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gsn_csm_contour_map_overlay

Creates and draws two contour plots over a map.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"

	function gsn_csm_contour_map_overlay (
		wks  [1] : graphic,  
		data1    : numeric,  
		data2    : numeric,  
		res1 [1] : logical,  
		res2 [1] : logical   
	)

	return_val [1] :  graphic

Arguments

wks

A Workstation identifier. The identifier is one returned either from calling gsn_open_wks or calling create to create a Workstation object.

data1

The first set of data to contour; must be one or two-dimensional.

data2

The second set of data to contour; must be one or two-dimensional.

res1

A variable containing an optional list of plot resources, attached as attributes, to be applied to the first set of contour data and/or the map plot. Set this value to True if you want the attached attributes to be applied, and False if you either don't have any resources to set, or you don't want the resources applied.

res2

A variable containing an optional list of plot resources, attached as attributes, to be applied to the second set of contour data. Set to True if you want the attached attributes to be applied, and False if you either don't have any resources to set, or you don't want the resources applied. Not that this resource is for the second contour plot only, and should not have any map ("mp") resources attached to it.

Return value

A scalar id of the map created is returned. The id of the first contour plot is returned as an attribute called contour and the id of the second contour plot as an attribute called contour2. This is useful if you want to use setvalues to change some data or contour options after this function has been called.

Description

This function creates and draws two separate contour plots over a map on the given workstation. The default projection is a cylindrical equidistant, which you can override by setting the mpProjection resource.

In order for the contours to be overlaid correctly on the map, please see the document "Overlaying data on a map".

The special resource gsnAddCyclic will be set to True so that a cyclic point will be added to the data. Set this resource to False if your data is not cyclic, or if you have already added the cyclic point in another fashion.

If data1 or data2 have a _FillValue attribute, these values will be used as a missing value.

If the resource cnFillOn is set to True, then the following will happen automatically:

• a labelbar will be automatically added (default horizontal)
• contour lines and line labels will be turned off
• the contour information label will be turned off

If you want to turn the labelbar off, set lbLabelBarOn to False.

For the map, the following will happen automatically:

• the continents will be colored gray
• the continental outlines will be turned off
• the latitude/longitude locations will be labeled
• the tickmarks will point outward (cylindrical equidistant map only)

If the map projection is cylindrical equidist, and the special GSN resource gsnZonalMean is set to True, then a zonal mean XY plot will be drawn next to the main plot. gsnZonalMeanXMaxF and gsnZonalMeanXMinF allow the user to change the X-axis of the zonal average plot. gsnZonalMeanYRefLine sets the value that the reference line will be drawn at on the zonal average plot, the default value = 0.

If data1 has an attribute called "long_name", and gsnLeftString hasn't explicitly been set, then the value of this attribute is used for the left string title.

If data has an attribute called "units", and gsnRightString hasn't explicitly been set, then the value of this attribute is used for the right string title.

To maximize the area that the plot is drawn in, set the special resource gsnMaximize to True.

See Also

gsn_contour, gsn_csm_contour, gsn_csm_contour_map, gsn_csm_contour_map_ce, gsn_csm_contour_map_polar
Special gsn resources

Examples

For some application examples, see:

• "conOncon_2.ncl" (view example)