Taylor diagrams provide a visual framework for comparing model results to a reference model or, most commonly, to observations. The plotted values are generally derived from monthly or seasonal climatological means of one or more variables. Because the different variables may have widely varying numerical values the model results are normalized by the reference variables. The ratio of the normalized variances indicates the relative amplitude of the model and observed variations. The pertinent statistics are the weighted pattern correlation (pattern_cor) and the normalized root-mean-square (RMS) differences.
A four-page pdf document, "Taylor Diagram Primer", by Karl Taylor, is available. This summarizes the important aspects of these useful plots.
Karl E. Taylor Summarizing multiple aspects of model performance in a single diagram JGR, vol 106, no. D7, 7183-7192, April 16, 2001.==================================================================
The documentation for the taylor diagram function is not complete. ==================================================================
The following examples use taylor_diagram.ncl to generate the background upon which the normalized statistics are plotted. The advantage of using the normalized version of the Taylor diagram is that variables with widely varying variances can be viewed on one figure.
The taylor_diagram function is prototyped as follows:
function taylor_diagram ( wks:graphic \ ; pre-created workstation , RATIO[*][*]:numeric \ ; 2d array: ratios , CC[*][*]:numeric \ ; 2d array: pattern correlation , rOpts:logical) ; scalar to which attributes ; are assignedGiven the following, the "taylor_diagram" will create the Taylor diagram. The correlations are assumed to range from 0 to 1 inclusive.
RATIO: ratio of the standardized variances
CC: pattern correlation
rOpts: graphical options
By default, the function can handle up to 10 variable comparisons. Different colors and markers are used to differentiate between different models/cases. The 10 default colors and markers are:
Markers = (/ 4, 6, 8, 0, 9, 12, 7, 2, 11, 16/) ; Marker Indices Colors = (/ "red" , "blue" , "green" , "cyan" , "orange" \ , "turquoise", "brown", "yellow", "purple", "black" /)The markers and colors can readily be changed by the user.
The taylor_diagram plot options are activated by setting the option argument, (say) "opt", to True and setting various attributes. The user specified attribute options include:
opt = True ; taylor diagram with options opt@tiMainString = "......" ; title opt@Markers = (/ ... /) ; markers opt@Colors = (/ ... /) ; colors opt@caseLabels = (/ ... /) ; case Labels opt@varLabels = (/ ... /) ; variable Labels opt@caseLabelsFontHeightF = ; caseLabels size [default=0.12 ] opt@varLabelsFontHeightF = ; varLabels size [default=0.013 ] opt@varLabelsYloc = ; Move location of variable labels ; [default=0.45] opt@gsMarkerSizeF = ; marker size [default=0.0085] ; BACKGROUND options opt@stnRad = (/ ... /) ; additional standard radii opt@ccRays = (/ ... /) ; correlation rays opt@centerDiffRMS = True ; RMS 'circles' opt@ccRays_color = "LightGray" ; default is black opt@centerDiffRMS_color = "LightGray" ; default is black ; OTHER recognized options opt@taylorFrame = False ; do not advance frame [default is True]The examples illustrate the use of most of these options.
The procedure for creating the CAM Taylor table is taylor_metrics_table.ncl. This procedure may be rewritten as needs develop.
The taylor_metrics_table procedure is prototyped as follows:
procedure taylor_metrics_table(mfname:string \ ; plot name ,varNames[*]:string \ ; variable names ,cases[*]:string \ ; case (model) names ,seasons[*]:string \ ; season names ,values[*][*][*]:numeric \ ; 3d array w values ,opt:logical ) ; options
There are some options but as of now, they are limited. The taylor_metrics_table plot options are activated by setting the option argument, (say) "opt", to True and setting various attributes. The user specified attribute options include:
opt = True ; taylor metric table with options opt@tiMainString = "......" ; title [default="CAM METRICS"] ; make roughly the same length opt@color0 = ; this will have to be improved. ; see example.=====================================================================
If a "bug" is suspected in "taylor_diagram" or "taylor_metrics_table", create:
[a] a concise description of the problem
[b] a clean test script
[c] make data available