Can Satellite Altimetry Be Used to Map Small Eddies, 25-75 km in Diameter?
14
Can Satellite Altimetry Be Used to Map Small Eddies, 25-75 km in Diameter? Harley E. Hurlburt, Jay F. Shriver, and Ole Martin Smedstad Naval Research Laboratory, Stennis Space Center, MS, USA Planning Systems Inc., Stennis Space Center, MS, USA International GODAE Steering Team Meeting Met Office UK, Exeter, UK 14-16 November 2005
description
Can Satellite Altimetry Be Used to Map Small Eddies, 25-75 km in Diameter? Harley E. Hurlburt, Jay F. Shriver, and Ole Martin Smedstad Naval Research Laboratory, Stennis Space Center, MS, USA Planning Systems Inc., Stennis Space Center, MS, USA International GODAE Steering Team Meeting - PowerPoint PPT Presentation
Transcript of Can Satellite Altimetry Be Used to Map Small Eddies, 25-75 km in Diameter?
Can Satellite Altimetry Be Used to Map Small Eddies, 25-75 km in Diameter?
Harley E. Hurlburt, Jay F. Shriver, and Ole Martin SmedstadNaval Research Laboratory, Stennis Space Center, MS, USA
Planning Systems Inc., Stennis Space Center, MS, USA
International GODAE Steering Team MeetingMet Office UK, Exeter, UK
14-16 November 2005
How well can small eddies, 25-75 km in diameter, be mapped by satellite altimetry assimilated by a high resolution ocean model?
What is the lower bound in size that can be
represented?
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIranSeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS Ocean Color – 2-6 Oct 2002 Composite SeaWiFS Ocean Color – 2-6 Oct 2002 Composite
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS Ocean Color – 2-6 Oct 2002 Composite SeaWiFS Ocean Color – 2-6 Oct 2002 Composite
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIranSeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
Eddies numbered in order of decreasing size
Composite of most Composite of most recent data recent data
Oct 2-Oct 6 2002, Oct 2-Oct 6 2002, most is from Oct 6most is from Oct 6
Comparison of 1/32Comparison of 1/32 Global NLOM and SeaWiFS in the Arabian Sea Global NLOM and SeaWiFS in the Arabian Sea
Oct 6 2002Oct 6 2002
No assimilation of No assimilation of ocean dataocean data
1.0 1.6 2.5 4.0 0.6 0.4 0.3
24°N
22°N
20°N
18°N
16°N
24°N
22°N
20°N
18°N
16°N
26°N 26°N
56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E
SeaWiFS ocean colorSeaWiFS ocean color 1/32° NLOM sea surface height (SSH) and surface currents1/32° NLOM sea surface height (SSH) and surface currents
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Altimeter dataassimilated
No assimilation
(in cm)(in cm)
Both used atmospheric forcing from FNMOC/NOGAPSBoth used atmospheric forcing from FNMOC/NOGAPS
Adapted from Shriver et al. (2005, JMS accepted)Adapted from Shriver et al. (2005, JMS accepted)
(in mg/m(in mg/m33))
http://www.ocean.nrlssc.navy.mil/global_nlomhttp://www.ocean.nrlssc.navy.mil/global_nlom
With assimilation of With assimilation of ERS-2, GFO and JASON 1 ERS-2, GFO and JASON 1
altimeter SSH dataaltimeter SSH data
Oct 6 2002Oct 6 2002
Composite of most Composite of most recent data recent data
Oct 2-Oct 6 2002, Oct 2-Oct 6 2002, most is from Oct 6most is from Oct 6
Comparison of 1/16Comparison of 1/16 and 1/32 and 1/32 Global NLOM and SeaWiFS in the Arabian Global NLOM and SeaWiFS in the Arabian SeaSea
Oct 6 2002Oct 6 2002
1.0 1.6 2.5 4.0 0.6 0.4 0.3
24°N
22°N
20°N
18°N
16°N
24°N
22°N
20°N
18°N
16°N
26°N 26°N
56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E
SeaWiFS ocean colorSeaWiFS ocean color NLOM sea surface height (SSH) and surface currentsNLOM sea surface height (SSH) and surface currents
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
1/32 NLOM 1/16 NLOM
(in cm)(in cm)
Both used atmospheric forcing from FNMOC/NOGAPSBoth used atmospheric forcing from FNMOC/NOGAPS
Adapted from Shriver et al. (2005, JMS accepted)Adapted from Shriver et al. (2005, JMS accepted)
(in mg/m(in mg/m33))
http://www.ocean.nrlssc.navy.mil/global_nlomhttp://www.ocean.nrlssc.navy.mil/global_nlom
Oct 6 2002Oct 6 2002
With assimilation of With assimilation of ERS-2, GFO and JASON 1 ERS-2, GFO and JASON 1
altimeter SSH dataaltimeter SSH data
With assimilation of With assimilation of ERS-2 and GFO altimeter ERS-2 and GFO altimeter
SSH dataSSH data
(in cm)(in cm)
24°N
22°N
20°N
18°N
16°N
26°N
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E
29 Sept 2002 6 Oct 200222 Sept 2002
1/321/32 NLOM Nowcast SSH and Currents with Altimeter Tracks Overlaid NLOM Nowcast SSH and Currents with Altimeter Tracks Overlaid
Altimeter track data from ERS-2 (red), GFO (black), and JASON-1 (white) were assimilated daily using a 3-day data window and the model as a first guess
Altimeter tracks are overlaid with the most recent seven days as solid lines
Daily MODAS SST analyses are also assimilated
Atmospheric wind and thermal forcing is from FNMOC/NOGAPS
Composite of most recent data Composite of most recent data Oct 2-Oct 6 2002, most is from Oct 2-Oct 6 2002, most is from
Oct 6Oct 6
Comparison of Global NLOM and SeaWIFS Eddies in the Comparison of Global NLOM and SeaWIFS Eddies in the Arabian SeaArabian Sea
Adapted from Shriver et al. (2005, JMS accepted)Adapted from Shriver et al. (2005, JMS accepted)
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
Ocean color eddy ID#
A or C
1/32 NLOM
1/16 NLOM
1/32 NLOMn
no assim
Eddy center position error in km 1 C 18 35 NP 2 A 28 103 NP 3 A 58 44 NP 4 C 12 43 45 5 C 42 35 31 6 C 17 42 NP 7 C 79 53 NP 8 A 40 NP NP 9 C 39 NP NP
10 A 35 30 NP 11 C 22 * 42 12 C 30 30 NP 13 A 11 35 NP 14 A 33 36 30 15 C NP 55 47 16 C * 14 * 17 C 13 NP NP 18 A 51 18 44 19 C 23 NP 26 20 C 12 NP NP % of eddies present 90% 70% 35% Median eddy center position error in km 29 35.5 42 % of eddies with most accurate position 57.5% 27.5% 15%
NP = not present* = fused with another eddy
Composite of most recent data Composite of most recent data Oct 2-Oct 6 2002, most is from Oct 2-Oct 6 2002, most is from
Oct 6Oct 6
Comparison of Global NLOM and SeaWIFS Eddies in the Comparison of Global NLOM and SeaWIFS Eddies in the Arabian SeaArabian Sea
Ocean color eddy ID#
A or C
1/32 NLOM
1/16 NLOM
1/32 NLOMn
no assim
Eddy center position error in km 1 C 18 35 NP 2 A 28 103 NP 3 A 58 44 NP 4 C 12 43 45 5 C 42 35 31 6 C 17 42 NP 7 C 79 53 NP 8 A 40 NP NP 9 C 39 NP NP
10 A 35 30 NP 11 C 22 * 42 12 C 30 30 NP 13 A 11 35 NP 14 A 33 36 30 15 C NP 55 47 16 C * 14 * 17 C 13 NP NP 18 A 51 18 44 19 C 23 NP 26 20 C 12 NP NP % of small eddies present 80% 60% 50% Median small eddy center position error in km 22.5 32.5 42 % of small eddies with most accurate position 55% 25% 20%
Adapted from Shriver et al. (2005, JMS accepted)Adapted from Shriver et al. (2005, JMS accepted)
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
NP = not present* = fused with another eddy
~7 grid intervals was the minimum eddy diameter the models could realistically depict
1/8 NCOM 128 km or 1.15 at 20N 1/16 NLOM 56 km or .5 at 20N 1/32 NLOM 28 km or .25 at 20N
Thus, results pertain to eddies 1/4 and larger
The 1/32 NLOM was able to depict small eddies, 25-75 km in diameter, with ~70%
reliabilility - Over the entire 25-75 km range - Impact of altimeter data assimilation was clear - Model dynamical interpolation/forecast skill was essential
1/16 NLOM was successful for eddies > 50 km in diameter
ConclusionsConclusions
ImplicationsImplications
Demonstrated the ability to represent small eddies, 25-75 km by assimilation of altimeter data
- This was a surprising and unanticipated result This result has strong implications for nested fine resolution coastal region models Value of altimeter data for assimilation by coastal region models
- Essential to separate the steric and non-steric components of SSH, especially in shallow water
Use a barotropic model
Value of high resolution boundary conditions
With assimilation of With assimilation of ERS-2, GFO and JASON 1 ERS-2, GFO and JASON 1
altimeter SSH dataaltimeter SSH data
Composite of most Composite of most recent data recent data
Oct 2-Oct 6 2002, Oct 2-Oct 6 2002, most is from Oct 6most is from Oct 6
Comparison of 1/32Comparison of 1/32 Global NLOM and SeaWiFS in the Global NLOM and SeaWiFS in the Arabian SeaArabian Sea
SeaWiFS ocean colorSeaWiFS ocean color 1/32° NLOM1/32° NLOM
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E 56°E 58°E 60°E 62°E
Altimeter dataassimilated
2200 eeddddiieess aarree iiddeennttiiffiieedd oonn tthhee oocceeaann ccoolloorr mmaapp
1/ 32 NLOM
1/ 32 NLOM no
assim % of eddies present
90% 35% Median eddy center location error in km
29 42 % of eddies with
most accurate eddy center location 75% 20%
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in cm)(in cm)(in mg/m(in mg/m33))
1.0 1.6 2.5 4.0 0.6 0.4 0.3
atmospheric forcing from FNMOC/NOGAPSatmospheric forcing from FNMOC/NOGAPS
Oct 6 2002Oct 6 2002
Adapted from Shriver et al. (2005, JMS accepted)Adapted from Shriver et al. (2005, JMS accepted) http://www.ocean.nrlssc.navy.mil/global_nlomhttp://www.ocean.nrlssc.navy.mil/global_nlom
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
SeaWiFS ocean colorSeaWiFS ocean color
24°N
22°N
20°N
18°N
16°N
26°N
56°E 58°E 60°E 62°E
1
1014
5
1117
18
12134
6
3
9
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
Gulf of Gulf of OmanOman
ArabianArabianPeninsulaPeninsula
IranIran
15
19 16
28
7
20
(in mg/m(in mg/m33))1.0 1.6 2.5 4.00.60.40.3
Gulf of Oman
ArabianPeninsula
Iran
1
11
10
2
6
7
Adapted from Hurlburt et al. (NRL Review 2005, in press)Adapted from Hurlburt et al. (NRL Review 2005, in press)
Oce
an c
olor
ed
dy I
D #
1/32
NL
OM
1/16
NL
OM
1/8
NC
OM
32
1/8
NC
OM
16
1/32
NL
OM
n
Eddy center position error in km 1 18 35 124 93 NP 2 28 103 58 70 NP 3 12 44 8 37 45 4 42 35 74 81 31 5 17 42 20 27 NP 6 79 53 NP NP NP 7 40 NP NP NP NP 8 39 NP NP NP NP 9 35 30 NP NP NP 10 22 60 46 82 42 11 33 36 NP NP 30
Number of the ocean color eddies depicted 11 11 9 6 6 4
Times had most accurate position 6 2 1 0 2
Comparison of Global NLOM, NCOM and SeaWIFS Eddies in the Comparison of Global NLOM, NCOM and SeaWIFS Eddies in the Arabian SeaArabian Sea
NP = not present
Hawaiian Islands Subregion
19 Mar 2004
Assimilation of SSH data from 1 altimeter (Jason-1)
r = .30
5 Jun 2004
Assimilation of SSH data from 3 altimeters
(Envisat, GFO, Jason-1)
r = .94
1/32 global NLOM 1/16 global NLOM
(in cm)Adapted from Shriver et al. (2004, JMS submitted)
23N
22N
21N
20N
19N
18N
22N
21N
20N
19N
18N159W 158W 157W 156W 155W 154W 159W 158W 157W 156W 155W 154W
