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

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

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 on 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?

Argo Observations (Oct-Nov 2004) (a) Subsurface tracks (b) Float positions where (T,S) were measured 60 ° N 60 ° N 50 ° N 50 ° N 40 ° N 40 ° N 30 ° N 30 ° N 20 ° N 20 ° N 10 ° N 10 ° N 0 ° N 0 ° N (a) (b) 10 ° S 10 ° S 70 ° W 50 ° W 30 ° W 10 ° W 70 ° W 50 ° W 30 ° W 10 ° W

Circulations at 1000 m estimated from the original ARGO float tracks (bin method) April 2004 – April 2005 480 60 ° N 60 ° N 440 400 50 ° N 50 ° N 360 320 40 ° N 40 ° N 280 30 ° N 240 30 ° N 200 20 ° N 160 20 ° N 120 10 ° N 80 10 ° N 40 5 cm/s 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W 0 ° N 50 ° W 30 ° W 10 ° W 70 ° W It is difficult to use such noisy data into ocean numerical models.

Optimal Spectral Decomposition (OSD) Method S K ∑ ∑ = × ∇ + × ∇ Ψ ( , ) ( )[ ( )] ( )[ ( )] U x t a t k Z x b t k x now 0 s s 0 k k 0 = = s 1 k 1 M = + Φ ∑ T ( x ,t ) T ( ) x c ( , ) t z ( ) x now cl m m = m 1 Z s � Harmonic Functions

Basis Functions (Open Boundaries) (Chu et al., 2003 a,b JTECH)

Boundary Configuration � Basis Functions for OSD 60 ° N 50 ° N Γ 2 40 ° N Azores Islands 30 ° N Γ 1 20 ° N 10 ° N Γ 3 0 ° N / Γ 3 10 ° S 70 ° W 50 ° W 30 ° W 10 ° W

Basis Functions for Streamfunction Mode-1 and Mode-2 60 ° N 60 ° N 50 ° N 50 ° N 40 ° N 40 ° N 1.8 2 1 . 2.4 − 1 6 −2 . 0 30 ° N 30 ° N 3 3 . 6 20 ° N 20 ° N 1 10 ° N 10 ° N 2 3 4 0 ° N 0 ° N 5 6 10 ° S 10 ° S 50 ° W 30 ° W 10 ° W 50 ° W 30 ° W 10 ° W 70 ° W 70 ° W

Circulations at 1000 m (March 04 to May 05) Bin Method OSD 60 ° N 60 ° N 50 ° N 50 ° N 40 ° N 40 ° N 30 ° N 30 ° N 20 ° N 20 ° N 10 ° N 10 ° N 5 cm/s 5 cm/s 0 ° N 0 ° N 50 ° W 30 ° W 10 ° W 50 ° W 30 ° W 10 ° W 70 ° W 70 ° W

Baroclinic Rossby Waves in Tropical North Atlantic

Argo float tracks (with 300 days or longer drifting) at 1000 m and 1500 m (April 04-April 05) 30 ° N 20 ° N 10 ° N 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W

Correction of Upper Ocean Current Drifting Caused by Vertical Shear = − eff ˆ x x U t p p p p t p � ascending/descending time (~ 10 hrs) 0 1 ∫ = eff * ( ) z dz U U p 0 H 0 p H p − 0 ( z H ) p * = − − + U ( U U ) U surf now now 0 H p

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 11 o N −0.5 −0.25 −0.25 5 . 0 Apr. −0.75 0.75 −1 −0.5 −1.25 −1 0.25 Feb. 0 0 . 5 1.75 0.75 Dec. 5 2 −0.25 −1 . 1 1 0.5 −0.5 Oct. −0.75 0 −1.25 0 . 2 0 0 Aug. 5 1 . . 5 5 5 0 7 0 . 1 − 1 June −0.5 −1.25 1 (a) (b) 50 ° W 40 ° W 30 ° W 20 ° W 50 ° W 40 ° W 30 ° W 20 ° W Semi-Annual Annual

Time –Longitude Diagrams of temperature Along 11 o N −0.3 −0.2 3 0.25 0 Apr. . 0 0.1 Apr. 0.03 − − 0 . −0.09 0 0 5 1 . 0 . 0 0 0 . − 5 1 3 . 0 . 0 5 − 0.03 0 0 3 . 0 3 Feb. Feb. 0.1 0.09 −0.05 −0.09 0 0.03 − 0.1 0 . 0 −0.1 3 0.09 − Dec. Dec. 0 0 5 1 . 0.2 0 . 0 0.4 3 0 . 0 3 3 −0.1 0 0 . 3 . 0 1 − Oct. −0.3 Oct. . 0 0 9 0 −0.2 0 −0.03 . 0 − 0.03 0.03 −0.1 0.1 − 0.03 Aug. Aug. 0 −0.03 0.05 0.1 . 0 9 3 −0.1 0 . 0 −0.15 0 0 0 . 1 5 . −0.2 0.09 0 −0.03 0.05 9 June June −0.3 0 0.25 (c) (d) (a) (b) 50 ° W 40 ° W 30 ° W 20 ° W 50 ° W 40 ° W 30 ° W 20 ° W 50 ° W 40 ° W 30 ° W 20 ° W 50 ° W 40 ° W 30 ° W 20 ° W Semi-Annual Annual Annual Semi-Annual 950 m 550 m

Annual Currents (1000 m) Jul-Aug 2004 May-Jun 2004 30 ° N 30 ° N 5 cm/s 5 cm/s 20 ° N 20 ° N λ 1 // B 1 λ 2 A 1 10 ° N / B 1 10 ° N B 1 A 1 (b) (a) 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W Nov-Dec 2004 Sep-Oct 2004 30 ° N 30 ° N 5 cm/s 5 cm/s 20 ° N // 20 ° N B 1 A 1 B 2 10 ° N 10 ° N A 2 A 2 (d) (c) 0 ° N 0 ° N 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

Characteristics of Annual Rossby Waves Eastern Basin Western Basin Eastern Basin Western Basin

Annual Monthly Temperature Anomaly ( o C) at 950 m Depth � Annual Rossby Waves (7-10 cm/s) Jun 04 Aug 04 30 ° N 30 ° N 4000 1000 0 0 4000 0 1000 4000 0 20 ° N 4000 2000 20 ° N 0 0 2000 2000 2 0 0 0 10 ° N 1000 4000 10 ° N 3000 1000 4000 4000 3000 3000 4000 3000 (a) 0 0 (b) 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W Oct 04 Dec 04 30 ° N 30 ° N 4000 1000 0 0 1000 0 0 0 0 4 0 0 0 0 0 0 4 0 20 ° N 4 20 ° N 2000 2000 2000 2000 0 10 ° N 10 ° N 1000 1 0 0 0 0 0 0 0 0 0 4 4 3000 3 4000 4 0 0 0 3000 3 0 0 0 0 0 0 (d) (c) 0 0 ° N 0 ° N 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 −0.5 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 0.5 Temperature anomaly ( ° C)

Annual Monthly Temperature Anomaly ( o C) at 250 m Depth � Equatorially Forced Coastal Kelvin waves (27-30 cm/s) Jun 04 Aug 04 30 ° N 30 ° N 0 0 0 4000 0 0 0 0 1000 4 0 1 0 4000 0 0 4000 20 ° N 2000 20 ° N 2000 2000 0 2000 10 ° N 1000 4000 0 10 ° N 3000 4000 1000 4000 3000 3000 4000 3000 (b) 0 ° N (a) 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W 0 ° N 70 ° W 60 ° W 50 ° W 40 ° W 30 ° W 20 ° W 10 ° W Oct 04 Dec 04 30 ° N 30 ° N 4000 4000 1000 0 0 0 0 0 1 0 0 0 0 4000 0 0 4 20 ° N 20 ° N 2000 2000 2000 2000 0 0 10 ° N 10 ° N 1000 0 1000 4000 0 0 4 3000 4000 3000 4000 3000 3000 (c) (d) 0 ° N 0 ° N 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 −0.5 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 0.5 Temperature anomaly ( ° C)

Zonal cross-sections of the annual component of the temperature anomaly ( o C) 0 0.3 100 0.45 . 0.9 1 −0.15 200 300 −0.1 −0.05 0 Depth (m) 400 0.05 −0.15 500 −0.05 A 1 0 6 o N in Jun 04 � − 600 0 . 0 −0.15 5 700 800 (a) 900 45 ° W 40 ° W 35 ° W 30 ° W 25 ° W 20 ° W 15 ° W 0.3 0.1 100 −1.2 0 . 2 −1 −0.6 −0.3 200 0 0.1 −0.3 −0.1 −0.2 300 0 400 Depth (m) 11 o N in Oct, 04 � 500 A 1 0.3 600 −0.2 700 0.2 0 800 0.1 −0.1 (b) 900 0 50 ° W 45 ° W 40 ° W 35 ° W 30 ° W 25 ° W 20 ° W 0 100 −0.1 −0.2 − − 0.1 0 0 . 200 6 . 0 4 0 −0.2 300 −0.1 Depth (m) 400 −0.2 16 o N in Oct 04 � −0.3 500 A 1 0.2 0 1 600 − . 0 0 . 4 700 800 (c) 900 50 ° W 45 ° W 40 ° W 35 ° W 30 ° W 25 ° W 20 ° W

Baroclinic Modes 0 0 500 500 1000 1000 3 1500 1500 Depth (m) Depth (m) 1 2 2000 2000 2500 2500 3000 3000 3500 3500 (a) (b) 4000 4000 −1 0 1 −1 0 1 Φ l Φ l combination