A Global Comparison of Ekman Pumping From Satellite Scatterometers and
Ocean Data Assimilation Estimates

Paulo Polito^1, Tong Lee^2, and Ichiro Fukumori^2
1. Inst. Nac. de Pesquisas Espaciais, Sao Paulo, Brazil
2. Jet Propulsion Laboratory, California Institute of Technology

Ekman pumping, a form of wind-driven upwelling, plays important
roles in upper-ocean dynamics, thermodynamics, and biology as well as
in boundary-layer meteorology.  Inverse models, such as those of
ECCO (Estimation of the Circulation and Climate of the Ocean, 
http://www.ecco-group.org/), estimate wind forcing through
ocean data assimilation.  Scatterometer data provide a stringent test
of the skill of the assimilation in estimating wind.  Ekman pumping  
obtained from various scaterometers are compared with those 
derived from ECCO model which assimilate TOPEX-derived sea level
anomalies using the adjoint and Kalman filter/smoother methods. 
Differences in Ekman pumping between scatterometer and assimilation
estimates are quantified in terms of the mean, standard deviation, and
correlation.  Change in Ekman pumping due to the assimilation is
analyzed to identify the spectral (frequency-wavelength) space over
which the assimilation has significant impact.  The comparison also
highlights aspects where the ECCO model and assimilation schemes need
improvement.