Post on 17-Jul-2020
COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal 1
PROSPECTS FOR THE USE OF SATELLITE ALTIMETRY IN COASTAL REGIONS
Remko Scharroo,
Hans Bonekamp,
Christelle Ponsard,
Carolina Nogueira-Loddo
EUMETSAT
Darmstadt, Germany
Paolo Cipollini
NOC Southampton, England
3 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Past, current, and future missions
“Reference missions”, to be continued with Jason-3 and Jason-
CS A and B (Sentinel-6)
35-day repeats will likely come to an end
27-day repeats of Sentinel-3
o With SAR and interleaved ground-tracks of S3-A/B
CryoSat-2 still continuing (non-repeat)
SWOT in the planning for 2020.
4 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
SAR Altimetry – quantum leap
Sentinel-3 and -6 in SAR mode over the whole ocean!
The improvements w.r.t. conventional (pulse-limited or ‘LRM’
– Low Resolution Mode) altimetry:
o higher along-track resolution
o better signal to noise ratio
o explained with simple energy considerations in the next
slide
More “looks” = improved SSH retrieval accuracy
Finer spatial resolution along track o ~ 300 meters along-track
Less contamination close to land o Very well suited for coastal
altimetry
5 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
In SAR mode we split the footprint
along-track, and align multiple
looks over the same resolution cell
This portion of the
waveform contributes very
little information
(even less so in the coastal
zone!)
Range, sigma0, SWH
from the leading edge Waveform:
Illuminated surface:
Po
wer
Doppler isolines (along-track SAR processing)
Flight direction
Po
wer
Multilook Averaging
6 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Closed-burst SAR (CryoSat-2 and Sentinel-3)
In a closed-burst SAR (CryoSat, S-3) transmit and receive are not
interleaved and are not continuous.
o The CryoSat values of N = 64 and PRF = 18 kHz give a burst
duration of ~3.5 ms. But the burst-to-burst interval is ~11.8 ms.
70% of the opportunity to make measurements is not used.
This pulsing scheme cannot be used to make an equivalent LRM
measurement.
CryoSat burst interval 11.8 ms
Two-way time at CryoSat altitude (S-3 is similar):
7 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Interleaved LRM or open-burst SAR (Jason-CS)
PRF ~ 9 kHz and continuously interleaved transmit/receive throughout the
ocean.
All possible statistically independent measurements are made.
SAR and LRM can both be made from the same echoes, under the same
conditions.
LRM from simple sequential averaging of all echoes yields optimal LRM
everywhere, both coastal and open ocean.
Since all individual echoes will be downlinked, SAR products also can be
made.
8 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal zone benefits
Higher SNR — can detect small signals in ‘noisy’ (from
the point of view of altimetry observables) coastal
environment
Much higher along-track resolution
o part of it can be traded off, if not needed, in change
for further noise reduction
Reduced contamination by land and coastal targets
(depending on their position relative to satellite track)
Individual echoes — allows editing out affected echoes
or Doppler bins
9 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Assessing SAR mode performance in the coastal zone
Flight
direction
The difference in height between one along-track resolution cell and the next is essentially only due to instrument noise
10 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Faster …
Requirements
Sentinel LRM and SAR data within 3 hours!
NRT and STC data to be delivered faster
o Get used to the new latency names
Near-Realtime Short Time Critical Non Time Critial
OGDR IGDR GDR
Jason-2 3-5 hours 1-2 days 60 days
Jason-2 and -3 3 hours 48 hours 60 days
FDM (LRM only) LRM and SAR
CryoSat-2 3 hours 30 days
NRT STC NTC
Sentinel-3 3 hours 48 hours 60 days
Sentinel-6/Jason-CS 3 hours 36 hours 60 days
11 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Upcoming SAR missions Upcoming SAR Altimetry Missions
Sentinel-6/Jason-CS (2020)
Sentinel-3 (2015)
12 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Cheaper … (?)
Sentinel-3
Altimetry: LRM and SAR modes. Also: SST and Ocean Colour
Sentinel-3A and -3B (~1 year apart; interleaved tracks)
Part of Copernicus program
o EC responsible for ocean data; ESA for land data
o Coast line is going to be in both datasets
Sentinel-6
Dedicated to altimetry; continuing the reference missions
Jason-CS A and B (~5 years apart; interleaved tracks)
To be part of Copernicus program
o EC operation
o Plus NASA, NOAA and CNES
13 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Cheaper …
Data
Still for free, and more of it …
Level 1
o Calibrated instrument data: waveforms and individual echoes
Level 2
o Geophysical Data Records
Level 2P
o As Level 2, with updated corrections, models
Level 3
o Harmonised with other missions
14 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Sentinel-6 (Jason-CS) Product Baseline
Delivery of L0, L1, L2, L3 data by EUMETSAT
Resolution Service
Name Format
User Data Access
EUMETCast GTS ftp (TBC) Archive
Low
(LRM)
NTC NetCDF - - - L2
STC NetCDF - - L1b L1b, L2, L2P, L3
NRT NetCDF
L2 (std +
red) - - L0, L2
BUFR L2 L2 - L2
High
(SAR)
NTC NetCDF - - - L2
STC NetCDF - - L1a, L1b L1a, L1b, L2, L2P, L3
NRT NetCDF
L2 (std +
red) - - L0, L2
BUFR L2 L2 - L2
15 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Better …
Jason-3
“Carbon copy” of Jason-2
Improved radiometer (more stable)
Sentinel-3
LRM mode (will not be used)
SAR mode (over all terrain)
Sentinel-6
LRM and SAR mode simultaneously
16 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Better …
Orbit
Orbit precision is ever improving
DORIS and GPS for operational/on-board orbit determination
Open-loop tracking
This means that the range is estimated on-board
o based on on-board orbit and DEM model
o not on previous measurement
Improves tracking near coasts
Open burst (interleaved mode) LRM/SAR
To be implemented for Sentinel-6/Jason-CS
17 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Error budgets for sea level
Values in centimeters (1-sigma)
For average conditions (2 m wave height)
SAR reduces noise and overall SSH anomaly error
Envisat Sentinel-3 Jason-2 Jason-CS
Altimeter noise (LRM) 1.8 1.7 1.8 1.7
Altimeter noise (SAR) 1.3 0.8
Ionosphere 0.5 0.5 0.5 0.5
Sea state bias 2.0 2.0 2.0 2.0
Dry troposphere 0.7 0.7 0.7 0.7
Wet troposphere 1.4 1.4 1.0 1.0
Orbit error 1.9 1.9 1.0 1.0
SSHA error (LRM) 3.6 3.6 3.2 3.2
SSHA error (SAR) 3.5 2.8
18 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Cryosat-2 the first SAR altimeter in orbit
19 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Cryosat-2 Mode Mask
SAR mode polygons in green SARin mode in purple Rest in conventional LRM mode
20 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Increased noise with Pseudo-LRM compared to LRM Can be handled with some minor smoothing No apparent jumps or discontinuities at transitions
CryoSat-2 LRM / Pseudo-LRM transition
SAR
21 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal performance: a case study
Envisat p0543
(35-day repeat)
Cryosat
single
passes
20 km
22 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal performance: a case study
0 2 4 6 8 100
0.05
0.1
0.15
0.2
0.25
Distance from coast (km)
ab
s(d
iff(T
WLE
20H
z))
Cipollini, Passaro & Vignudelli,
paper in prep.
Envisat p0543 SGDR
(median of 76 passes)
23 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal performance: a case study
0 2 4 6 8 100
0.05
0.1
0.15
0.2
0.25
Distance from coast (km)
ab
s(d
iff(T
WLE
20H
z))
Cipollini, Passaro & Vignudelli,
paper in prep.
Envisat p0543 SGDR
(median of 76 passes)
Envisat p0543 ALES
(median of 76 passes)
24 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal performance: a case study
0 2 4 6 8 100
0.05
0.1
0.15
0.2
0.25
Distance from coast (km)
ab
s(d
iff(T
WLE
20H
z))
Envisat p0543 SGDR
(median of 76 passes)
Envisat p0543 ALES
(median of 76 passes)
CryoSat–2 SAMOSA
(single passes)
Cipollini, Passaro & Vignudelli,
paper in prep.
25 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Coastal performance: a case study
0 2 4 6 8 100
0.05
0.1
0.15
0.2
0.25
Distance from coast (km)
ab
s(d
iff(T
WLE
20H
z))
Envisat p0543 SGDR
(median of 76 passes)
Envisat p0543 ALES
(median of 76 passes)
CryoSat–2 SAMOSA
(median of 11 passes)
CryoSat–2 SAMOSA
(single passes)
Cipollini, Passaro & Vignudelli,
paper in prep.
26 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Important application: storm surges
Surge due to Hurricane Katrina,
29 August 2005
27 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
C2 SAR observations of Xaver storm - Dec2013
Friday 6 Dec 23:05
Data were available on eSurge Server by Saturday lunchtime
DMI model
Madsen et al eSurge: ESA DUE
(Data User Element)
Project for 2011-2015
www.storm-surge.info
28 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
Conclusions
Jason-3 will soon be launched, and will continue 20+ years of
“reference altimeter missions”
Advantages of SAR altimetry over conventional altimetry (higher
resolution, higher SNR, reduced impact of land/bright targets)
are particularly valuable in the coastal zone
o Demonstrated already with excellent Cryosat-2 data
Sentinel-3 will provide global SAR mode coverage – including
the whole world’s coastline
o First “operational coastal altimetry mission”
Sentinel-6 will introduce SAR on the reference altimeter missions
o “Interleaved mode” will allow LRM/SAR simultaneously, thus
excellent to ensure continuity and a lot of R&D
29 COSS-TT/ARCOM Workshop — 31 Aug – 4 Sep 2015 — Lisbon, Portugal
18-19 October 2015, Reston (Virginia), United States
www.coastalaltimetry.org
abstracts due today!