Low frequency variability of the CCS: effect of the 1997-98 El Nino.

X. Capet, J McWilliams, A. Shchepetkin (UCLA)

Eastern Pacific Ocean Conference 2004

Modeling strategy.

½ degree ROMS Pacific between 1970 and 1999. NCEP monthly forcings.

15km ROMS USWC between 1990 and 1999. Adjusted NCEP monthly forcings.

Offline coupling. Boundary

conditions updated every 10 days.

Pacific solution

TOPEX SSH anomaly 11/97-2/98 ROMS Pacific (0.5° grid)

ENSO simulations (0.5 degrees horizontal resolution)

Sea Surface Elevation between 1995 and 1999.

Boundary conditions between Sep.97 and Apr. 98 (SST and v anomalies).

Sep. Oct. Nov. Dec.Sep. Jan. Feb. Mar.

Wind climatology.

NCEPQuikSCAT

Wind climatology. Temperature along CalCOFI line 67

winter spring summer fall

Wind variability : longshore wind stress over the nearshore region

exp0>exp1

Experiment exp0: full variability

SSH anomaly exp0

Pt. Conception

C. Mendocino

May 97

Sep 97

Oct 97

Nov 97

Dec 97

Jan 98

Feb 98

Mar98

Apr 98

Jun 97

Temperature anomaly exp0

Wind Sensitivity: role of wind anomalies during El Nino 97-98.

Differences are minor everywhere expect

north of 40N at the onset and retreat of El

Nino conditions.

SSH anomaly exp0 SSH anomaly exp1

Temperature anomalies along the USWCOct 97

Nov 97

Dec 97

Jan 98

Feb 98

Mar98

Apr 98

Jun 97

1- The wind anomaly has a minor influence in the onset and further development of the model 97-98 ElNino

2- The most noticeable influence of wind anomaly is north of 40°N.

3- The ocean temperature signal seems to respond to wind changes rather than absolute values.

Wind Sensitivity: role of wind anomalies during the 97-98 El Nino

Origin of temperature anomalies and water displacement associated with the model 97-98 ElNino signal

Nov 97 Dec 97

Spiciness at 50 m depth

Jan 98 Feb 98

Spiciness at 70 m depth Jan 98

Lagrangian Trajectories

3D trajectories of floats released at 50m depth 30 km offshore between 30 and 42 degrees in mid october 1997

1996

Lagrangian Trajectories

Latitude as a function of time (oct 15 to dec15) for the floats released at 50m depth