Marine Monitoring

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This slideshow gives an overview of the CMEMS Sea Level Satellite Products

LEVEL1 – For Beginners- Slides have been prepared in Nov 2016

C M E M S S e a L e v e l S a t e l l i t e P r o d u c t s

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

W H A T I S S A T E L L I T E A L T I M E T R Y ? ( 1 / 3 )

• SATELLITE SEA LEVEL is measured

by a sensor called « altimeter or SAR

altimeter » on board of several

satellites.

• The altimeter measures the sea

surface height at the surface of the

ocean with respect to a reference

level.

Marine Monitoring

W H A T I S S A T E L L I T E A L T I M E T R Y ? ( 2 / 3 )

• Altimeters determine the distance between the satellite

and the ocean surface by measuring the time it takes a

radar pulse to travel from the satellite to the ocean

surface and back.

• The systems for determining the satellite precise location

in orbit (« DORIS », GPS and laser) are also a critical

element for obtaining accurate sea surface height, since

it gives the reference.

Marine Monitoring

W H A T D O E S S A T E L L I T E M E A S U R E ? ( 3 / 3 )

SEA SURFACE HEIGHT

RANGE

altitude

SEA SURFACE HEIGHT = altitude – RANGE – Corr

Satellite measures the

SEA SURFACE HEIGHT by

substracting the RANGE

(satellite-to-surface distance)

and various CORRECTIONS

(environment, instrument, sea

state, geophysical corrections)

to the satellite altitude

measurement.

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

A l t i m e t r y i s n o t i m a g e r y … ( f o r n o w )

NB. basically altimetry data

are “along-track”, i.e. a

narrow thread of

measurements just beneath

the satellite

Sea Level Anomaly on May , 12-14th (cm) From Jason-2, Altika, Cryosat-2 and HY2A

Marine Monitoring

W H I C H C H A R A C T E R I S T I C S ?

Sea Level satellite data provide with Sea Level properties:

• In 1 dimension, just beneath the satellite = along-track

AND in 2 dimensions, on a longitude-latitude (regular) grid

Marine Monitoring

W H I C H C H A R A C T E R I S T I C S ?

• Sea Level satellite data provide with Sea Level properties:

• In 2 dimensions (at the ocean surface, displayed on a 2D grid)

• Through a period of time:

• A reprocessing of the past (CMEMS provides with ~20

years in the past)

• An analysis of the current conditions

• No forecast into the future is provided.

• Each grid map represents the day it is dated from (it is

not, and has never been, a mean)

Marine Monitoring

W H I C H P A R A M E T E R S ?

CMEMS SEA LEVEL Satellite products provide with the following information:

• SEA SURFACE HEIGHT ANOMALY, i.e. sea surface height with respect to a

several-year mean (ssh variability)

• & derived geostrophic current velocities

computed from surface slopes ; include “only” current variability

• SEA SURFACE ABSOLUTE HEIGHT, i.e. sea surface height with respect to the

geoid (absolute dynamic topography)

• & derived geostrophic current velocities

computed from surface slopes ; includes mean currents’ flow (Gulf Stream,

Kuroshio…)

Those data were formerly distributed through the Aviso center

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

W H A T I S C M E M S A D D E D V A L U E ? ( 1 / 3 )

L0 L1 L2 L3 L4

CMEMS PRODUCTS PROCESSING LEVEL

Raw Satellite

Data Raw Satellite

Data with

correction

Derived

geophysical

variables at

same

resolution and

location as L1

Variables

mapped on

space-time

grid, with

calibration,

merging&

validation

Same as L3

but Gap Free

Grid and with

additional

annexed

information

INCREASING ADDED VALUE OF SATELLITE DATA

Marine Monitoring

W H A T I S C M E M S A D D E D V A L U E ? ( 2 / 3 )

Reprocessed products: A new product every 1 to 2 years with optimal

accuracy and homogeneous time series

Real time products: A new product update every day, a few hours after

sensing

REPROCESSING (20years in the past) Real Time

Marine Monitoring

W H A T I S C M E M S A D D E D V A L U E ? ( 3 / 3 )

• Calibration: all satellites are inter-calibrated, i.e. all satellites use

the same reference level.

• Merging and Interpolation: satellite measures from one or several

satellites are condensed as ONE VALUE on a REGULAR GRID :

gridded product with gaps (L3) and gridded product without gaps

(L4).

• Validation: products are scientifically validated following a

thorough methodology.

• Algorithm and Corrections are specific to each European Sea

characteristics.

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

C M E M S S E A L E V E L T A C D A T A P R O D U C E R S

Marine Monitoring

O u t l i n e

• What is Satellite Altimetry?

• Which Characteristics and Parameters?

• What is CMEMS added value?

• Who are the CMEMS Sea Level Data Producers?

• Which Satellite Sea Level Products in CMEMS

catalogue?

Marine Monitoring

SEA LEVEL Satellite products over the GLOBAL Ocean and all European

Seas are sorted into 2 categories:

• Along Track Sea Level Anomaly L3 Along Track- Real Time and Reprocessed SEALEVEL_(AREA)_SLA_L3_(NRT)or(REP)_OBSERVATIONS_008_XXX

• Gridded Sea Level Anomaly Maps

L4 gridded - Real Time and Reprocessed

SEALEVEL_(AREA)_SLA_MAP_L4_(NRT )or (REP)_OBSERVATIONS_008_XXX

W H I C H P R O D U C T S I N C M E M S C A T A L O G U E ?

Marine Monitoring

A n y q u e s t i o n , a n y t i m e : s e r v i c e d e s k . c m e m s @ m e r c a t o r - o c e a n . e u