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$BH/I=Wang Yafei (Professor, Chinese Academy of Meteorological Sciences)
$BBj!!L\!'(BThe relationship among the Okhotsk high, subtropical high,
East Asian monsoon and ENSO events

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The relationship among the Okhotsk high, subtropical high, East Asian monsoon and ENSO events(Wang Yafei) $BH/I=MW;](B :

  
  This seminar is about the relationship between the East Asian summer  
 monsoon and the El Nino Southern Oscillation (ENSO) during the period  
 from 1958 to 1998, which is quite different from the link between the  
 South Asian summer monsoon and ENSO.   
  
  Current findings are: (1) A new index, called the East Asian Monsoon Index  
 (EAMI), is defined for measuring the East Asian monsoon, which could  
 extensively describe the south-north distribution of the East Asian summer  
 monsoon's activity.  The interannual variability of the EAMI displays a  
 significant negative correlation with the broad-scale Asian monsoon index  
 proposed by Webster and Yang (1992) from 1976 to 1998.  (2) A significant  
 positive correlation between the summer 500 hPa geopotential height  
 anomalies and the NINO-3 SST in the preceding fall and winter is found in the  
 subtropical regions of East Asia and the western North Pacific, and in  
 northeast Asia centered at 70N, 137.5E.  A strong (weak) summer  
 monsoon in the subtropical regions of East Asia tends to occur about two to  
 three seasons after the NINO-3 SST anomalies exceed 1.5$B!k(BC (drop below  
 -0.7$B!k(BC).  (3) The above results suggest a delayed impact of the ENSO on the  
 East Asian summer atmosphere circulation.  During the summer after the El  
 Nino reaches its mature phase, an anomalous blocking anticyclone tends to  
 occur in northeast Asia.  Meanwhile a subtropical high of the western North  
 Pacific extends abnormally westward.  This anomalous circulation pattern  
 enhances the summer monsoon in subtropical East Asia.  The  
 abovementioned evolution of the circulation anomalies became more  
 prominent in the unprecedented '97/98 El Nino event, suggesting that the  
 devastating 1998 flood in southern central China may be partially due to the  
 delayed impact of the '97/98 El Nino. (4) Ending the argument if there is a  
 significant correlation between ENSO and East Asian monsoon 
  
   The physical processes for the delayed impact besides the air-sea  
 interaction in the tropical and subtropical western Pacific are discussed  
 too. 
  
   

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$BO"Mm@h(B

$B? $BBg5$3$MN7w4D6-2J3X@l96(B $BJ*M}7O(B
mail-to:yasuf@lowtem.hokudai.ac.jp / Tel: 011-706-7432