Question for a planet I'm designing

[Sen]

My friend inspired me to make a planet that had one, immense ocean that filled an equally tremendous impact crater (or was terraformed into it, either way, the planet had a very big, circular ocean.) As I started to design the world, I ringed the ocean with vegitation that gradually thined until at the opposite side of the planet, it is desert. Would this be a realistic rendering of such a world? What would be the climatological effects of having a singel, roughly circular ocean be? The planet is not tidally locked, and orbits a Sol-like star at roughly the same distance as Earth, with a similar atmosphere and gravity.

[BobHegwood]

Wouldn't it depend on the size of the ocean?
I mean, if the crater was fairly small, then your logic pertains.
But, if the crater covered half the planet, it wouldn't apply, would it?

[selden]

Some questions to consider for your planet's design:

How does water get from the crater-ocean to the rest of the planet?
e.g. what direction is downwind?
Are there outflowing rivers?
How high are the crater's walls?
Is their height uniform?

How does water return from the rest of the planet to the crater-ocean?
Are there rivers?
Where do they flow? i.e. what direction is downhill?

[eburacum45]

This page has a diagram which shows the direction of winds on Earth due to atmospheric circulation.
http://www.auf.asn.au/meteorology/section4.html
Overlay this diagram on your crater-world, and imagine the effects of the prevailing winds on the distribution of water vapour; the wind will blow the rain further in certain latitudes. Note that the effects of high mountains, or crater walls, might change these patterns considerably.

You might get high mountains or volcanoes at the point on the planet opposite the impact; Mars seems to have them opposite the Hellas impact.