Definition
A NEXRAD radar display option that overlays terrain elevation information on the weather radar image, allowing the pilot to see the shape and height of the ground beneath the weather being shown.
Plain English
A setting on the weather radar picture that adds the lay of the land underneath, so you can see hills, mountains, and valleys along with the weather.
Context Anchor
Seen on NEXRAD or aviation weather displays as a map layer, label, or display option.
Derivation
From the Greek topos, meaning 'place,' combined with graphein, 'to write or describe.' Topography literally means 'a description of a place' — in this case, the shape and elevation of the ground.
Why Pilots Care
Allows pilots to visualize terrain for safe navigation, especially in low visibility or mountainous areas.
Intuition Check
Do not read TOPO as a weather type. It is not rain, storms, or radar intensity; it is the land or terrain layer behind the weather picture.
Example Sentence 1
She turned on the TOPO overlay to see how close the storm cells were to the ridgeline along her planned route.
Example Sentence 2
NEXRAD combined with TOPO helps identify where precipitation is falling over varying terrain.