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�� 90 �� �絤���η�ʪ���ϥ��ߥʡ� �Τ����餻

��������2000ǯ 11�� 30��(��) ���� 9:30 �� 12:00
�졡�ꡧ�ϵ�Ķ��ʳظ���� 2F��Ʋ

ȯɽ�ԡ�W.R. Young (Scripps Institution of Oceanography)
�ꡡ�ܡ�Temperature and salinity compensation in the ocean mixed layer

ȯɽ�ԡ�P. Cessi (Scripps Institution of Oceanography)
�ꡡ�ܡ�Low-frequency variability in simple models of ocean/atmosphere

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Temperature and salinity compensation in the ocean mixed layer (W.R. Young) ȯɽ�׻� :

  
 Recent high resolution measurements of temperature (T) and 
 salinity (S) in the northeast Pacific show that in the mixed layer 
 these two components virtually cancel in their joint effect on 
 density. This density compensation is observed on horizontal 
 length scales between 20 meters and 10 kilometers. Below the mixed 
 layer, in the thermocline, there is only partial compensation 
 between T and S gradients. I will argue that compensation can 
 be explained by density-driven shear dispersion: random 
 thermohaline forcing creates non-compensated T-S gradients, but 
 then the resulting density gradients drive vertically sheared 
 currents. The transport associated with these currents then 
 quickly remove the density gradients. This dynamics 
 suggests a diffusive parameterization in which the flux of T and S 
 is in the direction of the density gradient, and proportional to 
 the third power of the gradient. I will discuss model results 
 using this nonlinear parameterization. 
  

Low-frequency variability in simple models of ocean/atmosphere (P. Cessi) ȯɽ�׻� :

  
  A model of the large scale interaction between the troposphere and 
 the upper ocean, wind-driven circulation is formulated. Simplified 
 parametrizations, built upon the conservation of global heat and 
 momentum, relate the atmospheric eddy heat and momentum fluxes to the 
 zonally averaged oceanic and atmospheric temperatures. The formulation 
 shows that the wind-driven circulation influences the winds by 
 controlling the strength of the oceanic northward heat transport, and 
 thus the atmospheric northward heat transport and temperature 
 distribution. Because the ocean takes decades to adjust to changes in 
 the winds, the coupled system equilibrates into a state which is 
 periodic in time, rather than steady. The period is linearly 
 proportional to the transit time of long Rossby waves across the 
 basin, and thus is of the order of decades for large scale basins. 
  

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