92 
Di. hydrogr. Z.40, 1987. H.3. Klein . Benthic storms 
with friction velocity «* = (l/30)t7and U the geostrophic velocity outside the BBL (Arm i 
and Millard [1976]). 
Five current meters, with 2 velocity components each, supply a total of 10 informations. 
Therefore, a streamfunction i/'can be approximated by a cubic polynomia 
'!> = 
7+(l « ! 
with a and v the coordinates of the current meters With positions related to the centre of 
the gravity system 
J= 7/2 A ’ :=t) at,d i*jr2* :=0 
V « I / = 1 
and n the number of current meters, the equation reads shorter. The coefficients arc 
fitted to the measurements by the method of least square sums. i. c. 
^ CO/-', - v,) 2 4- {i/j t + h) 2 ) = rninimumffl,,,). 
i * I 
and with u and i the \elocity components in cast-west and north-south direction respcctivc- 
1\. The introduction of a horizontal streamfunction ip, respectively the neglect of the vertical 
velocity component, is reasonable because the latter is about 2 to 3 orders of magnitude 
smaller than the horizontal velocity, i e. in the order of magnitude of I m d 
To reconstruct the synoptic-scale flow pattern, the coefficients«,,,have been determined 
from vector averaged daily mean salues The polygon spread out by the current meters has 
a maximum extension in west-east direction of 48 km, and 30 krn in north-south direction 
(see dotted line in Fig. I). The Rossby deformation radius, giving the horizontal scale for 
synoptic eddies, i. e. periods from days to months and scales of tens or some hundreds of 
kilometres (Ka m en ko v ic h, Kosh I y akov and Mon in [1986]) 
f-n 
amounts about 70 km in the NOAMP area (Coriolis parameter/^ 1.075 x 10 ‘I/s,depth of 
the ocean H = 4500 m and depth-averaged Brunt-Vaisala frequency ;V = 2.8 x 10 T/s). 
It is obvious that the streamfunction maps - reliable only inside the current meter 
polygon — cannot picture a synoptic vortex as a whole. The storms occurring during 
NOAMP I are labelled with A and B in Table 1. Figures 4 and 5 show streamfunction maps 
for both storms at 10, 70 and 200 m a. b. The vortex structure is evident at all levels. The 
stars mark the position of the moorings which measured the storm. In both cases, they are 
located in outer part of the vortex where the highest velocities arc expected. 
The deepest part of the BBL is the turbulent Ekman layer. Its height h c can be 
estimated as 
/i t = 0.4 x (ujf)