A modified method to estimate eddy diffusivity in the North Pacific using altimeter eddy statistics  

作　　者：张志伟 李亚汝 田纪伟 

机构地区：[1]Key Laboratory of Physical Oceanography (Ocean University of China),Ministry of Education [2]School of Engineering,University of Liverpool

出　　处：《Chinese Journal of Oceanology and Limnology》2013年第4期925-933,共9页中国海洋湖沼学报（英文版）

基　　金：Supported by the Major Program of the National Natural Science Foundation of China (No.40890153);the National High Technology Research and Development Program of China (863 Program) (No.2008AA09A402)

摘　　要：The method proposed by Stammer (1998) is modified using eddy statistics from altimeter observation to obtain more realistic eddy diffusivity (K) for the North Pacific. Compared with original estimates, the modified K has remarkably reduced values in the Kuroshio Extension (KE) and North Equatorial Counter Current (NECC) regions, but slightly enhanced values in the Subtropical Counter Current (STCC) region. In strong eastward flow areas like the KE and NECC, owing to a large difference between mean flow velocity and propagation velocity of mesoscale eddies, tracers inside the mesoscale eddies are transported outside rapidly by advection, and mixing length L is hence strongly suppressed. The low eddy probability (P) is also responsible for the reduced K in the NECC area. In the STCC region, however, L is mildly suppressed and P is very high, so K there is enhanced. The zonally-averaged K has two peaks with comparable magnitudes, in the latitude bands of the STCC and KE. In the core of KE, because of the reduced values of P and L, the zonally-averaged K is a minimum. Zonally-integrated eddy heat transport in the KE band, calculated based on the modified K, is much closer to the results of previous independent research, indicating the robustness of our modified K. The map of modified K provides useful information for modeling studies in the North Pacific.The method proposed by Stammer （1998） is modified using eddy statistics from altimeter observation to obtain more realistic eddy diffusivity （K） for the North Pacific. Compared with original estimates, the modified K has remarkably reduced values in the Kuroshio Extension （KE） and North Equatorial Counter Current （NECC） regions, but slightly enhanced values in the Subtropical Counter Current （STCC） region. In strong eastward flow areas like the KE and NECC, owing to a large difference between mean flow velocity and propagation velocity of mesoscale eddies, tracers inside the mesoscale eddies are transported outside rapidly by advection, and mixing length L is hence strongly suppressed. The low eddy probability （P） is also responsible for the reduced K in the NECC area. In the STCC region, however, L is mildly suppressed and P is very high, so K there is enhanced. The zonally-averaged K has two peaks with comparable magnitudes, in the latitude bands of the STCC and KE. In the core of KE, because of the reduced values of P and L, the zonally-averaged K is a minimum. Zonally-integrated eddy heat transport in the KE band, calculated based on the modified K, is much closer to the results of previous independent research, indicating the robustness of our modified K. The map of modified K provides useful information for modeling studies in the North Pacific.

关 键 词：eddy diffusivity mesoscale eddy North Pacific 

分 类 号：P732[天文地球—海洋科学]