Talking About The Weather, Part One

re: Talking About The Weather, Part One

Bahbar — Thu, 02 Aug 2007 18:22:59 GMT

> If the droplets get big enough then they become denser than the surrounding atmosphere and fall back to earth in the form of rain.

I am not a meteorologist by any means, but that notion that density increases as droplets get bigger is wrong.

As soon as the water condenses, its density is pretty much fixed. It is immediately denser than the atmosphere too. It does not get "denser" as the droplets merge. So what is making the condensed water stay in the air ? winds ?

re: Talking About The Weather, Part One

Eric Lippert — Thu, 02 Aug 2007 19:18:57 GMT

OK, good point.

Look at it this way. The amount a droplet is influenced by updrafts is proportional to both its surface area (which is being pushed by the draft) and its mass (which gives it resistance to changing direction). But the amount it is influenced by gravity is proportional only to the mass.

The mass is proportional to volume.

The volume rises as the cube of the radius of the droplet. The surface area rises as the square. So as the droplet grows, the amount of loft it can get from an updraft gets less and less, because its area is not increasing nearly as fast as its mass.

re: Talking About The Weather, Part One

BigTuna — Thu, 02 Aug 2007 19:25:19 GMT

> So what is making the condensed water stay in the air ? winds ?

If I'm remembering flight school correctly, wind is indeed the answer. Raindrops condense as parcels of warmer surface air are lifted and cooled in the updraft of a thunderstorm. The raindrops continue to condense and merge with each other until they become too heavy for the air column to support. The stronger an updraft is, the larger the raindrops will be.

Eric - please delete this post if I'm spoiling any secrets that you're saving for followup posts. Glad to see a fellow coder interested in meteorology!

re: Talking About The Weather, Part One

Pascal — Thu, 02 Aug 2007 20:03:16 GMT

Well I think water molecules have a strong magnetic polarity, and moving them up and down creates a inducted current .

This current strips some electrons in the air, slowly building up a charge difference.

When the charge is high enough - BLAM, the air becomes conductor and a lightning occurs.

So I think the clouds are turning mechanical energy (the vapour going up) into electrical energy until it becomes a storm and discharge to the ground.

Does it make sense?

re: Talking About The Weather, Part One

Fluvial — Thu, 02 Aug 2007 23:56:42 GMT

One of my best friends is getting her PhD in Atmospheric Science so I shall present this question to her and get back to you with a formal answer from a real live scientist.

Carry on.

re: Talking About The Weather, Part One

Harold — Fri, 03 Aug 2007 05:57:25 GMT

Suggestion for part n: forget about relative humidity, it's all about the dew point.

re: Talking About The Weather, Part One

dietas — Wed, 13 Feb 2008 19:26:09 GMT

Eager to read the Part 2 of this post.