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We launched a weather balloon where one of the sensors was an accelerometer. The data from it show all parts of the flight (1 launch (0 m), 3 bursts of the balloon (35,800 m), 4 landing (0 M)).

We also measured the temperature, which shows that the balloon left the tropopause and entered the stratosphere at 9:20 a.m. at an altitude of 18 km (3). What is interesting is that the data from the accelerometer shows that at that moment the balloon experienced a relatively large shock and subsequently stopped flapping as much as it did in the troposphere. What is it caused by?

The Z axis was pointing up in the direction of flight.

The balloon was launched on 17.9. 2021 from the Czech Republic.

Acceleration

  1. Launch
  2. The end of the tropopause and the beginning of the stratosphere
  3. Balloon burst
  4. Landing

Height Temperature UV Pressure

Update: In flight photo

balloon

There is a balloon at the top, a parachute in the middle and a small round probe at the bottom. When the balloon burst, everything fell together in a big mess.

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    $\begingroup$ Providing an excellent confirmation of air pressure (and density) vs altitude when it fell. Scroll down for graph. I never knew that lifting capacity does not decrease with altitude flying an expanding balloon, but it now makes sense. That's how manned balloons can go over 30,000 meters. $\endgroup$
    – Robert DiGiovanni
    Dec 3, 2022 at 13:25
  • $\begingroup$ Nice data. I don't understand the plot of the temperature though: why the big drop when it bursted? $\endgroup$
    – sophit
    Dec 3, 2022 at 21:50
  • $\begingroup$ Changes in temperature are caused by how the balloon passed through different layers of the atmosphere. It's easy to see when flying up. But the temperatures are @sophit very high there, because the probe was probably heated by the sun. On the descent, the same thing happened, but the temperatures dropped much lower because the probe was blown more by the wind and cooled down to the actual temperature that prevails in that location in the atmosphere. $\endgroup$
    – Saturn V
    Dec 4, 2022 at 7:44
  • $\begingroup$ I'm suspicious of the acceleration data. Do you know why X and Y are nearly constant but non-zero? Could it be off-axis? $\endgroup$
    – BowlOfRed
    Dec 5, 2022 at 4:31
  • $\begingroup$ @BowlOfRed Yes, I think that it is off-axis. I don't think there's any other reason why it should look like this. $\endgroup$
    – Saturn V
    Dec 5, 2022 at 7:20

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The balloon really seemed to settle down once it entered the stratosphere, and had larger changes in vertical velocity before that, and after bursting.

If I may assume there was a parachute recovery, then I would like to suggest interaction with variable winds as the cause. The balloon and its cargo were probably swinging back and forth, which, by changing drag profile, would affect the vertical velocity up and down.

The stratosphere is known to be a bit calmer, and, as the balloon approached burst, the tension on its skin may have been strong enough to better resist deformations, which would also affect its passage through the air.

What was very impressive is the constant rate of climb all the way up.
Congratulations on your flight and recovery of some very interesting information.

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  • $\begingroup$ Thanks for the reply. I updated the questions with a photo from the flight and another description. So you think the calming is due to the stratosphere being calmer? But what is the cause of the shock before entering the stratosphere (2)? The weirdest is the one in the Z axis. $\endgroup$
    – Saturn V
    Dec 3, 2022 at 11:34
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    $\begingroup$ @SaturnV probably some heavy turbulence at the interface of two atmospheric layers or a down draft. Curious how far did you have to go to recover it? $\endgroup$
    – Robert DiGiovanni
    Dec 3, 2022 at 13:31
  • $\begingroup$ The balloon landed about 100 km from the launch site. I also noticed that the same jolt probably happened on the way down between 10:47 and 10:57. $\endgroup$
    – Saturn V
    Dec 3, 2022 at 14:03
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    $\begingroup$ @SaturnV the spike on the Z axis might be consistent with the balloon being pulled sideways as it ascends/descends through a wind gradient. In that case z temporarily no longer points toward earth. As far as you traveled in ground distance, you must have had alot of wind. Getting a local airport METAR may be helpful for your next flight. $\endgroup$
    – Robert DiGiovanni
    Dec 3, 2022 at 17:10

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