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第 62 回 大気海洋物理系 B 棟コロキウム のおしらせ

日 時:2000年 3月 22日(水) 午後 16:30 〜 18:30
場 所:地球環境科学研究科 A棟 803A

発表者:Erwin Mulyana (気候モデリング講座 M1)
題 目:論文紹介:An Assessment of the NCEP, NASA, and ECMWF Reanalis over the Tropical West Pacific Warm Pool.

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論文紹介:An Assessment of the NCEP, NASA, and ECMWF Reanalis over the Tropical West Pacific Warm Pool. (Erwin Mulyana) 発表要旨 :

 Three very different views of the mean structure and variability of 
 deep convection over the tropical east Indian and west Pacific Ocean, 
 provided by three different reanalysis datasets for 1980-93, are 
 highlighted. The datasets were generated at the National Centers for 
 Environmental Prediction, the National Aeronautics and Space 
 Administration's  Goddard Laboratory for Atmospheres, and the European  
 Centre  for Medium-Range Weather Forecasts (ECMWF). Precipitation, 
 outgoing  longwave radiation (OLR), and 200-mb wind divergence fields 
 from   the thee datasets are compared with one another and with 
 satellite  observations. Climatological means as well as interannual 
 and  intraseasonal (30-70 day) variability are discussed. For brevity  
 the  focus is restricted to northern winter (DJF). 
  
 The internal consistency of the datasets is high, in the sense that 
 geographical extremes of rainfall, OLR, and divergence in each dataset 
 correspond closely to one another. On the other hand, the external 
 consistency, that is, the agreement between the datasets, is so  low 
 as to defy a simple summary. Indeed, the differences are such as to 
 raise fundamental questions conserning 1) whether there is a single 
 or a split ITCZ over the west Pacific Ocean with a strong northern 
 branch, 2) whether there is more convection to the west or the  east 
 of Sumatera over the equatorial Indian Ocean, and 3) whether  there is 
 a relative minimum of convection near New Guinea. Geographical maps of 
 interannual and intraseasonal variances also show  similar order 1 
 uncertainties, as do regression against the principal  component time 
 series of the Madden-Julian oscillation. The annual cycle of 
 convection is also different in each reanalysis. Overall, the ECMWF 
 reanalysis compares best with observations in this region,  but it too 
 has important errors.  
 Finally, it is noted that although 200-mb divergence fields in the 
 three datasets are highly inconsistent with one another, the 200-mb 
 vorticity fields are highly consistent. This reaffirms the relevance 
 of diagnosing divergence from knowledge of the vorticity using the 
 method described in Sardeshmukh (1993). This would yield divergence 
 fields from the three datasets that are not only more consistent with 
 each other, but also more consistent with the 200-mb vorticity 
 balance. Further, as proxies of deep convection, they would help 
 resolve many of the issues raised above. 
  
  
 Matthew Newman at.all., Bulletin of the American Meteorological 
 Society, Vol.81, No.1, January 2000. 
  

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連絡先

伊藤 頼 / 谷口 博 @北海道大学大学院地球環境科学研究科
大気海洋圏環境科学専攻大循環 / 気候モデリング講座
mail-to:yori@ees.hokudai.ac.jp / Tel: 011-706-2357