What I want to know is, does the Earth’s rotation have more of a bearing on the direction of the volcanic clouds than wind currents? Is it the planet’s rotation which creates the air currents, or is that just a temperature thing?
ultra-Short version: The temperature difference between equator and poles causes north-south wind. The Earth’s eastwards rotation transforms that into a predominantly eastward net wind. The volcanic clouds (and conventional clouds too) go where the wind carries them. No other material force is acting on them.
ETA on IA’s last point. The atmosphere as a whole is in sync with the planet’s rotation. The net wind is the expression of the amount of non-sync. And the net wind is stronger at altitude (see “jet stream”) precisely because it’s best coupled to the ground at ground level. And some (not all) of what we call “weather” can be attributed to drag effects and turbulence at large (multi-hundred mile) scale.
Nice job. Let’s note that “predominantly eastward” is latitude-specific. (These are tje “prevailing westerlies” of popular terminology – a “west wind” or “westerly” is one that comes from the west, relative to where you are.)
In the tropics and near the poles, the counter-flow occurs – predominantly east-to-west winds. The southerly set of these (in the Northern Hemisphere) are the “Trade Winds” of song and story. So what you end up with is winds blowing mostly from temperate-zone America to Europe and mostly from North Africa to the Caribbean, setting up a large, stable, non-catastrophic vortex over the Atlantic centered on Bermuda and the Sargasso Sea. Similar, though not so obvious, effects occur over the South Atlantic, North and South Pacific, and Indian Oceans.
A related question: I was watching the news this morning, and they showed diagrams confirming the prevailing easterly travel of the smoke and ash – and then followed up by saying Canadian flights may start canceling today as the plume hits North America. None of the experts or maps I’ve seen indicated westward movement of the plume. What’s going on here?
And, by the way, I just had to say this is a marvelous thread title/dopername combo:
Weather Influence of Iceland Volcano