exploiting coastal altimetry to improve tidal estimation• tides are a large source of errors in...

Deutsches Geodätisches Forschungsinstitut (DGFI-TUM)Technische Universität München

G. Piccioni, D. Dettmering, C. Schwatke, M. Passaro, F. Seitz

Exploiting coastal altimetry to improve

tidal estimation

Deutsches Geodätisches Forschungsinstitut

Technische Universität München

(DGFI-TUM)

ESA Living Planet Symposium 2019

15 May 2019 | Milan, Italy

Deutsches Geodätisches Forschungsinstitut (DGFI-TUM) | Technische Universität München 2

• Tides are a large source of errors in coastal altimetry

• Coastal issues in tide models

- Accuracy of 1-2 cm in open ocean VS 10 cm at the coast

- High discrepancies among models in coastal areas

• Altimetry is crucial for tide modeling. What about coastal altimetry?

Motivation


Progress in coastal altimetry

Retracking

• Along-track tidal estimations using ALES retracker

• Improvements of 0.5 cm for points closer than 5 km to coast

Improvement

with ALESPiccioni et al. 2018.

Coastal Improvements for

Tide Models: The Impact of

ALES Retracker.

https://doi.org/10.3390/rs1

0050700


Progress in coastal altimetry

Credit:

• Fernandes, M.J.; Lázaro, C. “GPD+ Wet Tropospheric

Corrections for CryoSat-2 and GFO Altimetry

Missions”. Remote Sens. 2016, 8, 851.

• Rio M.-H., Cancet M., Carrère L., Schaeffer P. Tides,

Mean Sea Surface, Geoid (and MDT), at the coast.

Coastal Altimetry Training. Frascati, Italy, 2018.

• Andersen et al. 2018.https://ftp.space.dtu.dk/pub/

DTU18/PRESENTATIONS/DTU18MSS-V2.pdf

GPD+ DTU18MSS

FES2014

Wet tropospheric correction Mean Sea Surface

Ocean tide model

M2


The Empirical Ocean Tide (EOT) model

• EOT19p based on EOT11a (Savcenko and Bosch, 2012)

• SLA are derived using coastal products:

− ALES retracker

− FES2014 tide model

− GPD+ wet troposphere model

− DTU18 mean sea surface

• Variance Component Estimation

(VCE)

According to availability

Weights of J1 in VCE

[ % ]


Elevation differences between models – North Sea

SD(DTU10, FES2012, EOT11a)

M2

K1

cm

Standard Deviation (SD) of latest tide models VS models in Stammer et al. 2014.

SD calculations based on Stammer et al. 2014.


Elevation differences between models – North Sea

SD(DTU10, FES2012, EOT11a) SD(DTU16, FES2014, EOT19p)

M2

K1

cm cm




Elevation differences between models – Malay Archipelago

SD(DTU10, FES2012, EOT11a) SD(DTU16, FES2014, EOT19p)

M2

K1

cm cm




Elevation differences between models

SD in 2015

[cm]

SD in 2019

[cm]

M2 3.33 0.57

N2 0.66 0.19

S2 1.23 0.28

K2 0.41 0.12

K1 0.17 0.09

O1 0.15 0.10

P1 0.91 0.10

Q1 0.12 0.06

RSS 3.75 0.70

North Sea


Elevation differences between models

SD in 2015

[cm]

SD in 2019

[cm]

M2 3.33 0.57

N2 0.66 0.19

S2 1.23 0.28

K2 0.41 0.12

K1 0.17 0.09

O1 0.15 0.10

P1 0.91 0.10

Q1 0.12 0.06

RSS 3.75 0.70

North Sea Malay Archipelago

SD in 2015

[cm]

SD in 2019

[cm]

M2 2.37 1.12

N2 0.52 0.25

S2 1.34 0.49

K2 0.48 0.23

K1 0.81 0.46

O1 0.61 0.39

P1 0.40 0.30

Q1 0.20 0.15

RSS 3.02 1.44


Comparison with EOT11a – North Sea

Improvement of EOT19p at single

stations relative to EOT11aMedian of absolute differences (MAD)

[ % ]

Δ𝑅 =𝑀𝐴𝐷𝐸𝑂𝑇11 −𝑀𝐴𝐷𝐸𝑂𝑇19

𝑀𝐴𝐷𝐸𝑂𝑇11⋅ 100

EOT11a

[cm]

EOT19p

[cm]

ΔR

[%]

M2 3.40 2.29 32.65

N2 1.13 0.85 24.78

S2 1.81 1.36 24.86

K2 3.89 1.87 51.93

K1 3.15 2.23 29.21

O1 2.22 1.51 31.98

P1 0.95 0.79 16.84

Q1 1.15 1.00 13.04

RSS 6.95 4.49 35.39


Comparison with EOT11a – Malay Archipelago

Improvement of EOT19 at single

stations relative to EOT11a

EOT11a

[cm]

EOT19p

[cm]

ΔR

[%]

M2 2.51 1.94 22.71

N2 0.74 0.68 8.11

S2 1.71 1.22 28.65

K2 0.78 0.32 58.97

K1 1.27 1.58 -24.41

O1 0.94 0.59 37.23

P1 0.722 0.50 30.75

Q1 0.28 0.23 17.86

RSS 3.67 2.99 18.53

Median of absolute differences (MAD)

[ % ]


Comparison with other models – North Sea

EOT11a EOT19p FES2014 TPXO8 DTU16 GOT4.8

M2 3.40 2.29 2.98 3.02 2.26 5.01

N2 1.13 0.85 0.96 1.50 1.04 1.77

S2 1.81 1.36 1.32 1.34 1.29 2.34

K2 3.89 1.87 1.86 3.08 2.66 4.36

K1 3.15 2.23 2.05 2.41 2.27 3.25

O1 2.22 1.51 1.66 1.51 1.58 2.87

P1 0.95 0.79 0.73 1.16 0.94 1.07

Q1 1.15 1.00 0.98 1.08 1.09 1.12

RSS 6.95 4.49 4.84 5.77 4.97 8.59

Median of absolute differences (MAD) in cm


Comparison with other models – Malay Archipelago

EOT11a EOT19p FES2014 TPXO8 DTU16 GOT4.8

M2 2.44 1.63 1.98 2.71 4.03 2.95

N2 0.74 0.65 0.52 0.84 1.29 1.35

S2 1.27 1.20 1.05 1.53 1.60 1.81

K2 0.69 0.28 0.42 0.49 1.34 0.83

K1 1.38 1.62 1.34 2.09 1.95 0.91

O1 1.08 0.58 0.78 1.85 0.98 1.29

P1 0.73 0.47 0.50 0.61 1.55 0.86

Q1 0.27 0.23 0.23 0.48 0.34 0.33

RSS 3.50 2.79 2.86 4.36 5.44 4.22

Median of absolute differences (MAD) in cm


• Improved agreement with latest models at the coast:

- from 3.75 cm to 0.7 cm in the North Sea

- from 3.02 cm to 1.44 cm in Indonesia

• Improvement with EOT19p vs EOT11a up to 35%:

- RSS error reduction of ~1.5 cm in the North Sea

- RSS error reduction of ~ 0.7 cm in Indonesia

• Smallest MAD error with EOT19p in both areas

Conclusion & Outlook


• Improved agreement with latest models at the coast:

- from 3.75 cm to 0.7 cm in the North Sea

- from 3.02 cm to 1.44 cm in Indonesia

• Improvement with EOT19p vs EOT11a up to 35%:

- RSS error reduction of ~1.5 cm in the North Sea

- RSS error reduction of ~ 0.7 cm in Indonesia

• Smallest MAD error with EOT19p in both areas

• Understand issues with K1 constituent

• Promising results with EOT19p final goal: global EOT

Conclusion & Outlook


Thank you!More on this:

• Piccioni et al. 2018. Coastal Improvements for Tide Models: The Impact of ALES

Retracker. Remote Sens. 2018, 10(5), 700; https://doi.org/10.3390/rs10050700

• Piccioni et al. 2019. TICON: TIdal CONstants based on GESLA sea-level records from

globally-located tide gauges. RMets Geoscience Data Journal. (in review)

In-situ data:

TICON tide gauge database (in review):https://doi.pangaea.de/10.1594/PANGAEA.896587

TICON was developed with in-situ data from GESLA database: https://gesla.org

Thanks to Richard Ray for providing shallow water gauges (Stammer et al. 2014)

Altimetry data:

DGFI-TUM altimetry data are available on OpenADB at: https://openadb.dgfi.tum.de

https://doi.org/10.3390/rs10050700

exploiting coastal altimetry to improve tidal estimation• tides are a large source of errors in...

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