I admit to looking at this just briefly, so I may be missing something. Is your variable curl_tau missing over land? In that case, in your definition of psi you should leave off the ELSE 0. The result will be missing wherever the expresssion curl_tau[x=160E:0@iin] is false. On this kind of definition there is an implied "ELSE missing"
Otherwise you need to apply a mask to the data as outlined in this FAQ about doing integration or averaging over irregular fields by applying a mask;
http://www.ferret.noaa.gov/Ferret/FAQ/analysis/avg_integ_irreg.html
For your case the mask would be a field which is 1 over water and missing over land.You could make such a variable from one of the topography data sets, choosing one which has a resolution similar to the grid your data is on
yes? use etopo20
yes? let mask = IF rose[d=etopo20,gxy=curl_tau[d=1]] LT 0 then 1
yes? shade mask ! Look at the plot to check the definition
Dr. Theodor Yemenis wrote:
I am trying to calculate and plot with FERRET the Sverdrup Streamfunction from the wind stress curl curl_tau
acording to the formel:
Psi = 1/beta Int_xlim(y) ^x curl(tau)dx, xlim (y) is the longitude of the boundary at each latitude.
I use the following definition (for the pacific ocean):
LET PSI = IF curl_tau[x=160E:0@iin] THEN (1/(beta*rho_ocean))*( (-1)*curl_tau[x=160E:0@iin] + curl_tau[x=160E:0@din] )/1E06 ELSE 0
fill PSI ; go land
the result is as in the attached GIF-image, but it is not sutisfing. I have the following problem:
- the islands(Hawaii, New Zeland, ...) and the Continent (Australia) disdurb the calculation (no streamfunction behind the land-boarders).
The problem is computing an indefinite integral in an area with irregular boundaries.
How can I solve this? Can someone help?
best regards
Theodor
