Hi Ferreters, I am trying to use ASCAT data downloaded from ftp://podaac.jpl.nasa.gov/pub/ocean_wind/ascat/preview/L2/12km/The files are netcdf files in curvilinear form, lat, lon and data are defined on a common abstract (x,y) grid.
It does not have a geophysical meaning. Ferret should be able to deal with such data. Indeed use ascat_20100111_005400_metopa_16755_eps_o_125_1018_ovw.l2.nc shade/d=1 WIND_SPEED, lon,lat; frame /file=shade.gif works and gives figure shade.gif.It does not look really bad.Now I want to put the data on a regular grid in geographic coordinates. The GFDL routine curv_to_rect_map
should be fine. yes? define axis/x=0:360:1/modulo/units=degrees xax yes? def axis/y=-85:85:1/units=degrees yax yes? let lonlatout = y[gy=yax] + x[gx=xax] yes? let lonin = lon[d=1] yes? let latin = lat[d=1] yes? let map = curv_to_rect_map ( lonin,latin,lonlatout,1) yes? save/clobber/file=curv_map.nc map (1 degree resolution) After some coffee: yes? cancel var/all yes? use curv_map.nc yes? let wo=curv_to_rect(wind_SPEED[d=1], map[d=2]) yes? shade wo; frame /file=curv_to_rect.gifBoth figures are in the attachment. The results have something to do with each other but they are also pretty different.
So my question:I do not really believe in the figure shade.gif. The reason is, that I may plot (lon,lat) pairs into the figure (plot/vs/ov lon,lat. In shade.gif there remain broad bands of coloured areas, in curv_to_rect.gif most data are covered by the symbols. So I guess, that the shade command implies some inappropriate interpolation. Does anyone have experience with plotting and processing such curviliear data?
It is great to have the interpolation tool curv_to_rect. But is there a chance to optimize the code for a speed up of the curv_to_rect_map routine? I would like to process years of data on a finer grid and it is very slow with 1 degree resolution.
Unfortunately the weights are changing for every file. Is there another and faster way to do this with ferret? Greetings, Martin Schmidt
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curv_to_rect.gif
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shade.gif
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