World Viewpoint Tells a Story

I have just added videos which have been created from images captured from GOES 16 / 17 and Himawari 8. Each video is generated every 10 minutes and it shows the last 48 hours for each image type.

You can view the latest videos via this link.

Whilst just watching each video is fascinating, there is so much to see in each, especially the GOES 17 full disk images in visible light and even more so when captured just a few weeks after the summer equinox in the southern hemisphere.

GOES 17 Visible Light – 13-15 Jan 2021 (NZ Dates)

The only processing on the video is to drop the image size down from a resolution of 5424 x 5424 pixels to just 800 x 800, otherwise the file size for the video would be pretty large, plus it would take a significantly longer time to generate the video and even with an expensive 4k monitor, you’d not see the full detail.

The country and state boundaries have also been added which makes it a lot easier to work out where everything in.

The video clearly shows the day / night cycle over two days, 48 hours, but there is a lot more happening in the video.

Being just after the summer equinox in the southern hemisphere, you can see that the very southern part of the images shows that it never gets dark over Antarctica (within the Antarctic Circle). Similarly it is never getting light over the northern polar regions (within the Arctic Circle). A similar video captured in 5 months time will show the opposite. This is due to the combination of the earth being tilted at an angle of 23.5 degrees and where the earth is as it orbits the sun.

This also results in the start of the day sweeping from the bottom right of each frame and moving towards the top left. Again waiting 5 months for the summer equinox in the northern hemisphere will see this pattern reversed.

You will also notice that there is a bright area which tracks from the right to left in the bottom half of the images, following an arc which sees it moves upwards until it gets towards the middle of the day, then tracking downwards for the rest. This again is related to the tilt of the earth and at this time of the year it will be tracking along the Tropic of Capricorn. Wait 5 months and this will show an inverted pattern as it follows the Tropic of Cancer.

This is complex to visualize as you’re seeing a two dimensional view of a complex three dimensional system where you have the combination of:

  • The Earth
  • The Sun
  • The tilt of the Earth relative to its orbit around the Sun
  • The satellite

Again in the southern hemisphere you’ll see weather systems moving rapidly in a general west to east direction. These are known as the Roaring Forties and have been used for several hundred years by sailing ships to sail eastwards faster that at other longitudes.

Around the equator you’ll see an area with a relatively low amount of clouds, with multiple weather systems to the north and south of this area. This area is known as the Intertropical Convergence Zone, although historically it was called the doldrums. Here the globally predominantly northeast and southeast winds converge resulting in relatively calm areas which are not great for sailors, especially compared to areas like the Roaring Forties!

And finally you can see the sheer complexity of weather systems as they march across the earth, generally eastwards. There are systems which are thousands of kilometres across!

There is such a mixture of science and beauty in these images!

Leave a Reply