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Last month’s incident with an apparent Chinese surveillance balloon flying over North America produced an enormous public response in the U.S., including comments from political leaders and an amazing volume of coverage by the mainstream media.

The New York Times published well over 50 stories in February related to the balloon incident. The media coverage even included reporting that the balloon had been the subject of a comedy skit on TV.

Among the blizzard of stories was a largely that “a U.S. official speaking on condition of anonymity” stated that the purpose of the balloon was likely surveillance of military facilities in Guam and/or Hawaii.

While the media reporting was extensive and may have adequately covered the diplomatic and political aspects of the story, the basic reporting and explanation of the facts left much to be desired. Assertions were made by government spokespeople and anonymous officials without supporting evidence. Problematic issues were raised in the media reports that were left unresolved in the public discussion.

As a meteorologist I would like to share some background that may help readers to evaluate media claims and also explain why Hawaii may indeed be a likely target for balloon surveillance.

Soon after the balloon sighting was publicly reported, the Chinese government admitted ownership, but insisted that the balloon was being used for “meteorological research.” This claim was somewhat misstated in the media as a claim that the object was a “weather balloon” and this notion was widely ridiculed. Time magazine ”The Chinese Balloon Looks Nothing Like a Weather Balloon, Experts Say.”

Indeed, what we usually refer to as “weather balloons” hundreds of locations worldwide and carry instruments to perform routine measurements that provide the backbone of the atmospheric observations used to produce the daily weather forecasts.

At the ground the balloons are filled with helium to about 6 feet in diameter and then continually expand as they rise and experience lower atmospheric pressure. They may typically rise for about two hours attaining heights around 100,000 feet at which point the balloons burst.

The Chinese were almost certainly referring to another class of high-altitude balloons that are extensively used for scientific research by various countries. These “superpressure” balloons are designed to expand only to a particular size at which point they could remain airborne for periods of up to several weeks or even months.

An example is being applied now in international meteorological investigations of the atmosphere at heights around 60,000-70,000 feet. These balloons have a fully expanded diameter of nearly 50 feet and can carry much heavier payloads of instruments than the smaller “weather balloons.” Note that the Chinese balloon flying at about 60,000 feet.

The Strateole balloons do not have their own propulsion and will move with the wind. The altitude of the balloon is somewhat controllable, however, by having a separate chamber within the balloon filled with air (denser than the helium which fills most of the balloon) and then pumping air in or out.

This can allow a modest degree of horizontal control if the horizontal wind changes significantly with height, but such a balloon is always at the mercy of the winds. The Chinese balloon was almost certainly similar in its basic design and capabilities as the Strateole balloons used by the international science community.

A Balloon Over Montana

The Chinese balloon story in the media began when the unidentified balloon was seen over Billings, Montana, which it was noted is close to a major component of America’s nuclear arsenal. Public figures leaped to the conclusion that the balloon was spying on U.S. nuclear forces.

To me it seemed highly implausible that a balloon of this type could be guided to a particular location in Montana, given the complicated and ever changing winds at that height in the atmosphere.

The story gets more complicated as stated that the Chinese balloon was maneuverable in some mysterious manner, a claim . This issue remains unresolved in the public record but I very much doubt that the Chinese balloon had more maneuverability than the superpressure balloons familiar to international scientific researchers, such as Strateole.

From the perspective of a meteorologist, the unpredictability of the motion of long lived balloons gives them a rather limited value in military surveillance.

What were the Chinese really trying accomplish? I now return to the above noted view that the balloon actually targeted Guam and/or Hawaii. We cannot know all the intelligence that may have led to this conclusion, but the claim is very plausible and provides a more reasonable explanation for the Chinese actions.

Specifically, the winds at levels of 60,000 feet or higher typically have somewhat simpler behavior in the tropics than at higher latitudes, or in the lower atmosphere. Specifically the wind tends to be dominated by the east-west component and to be reasonably steady from day to day. This means that often, if not always, a balloon released in the tropics will keep close to its initial latitude even for multiple trips around the globe.

Problematic issues were raised in the media reports that were left unresolved.

Examples of tracks of Strateole balloons that were launched very close to the equator in the Maldives can be seen and . Remarkably, the initial understanding of this aspect of the high level winds in the tropics was due to an amateur scientist from Hawaii who analyzed observations after the 1883 Krakatoa eruption, a story I told in a 2021 article that appeared in Civil Beat.

The Chinese are suspected of launching their balloon from around 19 degrees North in their southernmost . They might have had a reasonable hope that their balloon would not stray too far north-south as it was blown eastward toward Hawaii.

But the winds are not completely predictable and there will be a substantial chance that the balloon could be caught up in higher-latitude weather systems and drawn out of the tropics. Indeed this in the case of the balloon shot down in February.

However, depending on the value of the intelligence the Chinese feel they may gain, we may well expect the unique wind patterns above us to be exploited again and that future balloon visitors may pass high over Hawaii.