NCL Graphics: Plotting data on cylindrical equidistant (CE) projections

These functions all produce plots on a cylindrical equidistant map projection:

The functions below will also give you a cylindrical equidistant map plot by default, unless you set mpProjection to something other than "CylindricalEquidstant":

See the description at the top of the Map outlines examples page for information about a change to the behavior of the mpDataBaseVersion resource in NCL V6.4.0.

ce_1.ncl: A default cylindrical equidistant plot.

gsn_csm_contour_map_ce is plot interface that creates a cylindrical equidistant plot, but you can also use gsn_csm_contour_map.

ce_2.ncl: Adds some intrinsic labels and manually sets the contour values.

res@cnLevelSelectionMode = "ManualLevels"
res@cnMinLevelValF = -10.
res@cnMaxLevelValF = 35.
res@cnLevelSpacingF = 5., manually sets the contour levels.

res@tiMainString = "CCM2 T42 July"
res@gsnCenterString = "300 mb", Creates a title and center string label

res@cnInfoLabelOrthogonalPosF = -0.07 Moves the contour information label into the plot. This is useful when conserving space is needed. Note in plots that contain an automatic zonal average next to the CE plot, this value was found to be -0.17.

ce_3.ncl: This script shows how to plot a subregion of a map, and compares two kinds of map tickmark labels.

In order to plot a subregion, the map must be limited or "zoomed". For a cylindrical equidistant projection, one method to zoom in on a map area is by setting min/max lat/lon values:

res@mpMinLonF
res@mpMaxLonF
res@mpMinLatF
res@mpMaxLatF

To see what other methods exist and what projections they apply to, review the mpLimitMode documentation.

The first frame shows the default map tickmark labels. If you want the lat/lon labels to have have degree symbols and minutes, then set pmTickMarkDisplayMode = "Always". Generally, regional plots look better if you set this resource.

Note that if your data is only on a regional grid, you likely want set to gsnAddCyclic to False to avoid a longitude cyclic point from being added.

A Python version of this projection with major and minor ticks is available here.

A Python version of this projection with major ticks and no minor ticks is available here.

ce_4.ncl: Demonstrates vectors on a CE projection. The vector example page.

gsn_csm_vector_map_ce is the plot interface that draws vectors over a map.

vcMinDistanceF = 0.017, Thins the vectors
vcRefAnnoOrthogonalPosF = -1.0, Moves the reference vector up.

ce_5.ncl: Turns off the map fill and adds a side zonal average.

gsnZonalMean turns on the side zonal mean plot. This only works for contour plots. 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.

cnInfoLabelOn turns off the contour info label.

The placement of the line labels is controlled by the cnLineLabelPlacementMode resource. The default is random. Also demonstrated is the "computed" value.

mpFillOn = False, turns off the gray continents.

gsn_panel is the graphical interface that creates a panel plot. More panel examples are available.