The Hovmöller diagram was invented by Danish meteorologist Ernest Aabo Hovmöller (1912-2008). Typically, time is displayed on the ordinate (y-axis) and geolocation on the abscissa (x-axis). They are commonly used in meteorology and oceanography.

Let's create a Hovmöller of sea surface temperature (SST) from the Pacific Ocean to observe El Niño/La Niña-Southern Oscillation.

• In the Data Choosers tree's URLs node, enter the dods://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/noaa.ersst/sst.mnmean.nc URL and click the Add Source button.
• In the Field Selector's Data Sources panel, right-click the SST datasource and select Properties dialog.
• Click on the Times tab, select the Use Selected menu item and select a time range from January 1997 to December 1998 and click the Apply button.
• Click on the Spatial Subset tab and select a region in the equatorial Pacific Ocean from Mexico to Hawaii and click the OK button.
• In the Fields panel, select the Monthly Means of Sea Surface Temperature field.
• In the Displays panel, expand the Hovmoller tab and select Time-Longitude (Contours) then click the Create Display button.
• Modify the contour labeling by clicking in the Contour Change button. Choose a contour interval of 1 degree Celsius.
• Modify the color table by clicking the Color table default button. Change the range from 15 to 32.
• Can you see the El Niño/La Niña-Southern Oscillation?

Unidata IDV Workshop for version 6.3 > Accessing and Displaying Data > Working with Gridded Data