There has been a lot of media coverage of the Chinese hot air balloon that flew over the US and was shot down today.
Was it a spy balloon deliberately flying over the US, or was it a erroneous weather/research balloon?
Meteorologists with modern analytical tools can help answer the question.
The original hot air balloon was discovered at about 60,000 ft above Billings, Montana.
The key issue is whether the balloon is actively controlled by China or drifting with the wind as the Chinese government claims.
Therefore, understanding the path of the hot air balloon is very important. Could this have happened by “accident”?
NOAA has a great system called Hyplit that allows the calculation of air trajectories over time. (The air trajectory is the three-dimensional path of an air mass over time.) You can think of a parcel of air like the air inside a balloon.
Hysplit allows one to calculate retrograde orbit, which tells where some of the air at a point is coming from. So we can start from a point at 60,000 ft above Montana and trace the air back to that point.
If an air parcel through Montana can be traced back to China, it maybe is a false balloon. Otherwise, the balloon must be steered, ascending or descending to place the balloon in different windy environments, thus allowing the vehicle to move in different directions.
Well, this is the retrograde trajectory of the air over Billings at some altitude (16000 18,000 and 20,000 meters) at 2pm on February 1. 18,000 meters is about 60000 ft. The air orbit that ended at 60,000 ft (18,000 meters again) passed over southern China at an altitude of about 20,000 meters (66,000 ft). Air parcels ending higher than Montana can be traced back to the California coast.
What about the orbit that ends at altitudes lower than Montana (10,000, 12,000, and 14,000 meters), about 33,000 to 46,000 ft? They also start from China (see below).
Lower level orbital? Only an end at 8000 meters above the Billings could have originated in China.
So is this some kind of accident?
Chinese meteorologists already knew that any balloon dropped over China with a range of altitudes would reach the US. And they can choose the location in the US by moving the balloon up and down, or choose different locations in China.
If the balloon was launched without altitude control, they knew it would reach the US when it reached an altitude of 8,000 meters or more. If they had control over the up and down (which one might assume considering the size and instrumentation of the balloon) they could easily avoid going to America by bringing the balloon down lower altitude.
I’ll let you judge whether this was an accident or not.
