Was the Chinese Balloon on A Spy Mission? Meteorologists Can Help Determine the Answer

There has been a lot of media coverage about the Chinese balloon that has been flying over the U.S., and which was shot down today.

Was it a spy balloon deliberately flown over the U.S., or was it an errant weather/research balloon?

Meteorologists with modern analysis tools can help answer the question.

The balloon was initially discovered at around 60,000 ft above Billings, Montana.

A key issue was whether this balloon was being controlled actively by China or drifting with the winds as claimed by Chinese authorities.

So understanding the path taken by the balloon is important.  Could this have happened by “accident”?

 NOAA has a wonderful system called Hyplit that allows one to calculate air trajectories over time.   (An air trajectory is the three-dimensional path of an air parcel over time).  You can think of an air parcel as the air inside a balloon.

Hysplit allows one to calculate back-trajectories, which tell one where some air at a point came from.  So we can start from a point at 60,000 ft over Montana and trace back the air reaching that point.

If an air parcel over Montana can be traced back to China, it could be an errant balloon.  If not, then the balloon had to be controlled, ascending or descending to put the balloon in different wind environments, thus allowing the craft to move in various directions.

Well, here are the backward trajectories for air over Billings at several elevations (16000 18,000, and 20,000 meters) at 2 PM on February 1.   18,000 meters is about 60000 ft.   The air trajectory ending at 60,000 ft (again 18,000 meters) did pass over southern China at an elevation of around 20,000 meters (66,000 ft).   Air parcels ending up higher over Montana could be traced back to the California coast.

What about trajectories ending up at lower elevations over Montana (10,000, 12000, and 14000 meters), roughly 33,000 to 46,000 ft? They started over China as well (see below).

Lower-level trajectories?  Only one ending at 8000 meters over Billings could have originated in China.

So was this some kind of accident?   

Chinese meteorologists would have known that any balloon released over China for a range of elevations would have reached the U.S.   And they could have selected where in the U.S. by moving the balloon up and down, or choosing different locations in China. 

If the balloon was launched with no ability to control height, they knew it would reach the US once it got to 8000 meters or more.  If they had up-and-down control (which one might assume considering the size and instrumentation on the balloon), they easily could have avoided reaching the U.S. by bringing the balloon down to lower elevations.

I will let you judge whether this was an accident.

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