Convective storms - an Apollo 9 view

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Celebrating the 50th anniversary of the moon landing with views of Earth from satellite and Apollo missions

Convective storms - an Apollo 9 view
Date & Time

By Martin Setvák  (CHMI)

When the first humans walked on the Moon on 21 July 1969, weather satellites were in their infancy. However, as the celebrations of Apollo 11 launch on 16 July and the landing on the Moon take place, we look back at images from an earlier Apollo mission and compare them to see how close they were to what is seen on satellite images today.

In 1969,  weather satellites were much less sophisticated than current satellites. The US operational weather satellite was Nimbus 3, (launched shortly after the Apollo 9 flight, on 14 April 14 1969), providing images at significantly lower quality than what we have become used to. See the two examples from the Nimbus-3 IDCS instrument, of storms above the US on 5 May 1969 and 18 May 1969 (Figures 1 and 2).

Figure 1: Nimbus-3, 5 May 1969 17:02 UTC. Credit: NASA
Figure 2: Nimbus-3, 18 May 1969 16:31 UTC. Credit: NASA

Therefore, at that time, manned spaceflights were the only opportunities to acquire first higher resolution images of clouds from space, including tops of convective storms.

The Project Apollo Archive, is an online resource for historical high resolution images, taken during the entire Apollo program (7 to 17), made available by NASA's Johnson Space Center. Some of the photos there show storm tops with all the features as we know them today, from viewing them with our more recent, high-tech satellites.

All the images below come from the earlier Apollo 9 mission, from Day 4 (March 06, 1969), orbit 46, taken between 17:10–17:20 UTC. They were taken during extra-vehicular activity (EVA) of the crew, from an altitude of about 200 km, using Hasselblad cameras on 70 mm SO-368 Ektachrome film. The images are not oriented with respect to the Earth’s poles. Note: the original images have been enhanced.

A storm with overshooting top and above-anvil cirrus plume

Figure 3

Figure 3: A storm with overshooting top and above-anvil cirrus plume. Credit: NASA

On Figure 3 (see original AS09-20-3071 image), top right of the Apollo 9 command module, is a storm (encircled by a red ellipse), which exhibits an overshooting top with adjacent, well-defined plume. The plumes (or more accurately 'above-anvil cirrus plumes', AACP, as known today) were revealed and documented much later. They were first described in 1982 by T. Fujita (based on aircraft photography observations), and about a decade later, by Setvák and Doswell, 1991 and Levizzani and Setvak, 1996, based on AVHRR imagery. Nowadays, the plumes are regarded as one of the storm-top features, closely related to storm’s severity, e.g.Bedka et al, 2018.

As that time NASA Nimbus satellites (as well as their ancestors, or Soviet contemporary satellites) were not able to provide the necessary resolution in their images to reveal similar phenomena, this image is very likely one of the first images (if not the very first one), documenting AACP.

Circular convective storm with a large overshooting top

Figure 4

Figure 4: Circular convective storm with a large overshooting top. Credit: NASA

Figure 4 (see original AS09-22-3374 image) shows a convective storm above Colombia, with a textbook overshooting top. Since this storm evolved in the tropics, near the equator, the wind shear was very weak, resulting in the almost circular appearance of the storm, with the overshooting top located almost in the centre of the storm’s anvil. As with the plumes, the overshooting tops are recently known to be closely related to the strength of storm updrafts, thus are frequently used as one of the storm strength indicators, typically using automated detection methods (e.g. Bedka and Khlopenkov, 2016).

Storm with overshooting top, jumping cirrus, plume, and a 'pancake cloud'

Figure 5

Figure 5: Storm with overshooting top, jumping cirrus, plume, and a 'pancake cloud'. Credit: NASA

Figure 5 (see original AS09-22-3375 image) shows a storm above north-west Brazil. As well as the large overshooting top (just right of the image centre), casting very nice shadows on the lower anvil clouds, and generating jumping cirrus (right of this overshooting top), the image very likely also shows the so-called 'pancake cloud' (left of the image centre). The oval-shaped shadow clearly indicates vertical detachment of the cirrus cloud casting the shadow from the anvil top, and its shape suggests that it is, indeed, the pancake cloud — one of the storm-top features predicted and observed only recently — e.g. Pao K. Wang, 2019 (in the recorded presentation there). Attached to it, spreading top-right of the suspected pancake cloud, is a weaker cirrus plume.

Storm with an above-anvil cirrus plume

Figure 6

Figure 6: Storm with an above-anvil cirrus plume. Credit: NASA

Figure 6 (see original AS09-19-3024 image) shows another storm above Brazil, in this case exhibiting a nice above-anvil cirrus plume. Given the slant view, vertical separation of the plume is obvious.

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