the latitude has to do with patterns of rising and descending air. the hot air where the sun is striking at the highest angle (directly above) at the equator rises, which means that air has to fall somewhere else (high pressure). that zone is to the north and south, in the subtropical zone. in the northern hemisphere that zone shifts south the winter, because the peak radiation is moving toward the tropic of capricorn. this means there is a dry season in the monsoonal zone, and a wet season in southern temperate zone as the high pressure shifts south.

Why it forms, I have no idea. I’d guess it has something to do with the edge of a continent, but why does it form off California instead of Oregon, or British Columbia?

Speaking of world-wide visualizations, I’ve read that most of Africa is rather higher than the non-mountainous parts of other continents – that the continent is essentially one big plateau with some mountains along the East African Rift Zone. Before I read that, I had no clue that was true (or if it actually is). Nor do I have any idea why, in plate-tectonic terms, that should be so, or what effect it causes on Africa’s climate.

Another bit of ignorance was dispelled after reading an article in The Economist, where I read that some rather significant part of inland Brazil is not rain forest, but is actually potentially quite rich farmland – and potentially dust bowl if managed wrong.