Paper 2 



sect 



and 



t he 



over 



move 



re tu 



with 



the 



y i t h 



weak 



more 



lack 



arct 



Litt 



or S/ 



St ro 



I ow 



A La 



d w 

 rned 



a 



700 



pa 

 en in 



sou 



of 

 i c a 

 Le s 



the product of coupling between 



ng subtropical highs over each ocean 



height anomaly centers maintained t 



ska and southern Greenland/ their 



estward to mid-ocean from the co 



to more southern latitudes. These 



weakening of the Atlantic ridge fr 



mb Ipvel in winter to +15 ft (+46 m 



rtial filling of the Greenland lo 



g of polar westerlies and a shift of 



thern path. Once agairi/' as Wagner ( 



amplitude in the troughs at nid-l 



ir was largely contained at high lat 



outhward penetration over North Amer 



1 nt en 



Wh 



heir 



corr e 



nt i ne 



mov 



om +3 



) in 



w/ ef 



thei 



1977) 



at i t u 



i tude 



i ca . 



se subpolar lows 

 ile^ on averager 

 winter positions 

 spending ridges 

 nt a I margins and 

 ements /^ coup led 

 10 ft (+95 m) at 

 spring^ along 

 fected a general 

 r main axis to a 

 po i nt s out r the 

 des meant that 

 s in spring with 



It should be 

 implied in 

 f I ow within 

 March when 

 attain ed the 

 on av er age ; 

 obse rv ed at 

 Lakes to I 

 However/' alt 

 cont i nued t 

 injections o 

 centers of 

 "700 mb c i r cu 

 Atlantic^ a 

 aver ag ed for 

 1977). Fla 

 ch arac te ri ze 

 In the Pac 

 subtropi cal 

 easterly f I 

 s t rong t y pho 



noted/ however/ that the general westerly vigor 

 Figure 2.3 conceals certain periods of more amplifiea 

 the season. The flow was certainly fast and zonal in 



the temperate westerlies over the Western Hemisphere 

 ir highest ^iarch value since records began (12.3 m/s 

 Taubensee 1976b). (*^ean anomalies of +5 m/s were 

 7G0 mb along the orincipal wind axis from the Great 

 celand/ with a +12 m/s anomaly south of Greenland, 

 hough vigorous upper westerlies (+9 m/s anomaly) 

 o be generated over the Pacific in April (where 

 f arctic and subtropical air around the principal 

 action were generating a strong baroclinic zone)/ the 

 lation amplified greatly over North America ana the 

 nd upper wind speeds were slightly below normal when 



the Western Hemisphere as a whole (Wagner 1976b/ 

 t/ faster than normal flow returned/ however/ to 



both ocean areas for the remainder of the spring, 

 ific sector the continued presence of an intense 

 ridge at higher latitudes than normal/ and the strong 

 ow to its south/ gave the stimulus for unusually 

 on activity over the southwest Pacific. 



These developments once again were reflected in the distri- 

 butions of surface temperature anomaly in spring over the eastern 

 Pacific and western Atlantic (Fig. 2.3). With much continuity in 

 the tendency of the circulation from winter to sprino/ the season 

 to season changes in sea surface temperature (SST) anomaly are 

 mainly those of detail. The northern Pacific continueo to oe 

 predominantly cold unoer its mean trough/ although the center of 

 cooling C-2.2F (-1.2C) anomaly in the seasonal mean] was situated 

 close to the Aleutians. To the south of this cold zone an 

 expanding belt of warm surface water marked the clear skies/ dry 

 settling air/ and oceanic convergence associated with the intense 

 subtropical ridge in its new mid-ocean location. Unoer its 

 eastern flank/ surface warming spread eastjaro toward the 

 American western seaboard/ continuing the erosion of the cold 



22 



