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
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.
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.