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NCL Graphics: Time vs. Longitude (Hovmueller)

Hovmueller Plot Templates

hov_1.ncl: Default black and white Hovmueller plot.

gsn_csm_hov is the plot interface that creates Hovmueller diagrams.

hov_2.ncl: Reverses Y-axis to indicate elapsed time and changes the angle of the contour labels, and draws a zero line contour.

trYReverse = True, Reverses the y-axis.

cnLineLabelAngleF = 0.0, Changes the angle of the contour labels.

gsnContourZeroLineThicknessF doubles the thickness of the zero contour.

hov_3.ncl: Select Pacific region through coordinate subscripting, and hatches all contours, and draws a zero line contour.

ShadeLtGtContour is the shea utility function that shades the contours from -4 to 4. Note: ShadeLtGtContour has been superceded by the more versatile gsn_contour_shade. We recommend you use this instead.

A Python version of this projection is available here.

hov_4.ncl: Manually sets the contour labels and explicitly defines x-axis.

cnLevelSelectionMode = "ManualLevels"
cnMinLevelValF = -10.
cnMaxLevelValF = 10.
Manually sets the contour labels.

tmYLMode = "Explicit"
tmYLValues = (/ 0. , 30., 61., 89., 120., 150. /)
tmYLLabels = (/"DEC","JAN","FEB","MAR","APR","MAY" /)
Explicitly sets the x-axis labels.

hov_5.ncl: Creates a color plot.

cnFillOn = True, Turns on the color fill.

See the color example page for lots of ways of dealing with color.

hov_6.ncl: Creates a plot with the longitudes centered at 90W vice 180.

gsnMajorLonSpacing = 90.
Spaces out the longitude labels every 90 degrees. The default for this plot would be 60 degrees.

hov_7.ncl: Creates a plot with special month labels on the Y axis.

In this example, the minor tickmarks are treated as major tickmarks and vice versa. Several tickmark resources are used to place month labels inbetween the minor tickmarks.
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