Thread: Widespread, shifting desert conditions

Hi,
I'm currently cooking an idea for a science fiction story (oh boy, imagined science, I know) involving a world where the climate changes drastically seasonally. As a simplified example, a planet with a wet season and a dry season, and here's the trick: while one hemisphere is suffering extensive drought, the other is living large on plenty of rain.

Problem is, I've only taken freshman Geology in college, and I don't know how this would come about. I know enough to know that the answer to this question probably involves wind conditions, but not enough to come up with a reasonable explanation for the unusual weather.

I was wondering if anybody could, at the very least, point me to a book that discusses issues such as these, or even better, explain some possible scenarios (in layman's terms) that might bring this situation about?

Thanks.

Mars partly fits your description. It has a very elliptic course around the sun, and in such a way then when it's summer on the southern hemisphere Mars is also closest to the sun. So in the southern hemisphere summers are more extreme then on the Northern one (which has summer when Mars is furthest from the sun). Same goes for the winters, they're more extreme in the South then in the North. This also happens on Earth, but here it's hardly noticable.

If you turn Mars into a larger planet with standing water (Mars is too small to hold an athmosphere, needs more mass) and make the elliptic course around the sun even more extreme, then you should get an interesting place. The North would be temperate all seasons, therefore able to have normal rainfall patterns and rivers. While the South alternates between extreme heat and extreme cold, never able to have standing water and normal rainfall except during it's short spring and autumn.

Hope it helps, sounds like an interesting project :wink:

The reason we get seasons on earth is because of the obliquity, or the tilt of our spin axis relative to the line that connects us to the sun. If our spin axis were perpendicular to the line between us and the sun we'd expect no seasons and the length of day and night would stay the same at a given location, also if it were parallel we'd expect no seasons but it would be permanently day in one hemisphere and permanently night in the other.

The more eccentric the orbit the greater the tidal heating, this might lead to a more geologically active planet.

You might also want to think about where the land masses, and ocean(s) are on your planet. You'd expect rain in the regions where air is rising and deserts where the air is sinking.

Off the top of my head I can't think of the scenario that would fit your fictional world, even without considering the seasonal variation! Think outside the box, perhaps there's some kind of outgassing going on that could bring chemical influences into the equation.......

p.s. I hope you've got a good story in mind, concentrate on the readability as opposed to the scientific integrity.

If you want a really far out scenario - here goes - consider the Earth - just as is is. A nearby Giant Star (just a few light years away) Goes super Nova - the Tremendous X-RAR Radiation kills Everything on ONe side of the Planet - All Plant life, animal life, The Other half remains Lush which (like the tropics) 'self replenishes' - The rest - all Dead - dessrtifies - THe Scenario would Probably only last a few thousand years at most but, hell, just how long will the story be? - You might have to do a bit of poking around but it could happen - Obviously the bulk of the planet shielded the half that was in night...

Thanks for the replies, very helpful.