Jt. Allen et al., Diagnosis of vertical velocities with the QG omega equation: an examination of the errors due to sampling strategy, DEEP-SEA I, 48(2), 2001, pp. 315-346
Citations number
26
Categorie Soggetti
Aquatic Sciences","Earth Sciences
Journal title
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
Vertical motion at the mesoscale plays a key role in ocean circulation, oce
an-atmosphere interaction, and hence climate. It is not yet possible to mak
e direct Eulerian measurements of vertical velocities less than 1000 m day(
-1). However, by assuming quasi-geostrophic (QG) balance, vertical velociti
es O (10 m day(-1)) can be diagnosed from the geostrophic velocity field an
d suitable boundary conditions. Significant errors in the accuracy of this
diagnosis arise from the necessary compromise between spatial resolution an
d synopticity of a hydrographic survey. This problem has been addressed by
sampling the output of a numerical ocean model to simulate typical oceanogr
aphic surveys of mesoscale fronts. The balance between the number of observ
ations and the synopticity of observations affects the apparent flow and in
particular the diagnosed vertical motion. A combination of effects can typ
ically lead to errors of 85% in the estimation of net vertical heat flux. A
n analytical two-layer model is used to understand components of this error
and indicate the key parameters for the design of mesoscale sampling. (C)
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