk
sea_
om
i_sl_
are
a_avera
ged
_a
no
ma
lie
s
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the Black Sea derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level
IBI_OMI_SL_area_averaged_anomalies
ibi_
om
i
_sl_
are
a_avera
ged
_a
n
om
alie
s
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the Iberian-Biscay-Irish area derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the
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GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level
MEDSEA_OMI_SL_area_averaged_anomalies
med
se
a_o
mi_
sl_
are
a_avera
ged
_
an
om
alies
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the Mediterranean Sea derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level
NORTHWESTSHELF_OMI_SL_area_averaged_anomalies
no
rth
we
sts
helf
_o
mi_
sl_
are
a_av
era
ged
_a
no
mali
es
Altimeter mean sea level daily evolution (filtered and unfiltered) estimated in the European North-West Shelf region derived from the average of the gridded sea level maps weighted by the cosine of the latitude. The timeseries is low-pass filtered, the annual and semi-annual periodic signals are adjusted. The curves are corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004).
sla_filtered [m] Sea Level Anomalies sea_surface_height_above_sea_level sla [m] Sea Level Anomalies sea_surface_height_above_sea_level
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II.3 Product System Description
The CMEMS sea level OMIs are derived from the delayed-time altimeter sea level gridded products generated by the DUACS altimeter production system and distributed by the Copernicus Climate Change Service (C3S) since these products are designed for climate applications. The DUACS altimeter processing sequences can be divided into the following main steps (details are described in Pujol et al., 2016):
Acquisition
Pre-processing homogenization
Input data quality control
Multi-mission cross-calibration
Along-track products generation
Gridded merged products generation
Final quality control
Among them, the multi-mission cross-calibration process ensures that all data flows from all satellites have consistent and accurate information. This allows the reduction of various sources of geographically correlated error patterns and ensures an optimal homogenization of the dataset. Global and regional biases between two successive altimeter missions are reduced and finally, the multi-mission along-track measurements are mapped thanks to an optimal interpolation method on a daily ¼° x ¼° regular grid. Additional information on the data processing can be found in Pujol et al. (2016), Ablain et al. (2017) and Escudier et al. (2017).
II.4 How to download a product
i. Download a product through the CMEMS Web Portal Ftp Service
You first need to register. Please find below the registration steps: http://marine.copernicus.eu/web/34-products-and-services-faq.php#1
Once registered, the CMEMS FAQ http://marine.copernicus.eu/web/34-products-and-services-faq.php will guide you on how to download a product through the CMEMS Web Portal FTP Service.
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III FILES NOMENCLATURE AND FORMAT
III.1 Nomenclature of files when downloaded through the CMEMS FTP Services
The CMEMS sea level OMI files nomenclature when downloaded through the CMEMS FTP Services is based on the following nomenclature:
<datasetname>_<timestep>_P<productiontime>_<freetext>
Where :
<datasetname> is the dataset reference.
<timestep> is the first time step in the file.
<productiontime> is the production time when the file was generated.
<freetext> includes potential additional information.
III.2 File Format: format name
The products are stored using the NetCDF format. NetCDF (network Common Data Form) is an interface for array-oriented data access and a library that provides an implementation of the interface. The NetCDF library also defines a machine-independent format for representing scientific data. Together, the interface, library, and format support the creation, access, and sharing of scientific data. The NetCDF software was developed at the Unidata Program Center in Boulder, Colorado. The NetCDF libraries define a machine-independent format for representing scientific data. Please see Unidata NetCDF pages for more information, and to retrieve NetCDF software package. NetCDF data is:
* Self-Describing. A netCDF file includes information about the data it contains. * Architecture-independent. A NetCDF file is represented in a form that can be accessed by computers with different ways of storing integers, characters, and floating-point numbers. * Direct-access. A small subset of a large dataset may be accessed efficiently, without first reading through all the preceding data. * Appendable. Data can be appended to a NetCDF dataset along one dimension without copying
the dataset or redefining its structure. The structure of a NetCDF dataset can be changed, though this sometimes causes the dataset to be copied.
* Sharable. One writer and multiple readers may simultaneously access the same NetCDF file.
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III.3 File size
DATASET NAME NAME OF FILE DIMENSION [MB]*
Compressed Uncompressed
global_omi_sl_area_averaged_anomalies
global_omi_sl_area_averaged_anomalies_19930101_Pyyyymmdd.nc
N/A 0.2
global_omi_sl_regional_trends
global_omi_sl_regional_trends_19930101_Pyyyymm
dd.nc N/A 4.0
baltic_omi_sl_area_averaged_anomalies
baltic_omi_sl_area_averaged_anomalies_19930101_
Pyyyymmdd.nc N/A 0.2
blksea_omi_sl_area_averaged_anomalies
blksea_omi_sl_area_averaged_anomalies_19930101
_Pyyyymmdd.nc N/A 0.2
ibi_omi_sl_area_averaged_anomalies
ibi_omi_sl_area_averaged_anomalies_19930101_Py
yyymmdd.nc N/A 0.2
medsea_omi_sl_area_averaged_anomalies
medsea_omi_sl_area_averaged_anomalies_1993010
1_Pyyyymmdd.nc N/A 0.2
northwestshelf_omi_sl_area_averaged_anomalies
northwestshelf_omi_sl_area_averaged_anomalies_19930101_Pyyyymmdd.nc
N/A 0.2
III.4 Reading Softwares
The products are stored using the NetCDF-CF format. Note that these data can be browsed and used through several softwares, like:
Basic Radar Altimetry Toolbox: http://www.altimetry.info ncBrowse: http://www.epic.noaa.gov/java/ncBrowse/
NetCDF Operator (NCO): http://nco.sourceforge.net/
http://www.unidata.ucar.edu/software/netcdf/
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IV REFERENCES
See the Quality Information Document (QUID) CMEMS_OMI_SEALEVEL_QUID.pdf (http://cmems-resources.cls.fr/documents/QUID/CMEMS-OMI-QUID-GLO-SL.pdf).
Pujol, M.-I., Faugere, Y,. Taburet, G., Dupuy, S., Pelloquin, C., Ablain, M., and Picot, N.: DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years, Ocean Sci., 12, 1067-1090. doi: 10.5194/os-12-1067-2016, 2016.
Ablain, M., Legeais, J.-F., Prandi, P., Marcos, M., Fenoglio-Marc, L., Dieng, H.-B., Benveniste, J. and Cazenave, A.: Satellite altimetry-based sea level at global and regional scales, Surv Geophys., 38, 7-31. doi: 10.1007/s10712-016-9389-8, 2017.
Escudier, P. A. Couhert, F. Mercier, A. Mallet, P. Thibaut, N. Tran, L. Amarouche, B. Picard, L. Carrère, G. Dibarboure, M. Ablain, J. Richard, N. Steunou, P. Dubois, M. H. Rio, J. Dorandeu (2017) Satellite radar altimetry: principle, geophysical correction and orbit, accuracy and precision, In CRC Book on satellite altimetry, guest editors Stammer, D. and Cazenave, A.