Does a creature have to be directly in contact with the ground to be affected by the Destructive Wave spell?

Question

My character just got the destructive wave spell, which is a great AOE for close quarters combat (you designate who it affects). However, the other spell I use for that (spirit guardians) says it affects "Self (15-foot sphere)", while Destructive Wave says it affects "Self (30-foot radius)". The damage type is both Thunder and Radiant, both of which might be able to travel through the air. It says the wave "ripples" away from me, but again that could be in the air. It says it can knock opponents prone, making me wonder if they have to be standing.

Does a creature have to be directly in contact with the ground to be affected by the destructive wave spell? If so, does sitting in a tree, standing on a bar/table, or in a windowsill count as being in contact with the ground (as they would hopefully transmit the wave from the ground to the target)?

Answer 1

Destructive Wave affects a sphere around you.

You DM's interpretation of the spell may differ, but based on the text of the rules the spell affects a sphere. I take this interpretation from two pieces of textual information:

1. The range of the spell is given as "Self (30 foot radius)".
2. In the Areas of Effect section of the Spellcasting chapter (PHB 204), there are two different area types that use radius to calculate their area.
   • First is a Cylinder, which needs both a radius and a height.
   • Second is a sphere, which is the only area type that is defined only by it's radius.

This implies that, in the absence of further specification, any spell that has an area of effect measured only by radius affects a sphere. Since the description of Destructive Wave doesn't say anything like "targets of this spell must be on the ground", the spell affects everything in a sphere centered on you.