From AMS Glossary
(Abbreviated RHI.) A type of radar display on which the reflectivity or other properties of echoes are displayed as a function of range and elevation angle in polar coordinates.
The RHI may be produced by scanning the antenna in elevation with the azimuth fixed, or it may be composed of data from successive PPI displays at different elevation angles. It may be an intensity modulated display or may use a scale of colors to represent the values of the function displayed.