GFDL - Geophysical Fluid Dynamics Laboratory

Prediction of Summer Sea Surface Temperature Anomalies in the Eastern North Pacific Ocean

Prediction of Summer Sea Surface Temperature Anomalies in the Eastern North Pacific Ocean

Abstract: [from published manuscript]

A study of summer sea surface temperature anomalies in the eastern North Pacific Ocean was undertaken
to examine some of the processes that could affect their evolution and which may be important for their
prediction. An empirical approach was utilized. The factors considered include sea surface temperature (SST)
persistence (due to the relatively large heat capacity of the water), oceanic thermal advection, and wind
mixing (which presumably acts through changes in the mixed layer depth of the ocean). The primary variable
studied was the summer SST anomaly for each of 25, 5 deg latitude by 10 deg longitude boxes in the region
140W-170E, 30-55N. Thirty years of data were used (1947-76).

Diagnostic analyses using data from four Ocean Weather Stations (C, D, P and V) were performed prior to the
analyses described above in order to examine wind mixing more closely. Only at the OWS’s are high frequency
(3 hour), measured wind speeds available at the same location as SST observations for a long period of time.
These analyses indicated a statistically significant lag relationship between average April and May monthly
wind speed and subsequent summer SST at Station P.

The monthly mean SLP gradient was used as an estimate of average monthly wind speed over the 25 box
domain where measured winds are not routinely available. In addition, winds derived from daily sea level
pressure (SLP) analyses were averaged to form monthly means. At most boxes, no significant lag relationship
between summer SST anomalies and spring (April and May) winds was found using either data set.

The box-averaged data were employed to specify the summer SST from the components of the total horizontal
thermal advection (based on the mean and anomalous components of the surface current and SST fields). The
anomalous summer surface current advecting the mean summer SST field was found to be the dominant
horizontal advective term affecting the local time rate of change of SST, particularly for 40-50N. Substitution
of derived May anomalous currents for those of summer greatly diminished the strength of the relationship.

In the predictive portion of the study, skill relative to persistence was marginal based upon dependent sample
testing. Thus, in the predictive mode neither wind mixing (as parameterized here) nor oceanic thermal
advection added very much information not contained in the initial SST anomaly field. However, persistence
alone exhibited considerable skill, particularly in the northeastern portion of the domain.

Author:
Lanzante, John Robert

Publication Info:
1981

Physical descrip:
v, 63 leaves : ill., map ; 29 cm.

Dissertation note:
Thesis (M. Sc.)–Rutgers University, 1981.

Subject:
Ocean temperature–Pacific Ocean.

Added title:
Rutgers theses. Dept. of Meteorology, 1981.

Sub-Location:
R-THES

Call Numbers for: SPCOL/UA:
GC.L297 1981

URL:
http://www.iris.rutgers.edu/uhtbin/cgisirsi/H2qAp5xPqP/ALCOHOL/9690008/8/2089719/Lanzante,+John+Robert.