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A global view on earth's cloud circulation...

Written by Rainer Gerhards on 2007-06-17 at 11:45.

Visit "The Clouds" Homepage (more animations and information)!

You probably know that earth has cloud bends like other planets in the solar system (most notabely Jupiter and Saturn). If you watch at weather forecasters, you've probably seen some of these clouds come and go to your area. However, local (even nationwide) forecasters typically only show you a small part of the visible earth and only a few days of data at most.

Watch the animation below: it shows earth's cloud circulation during a full month (May 2007) and on a global scale. Note: you need to start the animation by clicking the "play" button in the player below - I've not auto-started it so that you are not distracted. Satellite data is taken from EUMETSAT, who thankfully makes images available free of charge to the general public.

What can be seen? You probably notice the big cloud bend along the equator. This is where sun shines very strong and a lot of clouds from due to evaporation. Winds in this area blow mostly easterly. These winds are called the "trade winds", a name that stems back to sailors in former centuries. They used the route along the equator to sail from Europe to America. In higher latitudes, we see the belt of the westerly winds.  These winds were used by the sailers to sail back from America to Europe. They do not blow as steady as the trade winds, but they are still quite reliable. In between these areas, there is the desert belt with only very little clouds and hence little rain. There is a third wind belt, the "polar easterlies", from the pole down to around the 60 degree of latitude. That belt can unfortunately not very well be seen in the animation.

Before I created that animation, I know that there are some wind / cloud systems on earth. But I have to admit that I was quite surprised at how good these can be observed. From first view, it looks like the forces creating these systems are quite similar to those on other planets. Now that I have started this animation project, I have become somewhat addicted. First of all, I'll try to cover at least a year's worth of pictures and animation. One should probably be able to see seasonal effects. Secondly, I've begun to dig deeper on why these wind belts exists. I hopefully will be able to provide further information and animations once I have covered the basics.

I would deeply appreciate any feedback - be it questions, new ideas, corrections, suggestions - whatever. I have set up a forum are on my side. You may use this thread as a starting point.

There is also a high-resolution version of of earth's cloud circulation available. That version offers considerable extra detail, but comes at the cost of a 25 MB download. If you have a fast Internet connection (or be patient), I highly recommend having a look at it.

You probably notice that the area of earth shown covers Europe, parts of Asia and Africa. That stems back to the data source: the satellite is used for weather forecasting in that area. If you know of similar (free to use) images for America, please let me know: I'd really love to create a similar animation. In fact, one should be able to see clouds moving all around earth if two different sets of images could be aquired.

Copyright © 2007 Rainer Gerhards
Satellite Pictures: Copyright © 2007 EUMETSAT, Animation: Rainer Gerhards
All other Pictures: Rainer Gerhards
Last Update: 2007-07-09

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