Eddy diffusivity is a statistic that provides a quantitative measure of the 
diffusive transport caused by mesoscale motions.  The principal objective of 
this study is to estimate eddy diffusivities of the surface velocity field 
in the tropical Pacific Ocean.  The observations are satellite-tracked 
drifting buoys spanning the years 1979 through mid-1996.  The data were 
assembled and distributed by the data acquisition center at the NOAA 
Atlantic Oceanographic and Meteorological Laboratory (AOML) and were obtained 
as part of the Equatorial Pacific Ocean Climate Study (EPOCS) and World 
Ocean Circulation Experiment--Tropical Ocean-Global Atmosphere (WOCE-TOGA) 
programs.  The tropical Pacific surface current system is characterized 
by:  1) nonstationarity due to rapid response time of equatorial and 
near-equatorial dynamics; 2) strong meridional shear in the large-scale 
mean; and 3) an energetic mesoscale velocity component.  Taylor (1921) 
defined eddy diffusivity as the integral of the autocovariance of Lagrangian 
eddy velocities -- requiring both stationary and homogeneous statistics of 
the eddy field.  Eddy velocities were obtained in this study by removing 
the splined mean field to eliminate mean shear as described in Part 1 
(Bauer, et al 1998) and binned spatially to group data that have similar 
dispersion characteristics.  Temporal partitions were made to create 
stationary eddy statistics.  

Zonal diffusivity estimates vary with latitude from about 5x107 to 
76x107 cm2/s.  Largest estimates are in regions of strong meridional 
shear and large eddy variance between 4°S and 10°N.  However, 
meridional diffusivity estimates are nearly constant throughout the tropics 
varying from 2x107 to 9x107 cm2/s.  Simple autoregressive models 
provide the analysis with estimates of Lagrangian integral time scale which 
is a measure of the turbulence decorrelation time scale.  First order (AR(1)) 
and second order (AR(2)) autoregressive processes adequately describe the 
eddy transport statistics.  All zonal eddy transport statistics and 
meridional statistics from low variance regions (generally poleward of 
4°S and 10°N) can be modeled by AR(1) statistics modified by inertial 
wave oscillations. Meridional statistics of the near-equatorial regions 
(between 4°S and 10°N) are characterized by large meridional eddy 
variance associated in part with tropical instability waves (TIW's), 
and by low meridional diffusivity:  Wave motion increases eddy variance 
but does not diffuse water parcels with periodic trajectory motion.  
Therefore, meridional eddy diffusivities are low in these regions and are 
modeled by AR(2) statistics. 

An independent confirmation of the diffusivity estimates in the central 
and eastern  Pacific was obtained by comparing tracer flux divergence 
computed from a parameterization using  diffusivity estimates of our 
analysis and that from direct eddy Reynolds stress flux divergence.   Our 
results show that diffusivity can be estimated for regions that have not 
been considered before because of lack of data and because of the 
complexities of the velocity field.