Hovmöller diagram

AHovmöller diagramis a common way ofplottingmeteorologicaldata to highlight the behavior ofwaves,particularlytropical waves.Theaxesof Hovmöller diagrams depict changes over time of scalar quantities such astemperature,density,and other values of constituents in theatmosphereorocean,such as depth, height, or pressure. Typically in that case, time is recorded along theabscissa, or x-axis,while 'vertical' values (of depth, height, pressure, etc.) are plotted along theordinate, or y-axis.

This Hovmöller diagram records arunning mean valueofoutgoing longwave radiation,OLR, which produces contour-values (here shown from +3 to –3) of theMadden–Julian oscillation,MJO. Here, time increases from top to bottom, i.e., vertically, along the ordinate, or y-axis; while the oscillation contours are oriented from left to right, horizontally, on the abscissa, or x-axis. Thus, overcalendartime from April to September, the movements of any specific contour-value are depicted as from west to east—that is, from 20E longitude to 10W longitude.

The alternate orientation of axes may also be used, as a Hovmöller diagram may be plotted forlongitudeorlatitudeon the abscissa and for (advancing) time on the ordinate; then the contour values of a named physicalfieldmay be presented through color or shading.

The Hovmöller diagram was introduced byErnest Aabo Hovmöller(1912–2008), aDanishmeteorologist, in a paper published in 1949.

See also

• Tropical wave
• Heat map

External links

• An example Hovmöller diagram showing rainfall