In the cooler temperatures, you're getting TWO effects that contribute to power. BOTH the fuel and the air are colder, so they are somewhat more dense. This adds up to more energy per fuel/air charge in the cylinders, so, you should see better acceleration. You pay for it though in increased fuel consumption.
As an aside, this phenomena was VERY apparent in the planes I used to fly. In the winter, our jets would just "leap" off the ground (but you couldn't fly as far without refueling). In the hot Texas summers, the old T-33s that I got my basic training in would almost not make it off the ground before we ran out of runway.
One of the preflight calculations you do is "takeoff distance". It needs to be less than the runway length or you don't go. And, a turbojet engine is really just a glorified diesel engine. (It will even burn diesel fuel - but it needs jet fuel for the anti-icing properties).
- Jack