Thrust in the wind

October 24, 2005 10:42 AM

Why is there more wind in Autumn?

I've always noticed that as summer is ending, the wind picks up considerably. And it seems that all over the web, many, including NASA, agree that there is more wind and more stormy weather in Autumn. But I can't seem to find an explanation why. Is it air pressure? Temperature? The magnetosphere? What?

posted by poweredbybeard to Science & Nature (7 answers total)

the basic idea is that the poles get cold quick. the is a source of great difference in the atmosphere and it is differences-btwn temperatures and pressures (temperature and pressure being linked)--that cause wind.
posted by alkupe at 11:07 AM on October 24, 2005

Not sure about why, but the average wind speed in lots of American cities is significantly higher in the winter than in the summer.
posted by driveler at 11:08 AM on October 24, 2005

Best answer: I believe it is simply the fact that the seasons are changing.

Cold air/water sinks, warm air/water rises.

The northern hemishpere begins to tilt away from the sun and thus cools, the air drops. This change in temperature stirs things up, along the line of what alkupe was saying. The same thing happens with water.

Ahh, the 'cycle' of life.
posted by clgregor at 11:15 AM on October 24, 2005

At North American latitudes, there's more wind in winter than in summer; the wind picks up throughout the fall. The reason different seasons have different wind speeds is because temperature changes drive pressure and wind speed.
posted by nicwolff at 11:29 AM on October 24, 2005

Response by poster: thanks so far, folks, esp. clgregor - but "the change in temperature stirs things up" is a bit vague... ?

how does a change in temp cause wind? is it because of the way that warm air rising is replaced with cold air? and if so, why is this sustained for a period of months (earth core temp evaporating?)? does cold air from the poles move toward the centre, and if so, is this related to air pressure?

yes, i am an earth sciences "n00b," to use the scientific parlance.
posted by poweredbybeard at 12:47 PM on October 24, 2005

Best answer: The sun heats the land; the land heats the air, which rises, leaving a low-pressure zone at ground level. Cooler air moves across the land to fill the partial vacuum - not all the way from the poles, because the rotation of the Earth breaks up the flow, but in three great "cells" on each side of the equator:



When you're at one of the latitudes where the cells meet, the predominant motion of the air is vertical, and local winds will be weak and inconstant. When you're under the middle of a cell, winds will be steady and strong.

The whole system moves north and south over the planet as the seasons change, so you can stay in one place and see a cyclic seasonal pattern.
posted by nicwolff at 2:55 PM on October 24, 2005

I live in western Colorado and it seems to me that the wind was much more fierce in the spring than it has been this fall. So, out here in the desert, it does not seem true that there is more wind in autumn.
posted by madstop1 at 4:52 PM on October 24, 2005