Mid-Depth Rossby Wave Propagation in the Tropical North Atlantic - - PowerPoint PPT Presentation

Mid-Depth Rossby Wave Propagation in the Tropical North Atlantic Observed from Argo Floats

Peter C. Chu Naval Postgraduate School (NPS) Leonid Ivanov (NPS) Oleg Melnichenko (Univ of Hawaii) N.C. Wells (SOC, UK)

International Association of Physical Sciences of Oceans Montreal, Canada, 20-24 July 2009

References

• Chu, P.C., L.M. Ivanov, T.P. Korzhova, T.M. Margolina, and O.M. Melnichenko,

2003a: Analysis of sparse and noisy ocean current data using flow decomposition. Part 1: Theory. Journal of Atmospheric and Oceanic Technology, 20 (4), 478-491.

• Chu, P.C., L.M. Ivanov, T.P. Korzhova, T.M. Margolina, and O.M. Melnichenko,

2003b: Analysis of sparse and noisy ocean current data using flow decomposition. Part 2: Application to Eulerian and Lagrangian data. Journal of Atmospheric and Oceanic Technology, 20 (4), 492-512.

• Chu, P.C., L.M. Ivanov, and T.M. Margolina, 2004: Rotation method for

reconstructing process and field from imperfect data. International Journal of Bifurcation and Chaos, 14(8), 2991-2997.

• Chu, P.C., L.M. Ivanov, and O.M. Melnichenko, 2005: Fall-winter current reversals
• n the Texas-Lousiana continental shelf. Journal of Physical Oceanography, 35,

902-910

• Chu, P.C., L.M. Ivanov, O.M. Melnichenko, and N.C. Wells, 2007: On long

baroclinic Rossby Waves in the tropical North Atlantic observed from profiling

• floats. Journal of Geophysical Research – Oceans, in press.
• These papers can be downloaded from:
• http://www.oc.nps.navy.mil/~chu

Oceanic Rossby waves have been identify at the surface from satellite data

• SSH (TOPEX/Poseidon)
• SST
• Ocean Colors

Rossby waves identified from satellite SSH data in the South China Sea (Chu and Fang, 2003)

Rossby waves identified from satellite SST, ocean color data for the Indian Ocean (Subrahmanyan et al. 2009)

Can we detect the Rossby wave propagation at the mid-depth such as 1000 m depth?

70°W 50°W 30°W 10°W 10°S 0°N 10°N 20°N 30°N 40°N 50°N 60°N

(a)

70°W 50°W 30°W 10°W 10°S 0°N 10°N 20°N 30°N 40°N 50°N 60°N

(b)

Argo Observations (Oct-Nov 2004)

(a) Subsurface tracks (b) Float positions where (T,S) were measured

Circulations at 1000 m estimated from the original ARGO float tracks (bin method) April 2004 – April 2005

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N 40°N 50°N 60°N 40 80 120 160 200 240 280 320 360 400 440 480

70°W 50°W 30°W 10°W 10°N 20°N 30°N 40°N 50°N 60°N 0°N

5 cm/s

It is difficult to use such noisy data into ocean numerical models.

Optimal Spectral Decomposition (OSD) Method

)] ( )[ ( )] ( )[ ( ) , (

1 1

x k x k x U

∑ ∑

= =

∇ × + ∇ × =

K k k k s S s s now

t b Z t a t Ψ

1

( ) ( ) ( , ) ( )

M now cl m m m

T ,t T c t z

=

= + Φ ∑ x x x

Zs Harmonic Functions

Basis Functions (Open Boundaries)

(Chu et al., 2003 a,b JTECH)

70°W 50°W 30°W 10°W 10°S 0°N 10°N 20°N 30°N 40°N 50°N 60°N

Γ2 Γ3

/

Γ3 Γ1

Azores Islands

Boundary Configuration Basis Functions for OSD

. 6 1 . 2 1.8 2.4 3 3 . 6 70° W 50° W 30° W 10° W 10°S 0°N 10°N 20°N 30°N 40°N 50°N 60°N − 1 −2 1 2 3 4 5 6 70° W 50° W 30° W 10° W 10°S 0°N 10°N 20°N 30°N 40°N 50°N 60°N

Basis Functions for Streamfunction Mode-1 and Mode-2

70°W 50°W 30°W 10°W 10°N 20°N 30°N 40°N 50°N 60°N 0°N

5 cm/s

70°W 50°W 30°W 10°W 10°N 20°N 30°N 40°N 50°N 60°N 0°N

5 cm/s

Circulations at 1000 m (March 04 to May 05) Bin Method OSD

Baroclinic Rossby Waves in Tropical North Atlantic

10°W 20°W 30°W 40°W 50°W 60°W 70°W 0°N 10°N 20°N 30°N

Argo float tracks (with 300 days or longer drifting) at 1000 m and 1500 m (April 04-April 05)

Correction of Upper Ocean Current Drifting Caused by Vertical Shear

p eff p p p

t ˆ U x x − =

tp ascending/descending time (~ 10 hrs)

*

1 ( )

p

eff p p H

z dz H =

∫

U U

now p p now surf

H H z U U U U + − − − =

*

) ( ) (

Fourier Expansion Temporal Annual and Semi-annual

Fourier Expansion Temporal Annual and Semi-anuual

Optimization

Annual Component

Semi-annual Component

Time –Longitude Diagrams of Meridional Velocity Along 11oN

−1.25 − 1 . 7 5 −0.5 −1 −0.5 −1 −0.75 −0.25 1.75 1 . 2 5 . 2 5 0.75 1 . 5 1 . 5 0.5 −1.25 −0.75 −0.25 −1.25 −1 −0.5 −0.5 −0.25 1 . 5 1 . 5 0.25 0.75

June Aug. Oct. Dec. Feb. Apr. 50°W 40°W 30°W 20°W 50°W 40°W 30°W 20°W (a) (b)

Annual Semi-Annual

Time –Longitude Diagrams of temperature Along 11oN

Annual Semi-Annual

−0.1 −0.2 −0.3 −0.05 −0.1 −0.2 −0.3 − . 1 −0.2 −0.3 . 5 . 1 5 0.25 0.1 0.2 . 3 0.4 0.05 . 1 5 0.25 0.1 −0.1 −0.1 − . 5 . 1 0.1 0.1 0.1 0.05

June Aug. Oct. Dec. Feb. Apr. 50°W 40°W 30°W 20°W 50°W 40°W 30°W 20°W (a) (b)

− . 3 −0.09 −0.03 − . 9 −0.15 0.03 0.03 . 9 . 3 0.09 . 1 5 0.03 − . 3 −0.03 − . 3 −0.09 − . 3 − . 9 − . 3 −0.03 . 3 . 3 0.03 0.09 . 3 0.09 0.03 0.03

June Aug. Oct. Dec. Feb. Apr. 50°W 40°W 30°W 20°W 50°W 40°W 30°W 20°W (c) (d)

Annual Semi-Annual

550 m 950 m

Annual Currents (1000 m)

10°W 20°W 30°W 40°W 50°W 60°W 70°W 0°N 10°N 20°N 30°N

5 cm/s (a)

A1 B1 λ1 λ2

10°W 20°W 30°W 40°W 50°W 60°W 70°W 0°N 10°N 20°N 30°N

5 cm/s (b)

A1 B1

/

B1

//

10°W 20°W 30°W 40°W 50°W 60°W 70°W 0°N 10°N 20°N 30°N

5 cm/s (c)

B1

//

A1 A2

10°W 20°W 30°W 40°W 50°W 60°W 70°W 0°N 10°N 20°N 30°N

5 cm/s (d)

A2 B2

May-Jun 2004 Jul-Aug 2004 Sep-Oct 2004 Nov-Dec 2004

Characteristics of Annual Rossby Waves

Western Basin Eastern Basin Western Basin Eastern Basin

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(a)

4000 4000 4000 3000 4000 3000 1000 2000 2000 1000

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(b)

4000 4000 4000 3000 4000 3000 1000 2 2000 1000

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(c)

4 4 4 3 4 3 1 2000 2000 1000

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(d)

4000 4 4000 3000 4 3000 1000 2000 2000 1000

−0.5 −0.4 −0.3 −0.2 −0.1 0.1 0.2 0.3 0.4 0.5 Temperature anomaly (°C)

Annual Monthly Temperature Anomaly (oC) at 950 m Depth Annual Rossby Waves (7-10 cm/s)

Jun 04 Aug 04 Oct 04 Dec 04

−0.5 −0.4 −0.3 −0.2 −0.1 0.1 0.2 0.3 0.4 0.5 Temperature anomaly (°C)

Annual Monthly Temperature Anomaly (oC) at 250 m Depth Equatorially Forced Coastal Kelvin waves (27-30 cm/s)

Jun 04 Aug 04 Oct 04 Dec 04

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(a)

4000 4000 4000 3000 4000 3000 1000 2000 2000 1000

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(b)

4 1 4000 2000 3000 4000 3000 4000 2000 1000

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(c)

4000 4 4000 3000 4 3000 1000 2000 2000 1

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(d)

4000 4000 4000 3000 4000 3000 1000 2000 2000 1000

900 800 700 600 500 400 300 200 100 Depth (m) − . 5 −0.1 −0.15 −0.05 −0.05 −0.15 −0.15 0.05 0.9 . 1 0.45 0.3 45°W 40°W 35°W 30°W 25°W 20°W 15°W

(a)

900 800 700 600 500 400 300 200 100 −0.1 −0.2 −0.2 −0.3 −0.1 −0.3 −0.6 −1 −1.2 0.1 0.2 0.3 0.1 . 2 0.1 0.3 45°W 40°W 35°W 30°W 25°W 20°W

(b)

Depth (m) 50°W 900 800 700 600 500 400 300 200 100 − . 4 −0.3 −0.2 −0.1 −0.2 − . 4 − . 6 −0.1 −0.2 0.2 . 1 0.1

(c)

50°W 45°W 40°W 35°W 30°W 25°W 20°W Depth (m)

A1 A1 A1

Zonal cross-sections of the annual component of the temperature anomaly (oC)

6oN in Jun 04 11oN in Oct, 04 16oN in Oct 04

−1 1 4000 3500 3000 2500 2000 1500 1000 500 Depth (m) Φl −1 1 4000 3500 3000 2500 2000 1500 1000 500 Φl combination

(b) (a)

1 2 3 Depth (m)

Baroclinic Modes

IV VI VIII X XII II IV 1 2 3 <Ei> (m2/s2) IV VI VIII X XII II IV 0.5 1 <ei> (cm2/s2) IV VI VIII X XII II IV −0.4 −0.2 0.2 0.4 0.6 0.8 Rii IV VI VIII X XII II IV −0.5 0.5 1 Month R11 0.2 0.4 0.6 0.8

(a) (c) (b)

R11(δt) ∧ ∧

(d)

Annual Component in the Western Sub-Basin

Mean wind KE Mean KE for mid-depth currents Correlation between Winds and currents

Correlation between wind Stress curl and streamfunction (solid: no-lag, dashed: 3 mon lag

Zonal: circle Meridional: square

Annual Component in the Eastern Sub-Basin

Mean wind KE Mean KE for mid-depth currents Correlation between Winds and currents

Correlation between wind Stress curl and streamfunction (solid: no-lag, dashed: 3 mon lag

Zonal: circle Meridional: square

IV VI VIII X XII II IV 2 4 6 <Ei> (m2/s2) IV VI VIII X XII II IV 0.5 1 1.5 2 <ei> (cm2/s2) IV VI VIII X XII II IV 0.2 0.4 0.6 0.8 1 Rii IV VI VIII X XII II IV 0.2 0.4 0.6 0.8 Month R11 −0.5 0.5

(a) (c) (b)

R11(δt) ∧ ∧

(d)

(a)

0°N 10°N 20°N 30°N

5 cm/s

70°W 60°W 50°W 40°W 30°W 20°W 10°W 70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

5 cm/s (b)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(c) 5 cm/s

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

5 cm/s (d)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(e) 5 cm/s

D1 C2 C1 D2 C2 C1 D3 D4 D2 D1 C2 D3 D4 C1 D2 D1 C2 C1 D2 D3 D4 D1 C2 C1 D2 D1 D4

Semi-annual currents at 1000 m depth (2004)

(a)5/15 (b)5/30 (c)6/14 (d)6/29 (e) 7/13

Semi-annual monthly temperature anomaly at 950m depth

(a)Jun 04 (b) Aug 04 (c) Oct 04 (d) Dec 04.

−0.5 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 0.5 70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(a)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(b)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(c)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(d)

Temperature anomaly (°C)

800 600 400 200 Depth (m) − . 5 −0.1 −0.1 −0.2 −0.3 −0.05 −0.2 0.05 0.15 0.25 . 3 5 0.05 . 5 0.1 0.1 . 2 . 3 5 0.45 55°W 50°W 45°W 40°W 35°W 30°W 25°W 20°W

(a)

800 600 400 200 Depth (m) −0.05 −0.1 − . 1 5 −0.15 − . 2 5 −0.05 −0.1 0.05 0.1 0.15 0.15 . 2 5 0.05 0.1 . 1 5 55°W 50°W 45°W 40°W 35°W 30°W 25°W 20°W

(b)

800 600 400 200 Depth (m) −0.05 −0.15 −0.25 − . 3 5 −0.45 −0.55 −0.05 − . 1 5 −0.05 −0.15 − . 2 5 . 5 0.1 0.1 . 5 0.15 0.05 . 1 5 . 5 0.2 55°W 50°W 45°W 40°W 35°W 30°W 25°W 20°W

(c)

800 600 400 200 Depth (m) −0.05 −0.1 − . 1 5 − . 2 −0.25 −0.3 −0.05 −0.1 −0.05 −0.05 − . 1 −0.2 −0.3 −0.4 −0.5 . 5 0.1 . 1 0.15 . 2 5 . 5 0.15 55°W 50°W 45°W 40°W 35°W 30°W 25°W 20°W

(d)

Semi-annual component of monthly temperature anomaly along 11oN (2004)

(a) 6/4 (b) 7/4 (c) 8/4 (d) 9/4

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(a)

70°W 60°W 50°W 40°W 30°W 20°W 10°W 0°N 10°N 20°N 30°N

(b)

−0.5 −0.4 −0.3 −0.2 −0.1 0.1 0.2 0.3 0.4 Temperature anomaly (°C)

Semi-annual temperature anomaly at 550m depth (2004) (a) 5/15 (b) 6/29

IV VI VIII X XII II IV 0.5 1 1.5 2 2.5 <Ei> (m2/s2) IV VI VIII X XII II IV 0.1 0.2 0.3 0.4 <ei> (cm2/s2) IV VI VIII X XII II IV −0.4 −0.2 0.2 Rii Month IV VI VIII X XII II IV −0.6 −0.4 −0.2 0.2 0.4 0.6 rii IV VI VIII X XII II IV −0.8 −0.6 −0.4 −0.2 0.2 0.4 0.6 0.8 Month rii

(a) (c) (b) ∼ ∼ ∼ (d) (e) ∼

__

Semiannual Component in the Western Sub-Basin

(a) wind KE (b) current KE (c) corr wind stress and currents (d) corr between semi-annual currents and annual mean wind (e) corr between semiannual currents and annual wind stress.

Semiannual Component in the Eastern Sub-Basin

(a) wind KE (b) current KE (c) corr wind stress and currents (d) corr between semi-annual currents and annual mean wind (e) corr between semiannual currents and annual wind stress.

IV VI VIII X XII II IV −0.6 −0.4 −0.2 0.2 0.4 0.6 Rii Month IV VI VIII X XII II IV 0.2 0.4 0.6 0.8 1 <ei> (cm2/s2) IV VI VIII X XII II IV 0.2 0.4 0.6 0.8 <Ei> (m2/s2) IV VI VIII X XII II IV −0.8 −0.4 0.4 0.8 rii IV VI VIII X XII II IV −0.8 −0.4 0.4 0.8 Month rii

(a) (c) (b) ∼ ∼ ∼ (d) (e) ∼

__

Results

• Mid-depth Rossby waves are identified using the

Argo data.

• The annual and semi-annual Rossby waves are

detected in both the western and eastern sub- basins.

• The wind-driven Ekman pumping seems to be

responsible for the Rossby wave generation in both the sub-basins.