Re: SSH question

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Posted by Gang Yuan on January 25, 2000 at 13:06:27:

In Reply to: SSH question posted by Randy Watts on November 07, 2000 at 14:29:09:

: Gang et al. -- very nice poster!
: Would you explain more about a statement in your abstract:
: "...difference is assumed due to that acoustic tomography is able to
: measure both of the signals associated with the seasonal
: thermocline (sea surface layer) and permanent thermocline
: (subsurface layer) changes, but the altimeter could mainly pick up
: the signal associated with the variation occurred above the seasonal
: thermocline in the recirculation region."

: The SSH varies from internal density changes that affect
: dynamic height (baroclinic, BC), plus additional barotropic
: (BT) effects. Changes in dynamic height could come from within
: the permanent pycnocline as well as from the near-surface
: layer. So I expect the altimeter would detect variations
: equally well from the permanent thermocline AND from
: above the seasonal thermocline.
: --Randy
: contributions.

Dear Randy,

Please accept my apology for replying so late.

Thank you for your comment. Yes, you are right.
Since alimetry senses the ocean surface
heght (i.e., depth-integrated density), theoretically it can detect the variations from both the permanent thermocline AND the seasonal thermocline. But most part of these kind of SSH variations is due to the seasonal changes of steri
height (one-dimensional local forcing above the
seasonal thermocline. Dr. Stammer (Stammer, D. JGR
Vol. 102 NO. C9 p20987-21009, 1997) shown that after removing steric height from the altimeter T/P observations, the amplitude of the annual cycle drops on zonal average to very small (about 2cm) everywhere outside the tropics. So we mentioned that the altimeter could mainly pick up
^^^^^^^^^^^^^^
the signal associated with the variation occurred above the seasonal thermocline (sea surface layer). Thanks for your insightful question.
Also thank you for catching the label mistake.
I have checked my original figure, it was correct. So maybe this error was due to the picture format converting PS to GIF.

Thanks,

Gang

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Comments:
: : Gang et al. -- very nice poster! : : Would you explain more about a statement in your abstract: : : "...difference is assumed due to that acoustic tomography is able to : : measure both of the signals associated with the seasonal : : thermocline (sea surface layer) and permanent thermocline : : (subsurface layer) changes, but the altimeter could mainly pick up : : the signal associated with the variation occurred above the seasonal : : thermocline in the recirculation region." : : The SSH varies from internal density changes that affect : : dynamic height (baroclinic, BC), plus additional barotropic : : (BT) effects. Changes in dynamic height could come from within : : the permanent pycnocline as well as from the near-surface : : layer. So I expect the altimeter would detect variations : : equally well from the permanent thermocline AND from : : above the seasonal thermocline. : : --Randy : : contributions. : Dear Randy, : Please accept my apology for replying so late. : Thank you for your comment. Yes, you are right. : Since alimetry senses the ocean surface : heght (i.e., depth-integrated density), theoretically it can detect the variations from both the permanent thermocline AND the seasonal thermocline. But most part of these kind of SSH variations is due to the seasonal changes of steri : height (one-dimensional local forcing above the : seasonal thermocline. Dr. Stammer (Stammer, D. JGR : Vol. 102 NO. C9 p20987-21009, 1997) shown that after removing steric height from the altimeter T/P observations, the amplitude of the annual cycle drops on zonal average to very small (about 2cm) everywhere outside the tropics. So we mentioned that the altimeter could mainly pick up : ^^^^^^^^^^^^^^ : the signal associated with the variation occurred above the seasonal thermocline (sea surface layer). Thanks for your insightful question. : Also thank you for catching the label mistake. : I have checked my original figure, it was correct. So maybe this error was due to the picture format converting PS to GIF. : Thanks, : Gang

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