SPACE SCALES OF SEA-SURFACE TEMPERATURE PATTERNS AND 



THEIR CAUSES 



Jerome Namias' 



ABSTRACT 



The space scales of monthly mean sea-surface-temperature (SST) anomalies over the 

 North Pacific are determined from data gathered over a 20-year period and analyzed 

 with the help of correlation fields. The characteristic scales are ascribed to complex 

 coupling between the atmosphere and ocean — specifically to long waves in the upper 

 westerlies and latitudinal variations in the westerlies, both of which produce anomalous 

 oceanic advection and heat exchange. The coherence of mid-tropospheric (700-mb) 

 heights, the cross-correlations between these and SST values, plus atmospheric "tele- 

 connections" (long distance relationships) implicit in these upper-level flow patterns 

 reveal the character of coupling. 



At the historic 1958 CalCOFI meetings at 

 Rancho Santa Fe the central theme was the 

 large-scale climatic warming of the North and 

 equatorial Pacific which had evolved over a few 

 years preceding the conference (Sette and 

 Isaacs, 1960). Elton Sette, who co-chaired this 

 meeting, stimulated much discussion of the time 

 and space scales of this warming. In his work 

 over subsequent years he has m.ade numerous 

 major contributions to the subject of large-scale 

 oceanic temperature patterns. It is the purpose 

 of this note to bring to light some new data and 

 ideas relevant to these problems and thus serve 

 both as a testimonial to Elton's work and as an 

 expression of gratitude for his unceasing en- 

 couragement to those of us working along similar 

 lines. 



The source of data for the present work is a 

 series of monthly mean sea-surface temperatures 

 (SST) extending from 1947 to 1966 generated 

 at the Scripps Institution of Oceanography from 

 files of about 8,000,000 ship reports which were 

 compiled by the National Marine Fisheries Ser- 

 vice from the National Weather Service reports. 

 Monthly averages of 2° geographic squares were 

 computed and then further averaged around 5° 



' Scripps Institution of Oceanography, University of 

 California, San Diego, La JoUa. CA 92037. 



Manuscript accepted October 1971. 

 FISHERY BULLETIN: VOL. 70, NO. 3, 



1972. 



intersections for areas north of lat 20°N. A 20- 

 year average for each month was then computed. 

 Departures of the monthly means from the 20- 

 year averages were used in the work described 

 below along with 700-mb heights obtained di- 

 rectly from the National Weather Service. 



To determine the coherence of North Pacific 

 SST patterns and possible teleconnections be- 

 tween them I have correlated the SST deviations 

 from the 20-year mean at one point with de- 

 viations of the other 154 points used in the 5° 

 oceanic grid for each of the winter months (De- 

 cember, January, and February) over the 20- 

 year period making a set of 60 values for each 

 point. Examples are shown in the middle charts 

 of Figures 1, 2, and 3. A similar procedure was 

 used with the atmospheric 700-mb heights as 

 shown in the upper charts of these figures. Fi- 

 nally, cross-correlation fields were prepared re- 

 lating SST point values to the 700 mb-height val- 

 ues elsewhere as shown in the lower charts. 

 The latter two sets of charts involving atmos- 

 pheric parameters were constructed to help ex- 

 plain the physical nature of the large-scale air- 

 sea coupling which accounts for the observed 

 scale of the predominant SST patterns. 



Before discussing these charts, I should men- 

 tion that the 700-mb level rather than sea level 



611 



