Influence of a Southern Shift of the ITCZ from
Quick Scatterometer Data on the Pacific
North Equatorial Countercurrent |
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| Authors: | WU Fanghu LIN Pengfei and LIU Hailong |
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| Institution: | Division of Climate System Modeling, National Climate Center, Beijing 100081,
State Key of Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,
State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | By analyzing the climatologically averaged wind stress during 2000--2007, it
is found that the easterly wind stress in the northern tropical Pacific
Ocean from Quick Scatterometer (QSCAT) data was stronger than those from
Tropical Atmosphere Ocean (TAO) data and from National Centers for
Environmental Prediction/National Center for Atmospheric Research
(NCEP/NCAR) reanalysis I. As a result, the Intertropical Convergence Zone
(ITCZ) in the Pacific Ocean is more southward in the QSCAT data than in the
NCEP/NCAR data. Relative to the NCEP wind, the southern shift of the ITCZ in
the QSCAT data led to negative anomaly of wind stress curl north of a
latitude of 6oN. The negative anomaly results in downward Ekman pumping
in the central Pacific. The excessive local strong easterly wind also
contributes to the downward Ekman pumping. This downward Ekman pumping
suppresses the thermocline ridge, reduces the meridional thermocline slope
and weakens the North Equatorial Countercurrent (NECC). These effects were
confirmed by numerical experiments using two independent ocean general
circulation models (OGCMs). Furthermore, the excessive equatorial easterly
wind stress was also found to contribute to the weaker NECC in the OGCMs. A
comparison between the simulations and observation data indicates that the
stronger zonal wind stress and its southern shift of QSCAT data in the ITCZ
region yield the maximum strength of the simulated NECC only 33% of the
magnitude derived from observation data and even led to a ``missing" NECC
in the western Pacific. |
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| Keywords: | QuikSCAT wind stress NECC ocean model ITCZ |
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