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OPeNDAP client for data analysis and visualization
F E R R E T OPeNDAP client for data analysis and visualization
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What is Ferret? Command line application
Developed for large, gridded model output Provides analysis and visualization Popular in ocean modeling community Customizable graphics Customizable analysis (external functions) Delayed evaluation environment
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What is “delayed evaluation”?
Data access occurs when data is needed. Lets you create variable definitions. Lets you think mathematically instead of programmatically Perfect for data access with network latency.
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Delayed Evaluation use tmpu_winter8586.cdf let g = 9.81 let p0 = 1000
let omega = 7.292e-5 let deg2rad = /180. let f = 2 * omega * sin(deg2rad*y[g=tmpu]) let/qui theta = tmpu*((p0/z[g=tmpu])^0.286) set var/title="Potential Temp"/unit=K theta shade/z=850 theta ! data access
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Ferret use of OPeNDAP Local file access through NetCDF
use coads_climatology Remote file access through OPeNDAP use “OPeNDAP URL” OPeNDAP provides data translation into the NetCDF API.
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Ferret tour yes? use coads_cliamtology yes? SHADE/L=1 SST
yes? GO fland
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Ferret tour yes? SHADE/L=1 AIRT-SST yes? GO fland
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Ferret tour yes? SHADE/LINE
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Ferret tour yes? SHADE/PALETTE=centered SST[L=1]
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Ferret capabilities Section plot (with split Z axis)
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Ferret capabilities Map projections
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Ferret capabilities Time series analasys
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Ferret capabilities Support for curvilinear model grids
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Ferret Documentation
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Tutorial: opening a dataset
prompt> ferret … yes? use coads_climatology yes? show data yes? show grid sst yes? shade sst[l=9]
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Tutorial: opening remote data
yes? cancel data/all yes? use “ yes? show data … yes? show grid sst yes? shade sst[l=9]
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Tutorial: regions Ferret converts world coordinate bounds into OPeNDAP index bounds yes? set region/x=100w:0e/y=10n:60n yes? set region/t=“15-sep” yes? shade sst … yes? can region yes? set region/i=120:170/y=50:75/l=9
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Tutorial: strides Ferret and OPeNDAP understand how to use NetCDF ‘strides’. Create images from a fraction of the data. Greatly reduces network traffic. yes? can region yes? shade sst[i=1:180:4,j=1:90:4,l=9]
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Tutorial: tranformations
Ferret can perform axis ‘transormations’ min, max, ave, var, sum, ngd yes? shade yes? shade yes? can data/all yes? use yes? show grid yes? plot
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Tutorial: regridding Ferret can regrid data
yes? use levitus_climatology yes? show data … yes? shade sst[d=1] – temp[d=2] yes? let sst_on_levitus = sst[d=1,gxy=temp[d=2]] yes? set region/k=1/l=1 yes? shade sst_on_levitus – temp[d=2]
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Tutorial: putting it all together
yes? use " yes? show data … yes? show grid GISST22_NOR1DG_6190 yes? shade GISST22_NOR1DG_6190[k=1]
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Tutorial: putting it all together
yes? use climatological_axes yes? define axis/x=180:540:1/modulo/edge/unit=degree x_1deg yes? define axis/y=-90:90:1/edge/unit=degree y_1deg yes? define grid/x=x_1deg/y=y_1deg/t=month_reg g_1deg_clim yes? use " yes? let my_gisst = if GISST22_NOR1DG_6190[d=2] GT -300 then GISST22_NOR1DG_6190[d=2]
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Tutorial: putting it all together
yes? let reverse_j=181-j[gy=g_1deg_clim] yes? let gisst_rev_j = samplej(my_gisst,reverse_j) yes? let grid_var = 0 * i[gx=g_1deg_clim] + 0 * j[gy=g_1deg_clim] + 0 * l[gt=g_1deg_clim] yes? let gisst = reshape(gisst_rev_j,grid_var) yes? set var/title="GISST temperature"/units="Deg C" gisst
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Tutorial: putting it all together
yes? shade gisst[l=3] yes? use coads_climatology yes? show grid gisst yes? show grid sst yes? let coads_1deg_sst sst[d=coads_climatology,g=gisst] yes? show grid coads_1deg_sst yes? shade/l=3 gisst-coads_1deg_sst
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