[sliken]

Digging a giant crater localizes the destruction and consumes most of the energy An air burst doesn't bother digging a giant crater and has a larger fraction of it's energy dumped into the atmosphere for fireballs, high winds, and direct radiation.

[midoridensha]

I thought asteroids didn't normally produce any direct radiation; their explosions are purely from being superheated by the atmospheric friction. (Obviously, nuclear airbursts do produce a lot of radiation.)

[dredmorbius]

"Radiation" here refers to thermal radiation --- the direct radiant heat released through atmospheric friction and blast.

The shockwave itself is also radiant energy, in this case a kinetic overpressure wave.

Net impact effects are "wind blast, overpressure shock, thermal radiation, cratering, seismic shaking, ejecta deposition, and tsunami":

<https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/201...>

Remember that "radiation" simply refers to any effect that radiates outward from an initial point or source, say, a radiator. Yes, common parlance has abbreviated "ionizing nuclear radiation" as "radiation", but that's only one of numerous types of radiant energy.

[midoridensha]

When someone says "a nuclear bomb releases heat and radiation", the radiation they're referring to is not thermal radiation. You're being pedantic.

[dredmorbius]

The link I provided gives alternate usage. You might wish to reconsider your position.

[sliken]

Well potential energy is turned into kinetic energy, which heats up the asteroid. Any water, or gas inside could well result in an explosion.

Things like turning night into day release a fair bit of radiation, like light.

The Tunguska event is thought to be an airburst, that flattened many trees (80M or so), made an incredibly loud explosion, and it's claimed it was nearly as bright as the sun.

[midoridensha]

That's not radiation though. When people talk about "radiation", they don't mean light, they mean ionizing radiation, not everything across the entire EM spectrum.